Societal and Ecological Impacts of Atmospheric Changes:Annotated Bibliography

A Contribution to the NSF FWI Changes, Attributions, and Impacts Working Group (CAWG)

Bill Gutowski, Iowa State University

Papers from AMBIO special issue: Climate Change and UV-B Impacts on Arctic Tundra and Polar Desert Ecosystems (Derived from the ACIA report)

AU Callaghan, TV, Bjorn, LO, Chernov, Y, Chapin, T, Christensen, TR, Huntley, B, Ims, RA, Johansson, M, Jolly, D, Jonasson, S, Matveyeva, N, Panikov, N, Oechel, W, Shaver, G, Elster, J, Henttonen, H, Laine, K, Taulavuori, K, Taulavuori, E, Zockler, CTI Biodiversity, distributions and adaptations of arctic species in the context of environmental changeSO AMBIOAB The individual of a species is the basic unit that responds to climate and UV-B changes, and it responds over a wide range of time scales. The diversity of animal, plant and microbial species appears to be low in the Arctic, and decreases from the boreal forests to the polar deserts of the extreme North but primitive species are particularly abundant. This latitudinal decline is associated with an increase in super-dominant species that occupy a wide range of habitats. Climate warming is expected to reduce the abundance and restrict the ranges of such species and to affect species at their northern range boundaries more than in the South: some Arctic animal and plant specialists could face extinction. Species most likely to expand into tundra are boreal species that currently exist as outlier populations in the Arctic. Many plant species have characteristics that allow them to survive short snow-free growing seasons, low solar angles, permafrost and low soil temperatures, low nutrient availability and physical disturbance. Many of these characteristics are likely to limit species' responses to climate warming, but mainly because of poor competitive ability compared with potential immigrant species. Terrestrial Arctic animals possess many adaptations that enable them to persist under a wide range of temperatures in the Arctic. Many escape unfavorable weather and resource shortage by winter dormancy or by migration. The biotic environment of Arctic animal species is relatively simple with few enemies, competitors, diseases, parasites and available food resources. Terrestrial Arctic animals are likely to be most vulnerable to warmer and drier summers, climatic changes that interfere with migration routes and staging areas, altered snow conditions and freeze-thaw cycles in winter, climate-induced disruption of the seasonal timing of reproduction and development, and influx of new competitors, predators, parasites and diseases. Arctic microorganisms are also well adapted to the Arctic's climate: some can metabolize at temperatures down to -39˚C. Cyanobacteria and algae have a wide range of adaptive strategies that allow them to avoid, or at least minimize UV injury. Microorganisms can tolerate most environmental conditions and they have short generation times which can facilitate rapid adaptation to new environments. In contrast, Arctic plant and animal species are very likely to change their distributions rather than evolve significantly in response to warming.TC 8, PD NOV, PY 2004, VL 33, IS 7, BP 404, EP 417, UT ISI:000225006300004

AU Callaghan, TV, Bjorn, LO, Chernov, Y, Chapin, T, Christensen, TR, Huntley, B, Ims, RA, Johansson, M, Jolly, D, Jonasson, S, Matveyeva, N, Panikov, N, Oechel, W, Shaver, G, Elster, J, Jonsdottir, IS, Laine, K, Taulavuori, K, Taulavuori, E, Zockler, CTI Responses to projected changes in climate and UV-B at the species levelSO AMBIO

AB Environmental manipulation experiments showed that species respond individualistically to each environmental-change variable. The greatest responses of plants were generally to nutrient, particularly nitrogen, addition. Summer warming experiments showed that woody plant responses were dominant and that mosses and lichens became less abundant. Responses to warming were controlled by moisture availability and snow cover. Many invertebrates increased population growth in response to summer warming, as long as desiccation was not induced. CO2 and UV-B enrichment experiments showed that plant and animal responses were small. However, some microorganisms and species of fungi were sensitive to increased UV-B and some intensive mutagenic actions could, perhaps, lead to unexpected epidemic outbreaks. Tundra soil heating, CO 2 enrichment and amendment with mineral nutrients generally accelerated microbial activity. Algae are likely to dominate cyanobacteria in milder climates. Expected increases in winter freeze-thaw cycles leading to ice-crust formation are likely to severely reduce winter survival rate and disrupt the population dynamics of many terrestrial animals. A deeper snow cover is likely to restrict access to winter pastures by reindeer/caribou and their ability to flee from predators while any earlier onset of the snow-free period is likely to stimulate increased plant growth. Initial species responses to climate change might occur at the sub-species level: an Arctic plant or animal species with high genetic/racial diversity has proved an ability to adapt to different environmental conditions in the past and is likely to do so also in the future. Indigenous knowledge, air photographs, satellite images and monitoring show that changes in the distributions of some species are already occurring: Arctic vegetation is becoming more shrubby and more productive, there have been recent changes in the ranges of caribou, and "new" species of insects and birds previously associated with areas south of the treeline have been recorded. In contrast, almost all Arctic breeding bird species are declining and models predict further quite dramatic reductions of the populations of tundra birds due to warming. Species-climate response surface models predict potential future ranges of current Arctic species that are often markedly reduced and displaced northwards in response to warming. In contrast, invertebrates and microorganisms are very likely to quickly expand their ranges northwards into the Arctic.TC 7 , PD NOV , PY 2004 , VL 33 , IS 7 , BP 418 , EP 435 , UT ISI:000225006300005

AU Callaghan, TV, Bjorn, LO, Chernov, Y, Chapin, T, Christensen, TR, Huntley, B, Ims, RA, Johansson, M, Jolly, D, Jonasson, S, Matveyeva, N, Panikov, N, Oechel, W, Shaver, G, Henttonen, HTI Effects on the structure of arctic ecosystems in the short- and long-term perspectivesSO AMBIOAB Species individualistic responses to warming and increased UV-B radiation are moderated by the responses of neighbors within communities, and trophic interactions within ecosystems. All of these responses lead to changes in ecosystem structure. Experimental manipulation of environmental factors expected to change at high latitudes showed that summer warming of tundra vegetation has generally led to smaller changes than fertilizer addition. Some of the factors manipulated have strong effects on the structure of Arctic ecosystems but the effects vary regionally, with the greatest response of plant and invertebrate communities being observed at the coldest locations. Arctic invertebrate communities are very likely to respond rapidly to warming whereas microbial biomass and nutrient stocks are more stable. Experimentally enhanced UV-B radiation altered the community composition of gram-negative bacteria and fungi, but not that of plants. Increased plant productivity due to warmer summers may dominate food-web dynamics. Trophic interactions of tundra and sub-Arctic forest plant-based food webs are centered on a few dominant animal species which often have cyclic population fluctuations that lead to extremely high peak abundances in some years. Population cycles of small rodents and insect defoliators such as the autumn moth affect the structure and diversity of tundra and forest-tundra vegetation and the viability of a number of specialist predators and parasites. Ice crusting in warmer winters is likely to reduce the accessibility of plant food to lemmings, while deep snow may protect them

from snow-surface predators. In Fennoscandia, there is evidence already for a pronounced shift in small rodent community structure and dynamics that have resulted in a decline of predators that specialize in feeding on small rodents. Climate is also likely to alter the role of insect pests in the birch forest system: warmer winters may increase survival of eggs and expand the range of the insects. Insects that harass reindeer in the summer are also likely to become more widespread, abundant and active during warmer summers while refuges for reindeer/caribou on glaciers and late snow patches will probably disappear.TC 7, PD NOV, PY 2004, VL 33, IS 7, BP 436, EP 447, UT ISI:000225006300006

AU Callaghan, TV, Bjorn, LO, Chernov, Y, Chapin, T, Christensen, TR, Huntley, B, Ims, RA, Johansson, M, Jolly, D, Jonasson, S, Matveyeva, N, Panikov, N, Oechel, W, Shaver, GTI Effects on the function of arctic ecosystems in the short- and long-term perspectivesSO AMBIOAB Historically, the function of Arctic ecosystems in terms of cycles of nutrients and carbon has led to low levels of primary production and exchanges of energy, water and greenhouse gases have led to low local and regional cooling. Sequestration of carbon from atmospheric CO, in extensive, cold organic soils and the high albedo from low, snow-covered vegetation have had impacts on regional climate. However, many aspects of the functioning of Arctic ecosystems are sensitive to changes in climate and its impacts on biodiversity. The current Arctic climate results in slow rates of organic matter decomposition. Arctic ecosystems therefore tend to accumulate organic matter and elements despite low inputs. As a result, soil-available elements like nitrogen and phosphorus are key limitations to increases in carbon fixation and further biomass and organic matter accumulation. Climate warming is expected to increase carbon and element turnover, particularly in soils, which may lead to initial losses of elements but eventual, slow recovery. Individual species and species diversity have clear impacts on element inputs and retention in Arctic ecosystems. Effects of increased CO2 and UV-B on whole ecosystems, on the other hand, are likely to be small although effects on plant tissue chemisty, decomposition and nitrogen fixation may become important in the long-term. Cycling of carbon in trace gas form is mainly as CO2 and CH4. Most carbon loss is in the form of CO2, produced by both plants and soil biota. Carbon emissions as methane from wet and moist tundra ecosystems are about 5% of emissions as CO2 and are responsive to warming in the absence of any other changes. Winter processes and vegetation type also affect CH4 emissions as well as exchanges of energy between biosphere and atmosphere. Arctic ecosystems exhibit the largest seasonal changes in energy exchange of any terrestrial ecosystem because of the large changes in albedo from late winter, when snow reflects most incoming radiation, to summer when the ecosystem absorbs most incoming radiation. Vegetation profoundly influences the water and energy exchange of Arctic ecosystems. Albedo during the period of snow cover declines from tundra to forest tundra to deciduous forest to evergreen forest. Shrubs and trees increase snow depth which in turn increases winter soil temperatures. Future changes in vegetation driven by climate change are therefore, very likely to profoundly alter regional climate.TC 9, PD NOV, PY 2004, VL 33, IS 7, BP 448, EP 458, UT ISI:000225006300007

AU Callaghan, TV, Bjorn, LO, Chernov, Y, Chapin, T, Christensen, TR, Huntley, B, Ims, RA, Johansson, M, Jolly, D, Jonasson, S, Matveyeva, N, Panikov, N, Oechel, W, Shaver, G, Schaphoff, S, Sitch, S, Zockler, CTI Synthesis of effects in four Arctic subregionsSO AMBIOAB An assessment of impacts on Arctic terrestrial ecosystems has emphasized geographical variability in responses of species and ecosystems to environmental change. This variability is usually associated with north-south gradients in climate, biodiversity, vegetation zones, and ecosystem structure and function. It is clear, however, that significant east-west variability in

environment, ecosystem structure and function, environmental history, and recent climate variability is also important. Some areas have cooled while others have become warmer. Also, east-west differences between geographical barriers of oceans, archipelagos and mountains have contributed significantly in the past to the ability of species and vegetation zones to relocate in response to climate changes, and they have created the isolation necessary for genetic differentiation of populations and biodiversity hot-spots to occur. These barriers will also affect the ability of species to relocate during projected future warming. To include this east-west variability and also to strike a balance between overgeneralization and overspecialization, the ACIA identified four major sub regions based on large-scale differences in weather and climate-shaping factors. Drawing on information, mostly model output that can be related to the four ACIA subregions, it is evident that geographical barriers to species re-location, particularly the distribution of landmasses and separation by seas, will affect the northwards shift in vegetation zones. The geographical constraints-or facilitation-of northward movement of vegetation zones will affect the future storage and release of carbon, and the exchange of energy and water between biosphere and atmosphere. In addition, differences in the ability of vegetation zones to re-locate will affect the biodiversity associated with each zone while the number of species threatened by climate change varies greatly between subregions with a significant hot-spot in Beringia. Overall, the subregional synthesis demonstrates the difficulty of generalizing projections of responses of ecosystem structure and function species loss, and biospheric feedbacks to the climate system for the whole Arctic region and implies a need for a far greater understanding of the spatial variability in the responses of terrestrial arctic ecosystems to climate change.TC 6, PD NOV, PY 2004, VL 33, IS 7, BP 469, EP 473, UT ISI:000225006300009

AU Callaghan, TV, Bjorn, LO, Chernov, Y, Chapin, T, Christensen, TR, Huntley, B, Ims, RA, Johansson, M, Jolly, D, Jonasson, S, Matveyeva, N, Panikov, N, Oechel, W, Shaver, GTI Uncertainties and recommendationsSO AMBIOAB An assessment of the impacts of changes in climate and UV-B radiation on Arctic terrestrial ecosystems, made within the Arctic Climate Impacts Assessment (ACIA), highlighted the profound implications of projected warming in particular for future ecosystem services, biodiversity and feedbacks to climate. However, although our current understanding of ecological processes and changes driven by climate and UV-B is strong in some geographical areas and in some disciplines, it is weak in others. Even though recently the strength of our predictions has increased dramatically with increased research effort in the Arctic and the introduction of new technologies, our current understanding is still constrained by various uncertainties. The assessment is based on a range of approaches that each have uncertainties, and on data sets that are often far from complete. Uncertainties arise from methodologies and conceptual frameworks, from unpredictable surprises, from lack of validation of models, and from the use of particular scenarios, rather than predictions, of future greenhouse gas emissions and climates. Recommendations to reduce the uncertainties are wide-ranging and relate to all disciplines within the assessment. However, a repeated theme is the critical importance of achieving an adequate spatial and long-term coverage of experiments, observations and monitoring of environmental changes and their impacts throughout the sparsely populated and remote region that is the Arctic.TC 6, PD NOV, PY 2004, VL 33, IS 7, BP 474, EP 479, UT ISI:000225006300010

Papers concerning ecosystem impacts

Flora

AU Aerts, R Cornelissen, JHC Dorrepaal, E van Logtestijn, RSP Callaghan, TVTI Effects of experimentally imposed climate scenarios on flowering phenology and flower production of subarctic bog speciesSO GLOBAL CHANGE BIOLOGYAB Climate scenarios for high-latitude areas predict not only increased summer temperatures, but also larger variation in snowfall and winter temperatures. By using open-top chambers, we experimentally manipulated both summer temperatures and winter and spring snow accumulations and temperatures independently in a blanket bog in subarctic Sweden, yielding six climate scenarios. We studied the effects of these scenarios on flowering phenology and flower production of Andromeda polifolia (woody evergreen) and Rubus chamaemorus (perennial herb) during 2 years. The second year of our study (2002) was characterized by unusually high spring and early summer temperatures. Our winter manipulations led to consistent increases in winter snow cover. As a result, average and minimum air and soil temperatures in the high snow cover treatments were higher than in the winter ambient treatments, whereas temperature fluctuations were smaller. Spring warming resulted in higher average, minimum, and maximum soil temperatures. Summer warming led to higher air and soil temperatures in mid-summer (June-July), but not in late summer (August-September). The unusually high temperatures in 2002 advanced the median flowering date by 2 weeks for both species in all treatments. Superimposed on this effect, we found that for both Andromeda and Rubus, all our climate treatments (except summer warming for Rubus) advanced flowering by 1-4 days. The total flower production of both species showed a more or less similar response: flower production in the warm year 2002 exceeded that in 2001 by far. However, in both species flower production was only stimulated by the spring-warming treatments. Our results show that the reproductive ecology of both species is very responsive to climate change but this response is very dependent on specific climate events, especially those that occur in winter and spring. This suggests that high-latitude climate change experiments should focus more on winter and spring events than has been the case so far.TC 0, PD SEP, PY 2004, VL 10, IS 9, BP 1599, EP 1609, UT ISI:000223817000015

AU Barber, VA Juday, GP Finney, BPTI Reduced growth of Alaskan white spruce in the twentieth century from temperature-induced drought stressSO NATUREAB The extension of growing season at high northern latitudes seems increasingly clear from satellite observations of vegetation extent and duration(1,2). This extension is also thought to explain the observed increase in amplitude of seasonal variations in atmospheric CO2 concentration. Increased plant respiration and photosynthesis both correlate well with increases in temperature this century and are therefore the most probable link between the vegetation and CO2 observations(3). From these observations(1,2), it has been suggested that increases in temperature have stimulated carbon uptake in high latitudes(1,2) and for the boreal forest system as a whole(4). Here we present multi-proxy tree-ring data (ring width, maximum late-wood density and carbon-isotope composition) from 20 productive stands of white spruce in the interior of Alaska. The tree-ring records show a strong and consistent relationship over the past 90 years and indicate that, in contrast with earlier predictions, radial growth has decreased with increasing temperature. Our data show that temperature-induced drought stress has disproportionately affected the most rapidly growing white spruce, suggesting that, under recent climate warming, drought may have been an important factor limiting carbon uptake in a large portion of the North

American boreal forest. If this limitation in growth due to drought stress is sustained, the future capacity of northern latitudes to sequester carbon may be less than currently expected.NR 30TC 80, PD JUN 8, PY 2000, VL 405, IS 6787, BP 668, EP 673, UT ISI:000087465800042

AU Beerling, DJ Terry, AC Mitchell, PL Callaghan, TV Gwynn-Jones, D Lee, JATI Time to chill: Effects of simulated global change on leaf ice nucleation temperatures of subarctic vegetationSO AMERICAN JOURNAL OF BOTANYAB We investigated the effects of long-term (7-yr) in situ CO2 enrichment (600 mu mol/mol) and increased exposure to UV-B radiation, the latter an important component of global change at high latitudes, on the ice nucleation temperatures of leaves of several evergreen and deciduous woody ericaceous shrubs in the subarctic (68 degrees N). Three (Vaccinium uliginosum, V. vitis-idaea, and Empetrum hermaphroditum) of the four species of shrubs studied showed significantly higher ice nucleation temperatures throughout the 1999 growing season in response to CO2 enrichment and increased exposure to UV-B radiation relative to the controls. The same species also showed a strong interactive effect when both treatments were applied together In all cases, leaves cooled to below their ice nucleation temperatures failed to survive the damage resulting from intracellular ice formation. Our results strongly suggest that future global change on a decadal time scale (atmospheric CO2 increases and polar stratospheric O-3 destruction) will lend to increased foliage damage of subarctic vegetation by severe late spring or early autumnal frosting events. Indeed, in support of our experimental findings, there is now some evidence that increases in atmospheric CO2 concentration over the past three to four decades may already have acted in this manner on high-elevation arboreal plants in the Swedish Scandes. The implications for vegetation modeling in a future "greenhouse" world and palaeoclimate estimates from high-latitude plant fossils dating to the high-CO2 environment of the Mesozoic are discussed.TC 11, PD APR, PY 2001, VL 88, IS 4, BP 628, EP 633, UT ISI:000168111200010

AU Bjerke, JW, Gwynn-Jones, D, Callaghan, TVTI Effects of enhanced UV-B radiation in the field on the concentration of phenolics and chlorophyll fluorescence in two boreal and arctic-alpine lichensSO ENVIRONMENTAL AND EXPERIMENTAL BOTANYAB Lichens constitute a prominent part of the vegetation at high latitudes and altitudes, but the effects of UV-B radiation on these symbiotic organisms are not well known. In a northern boreal site (Abisko, northern Sweden), the usnic acid-producing lichens Flavocetraria nivalis and Nephroma arcticum were exposed to enhanced UV-B radiation, corresponding to 25% ozone depletion, for two and one growing seasons, respectively. They were compared with lichens grown under ambient UV-B and harvested fresh from the field. The treated thalli of F nivalis had been transplanted from a site 24 km from the treatment site. From this source locality, untreated thalli were also harvested. Enhanced UV-B did not affect concentrations of usnic acid and the two depsides phenarctin and nephroarctin. A gradual decline of usnic acid, probably coupled to unusually long periods of dry, sunny weather, was observed both under enhanced and ambient UV-B and in untreated thalli. Photosystem II efficiency in both species was slightly reduced by enhanced UV-B. However, differences between seasons were larger than differences between treatments, which indicate that UV-B effects are minor in comparison to other climatic variables. Concentrations of UV-B-absorbing phenolics in lichens do not show a simple relationship to UV-B dose and therefore cannot be used as bioindicators of UV-B levels. (c) 2004 Elsevier B.V. All rights reserved.TC 0, PD APR, PY 2005, VL 53, IS 2, BP 139, EP 149, UT ISI:000227872100004

AU Chapin, FS, Callaghan, TV, Bergeron, Y, Fukuda, M, Johnstone, JF, Juday, G, Zimov, SA

TI Global change and the boreal forest: Thresholds, shifting states or gradual change?SO AMBIOAB Changes in boreal climate of the magnitude projected for the 21(st) century have always caused vegetation changes large enough to be societally important. However, the rates and patterns of vegetation change are difficult to predict. We review evidence suggesting that these vegetation changes may be gradual at the northern forest limit or where seed dispersal limits species distribution. However, forest composition may be quite resilient to climate change in the central portions of a species range until some threshold is surpassed. At this point, changes can be rapid and unexpected, often causing a switch to very different ecosystem types. Many of these triggers for change are amenable to management, suggesting that our choice of policies in the coming decades will substantially influence the ecological and societal consequences of current climatic change.TC 2, PD AUG, PY 2004, VL 33, IS 6, BP 361, EP 365, UT ISI:000223478300018

AU F. S. Chapin III, M. Sturm, M. C. Serreze, J. P. McFadden, J. R. Key, A. H. Lloyd, A. D. McGuire, T. S. Rupp, A. H. Lynch, J. P. Schimel, J. Beringer, W. L. Chapman, H. E. Epstein, E. S. Euskirchen, L. D. Hinzman, G. Jia, C.-L. Ping, K. D. Tape, C. D. C. Thompson, D. A. Walker, J. M. WelkTI Role of Land-Surface Changes in Arctic Summer WarmingSO SCIENCE EXPRESSAB A major challenge in predicting Earth’s future climate state is to understand feedbacks that alter greenhouse-gas forcing. Here we synthesize field data from arctic Alaska, showing that terrestrial changes in summer albedo contribute substantially to recent high-latitude warming trends. Pronounced terrestrial summer warming in arctic Alaska correlates with a lengthening of the snow-free season that has increased atmospheric heating locally by about 3 W m–2 decade–1, (similar in magnitude to the regional heating expected over multiple decades from a doubling of atmospheric CO2). Continuation of current trends in shrub and tree expansion could further amplify this atmospheric heating 2-7 times.www.sciencexpress.org / 22 September 2005 / Page 1/ 10.1126/science.1117368

AU Cooper, EJ Smith, FM Wookey, PATI Increased rainfall ameliorates the negative effect of trampling on the growth of High Arctic forage lichensSO SYMBIOSISAB Recolonisation of trampled lichen pastures in the High Arctic is dependent on the regrowth from small fragments of lichen thalli. Intact lichens have been shown to grow most rapidly during periods of sustained moisture caused by rainfall or cloudy days. Climate change models for Arctic areas predict wetter summers, milder winters and greater stochastic variability. Therefore we hypothesised that the growth of both damaged and intact Svalbard reindeer forage lichens would be increased under the future climatic scenarios. The effects of rainfall frequency, increased precipitation, and simulated cloud cover on relative growth rate (RGR) of Cetraria delisei, C. islandica and C, nivalis, from NW Svalbard were examined under controlled conditions. Low light did not depress RGR, suggesting that shading provided by increased cloud cover would not affect the lichen growth. The ability to gain mass and the RGR was lower in cut thalli than intact thalli under most watering regimes. Frequency of watering was the most important factor influencing growth, but this also interacted synergistically with quantity. Damaged thalli watered frequently grew significantly more than intact thalli watered less frequently. These results suggest that an increase in summer precipitation as predicted by climate modelling would increase the growth rate of fragmented thalli and may help to ameliorate the damage done to the Lichen thalli by reindeer trampling and grazing.NR 44, TC 5, PY 2001, VL 31, IS 1-3, BP 153, EP 171, UT ISI:000169857900012

AU Cornelissen, JHC, Callaghan, TV, Alatalo, JM, Michelsen, A, Graglia, E, Hartley, AE, Hik, DS, Hobbie, SE, Press, MC, Robinson, CH, Henry, GHR, Shaver, GR, Phoenix, GK, Jones, DG, Jonasson, S, Chapin, FS, Molau, U, Neill, C, Lee, JA, Melillo, JM, Sveinbjornsson, B, Aerts, RTI Global change and arctic ecosystems: is lichen decline a function of increases in vascular plant biomass?SO JOURNAL OF ECOLOGYAB 1 Macrolichens are important for the functioning and biodiversity of cold northern ecosystems and their reindeer-based cultures and economics. 2 We hypothesized that, in climatically milder parts of the Arctic, where ecosystems have relatively dense plant canopies, climate warming and/or increased nutrient availability leads to decline in macrolichen abundance as a function of increased abundance of vascular plants. In more open high-arctic or arctic-alpine plant communities such a relationship should be absent. To test this, we synthesized cross-continental arctic vegetation data from ecosystem manipulation experiments simulating mostly warming and increased nutrient availability, and compared these with similar data from natural environmental gradients. 3 Regressions between abundance or biomass of macrolichens and vascular plants were consistently negative across the subarctic and mid-arctic experimental studies. Such a pattern did not emerge in the coldest high-arctic or arctic-alpine sites. The slopes of the negative regressions increased across 10 sites as the climate became milder (as indicated by a simple climatic index) or the vegetation denser (greater site above-ground biomass). 4 Seven natural vegetation gradients in the lower-altitude sub- and mid-arctic zone confirmed the patterns seen in the experimental studies, showing consistent negative relationships between abundance of macrolichens and vascular plants. 5 We conclude that the data supported the hypothesis. Macrolichens in climatically milder arctic ecosystems may decline if and where global changes cause vascular plants to increase in abundance. 6 However, a refining of our findings is needed, for instance by integrating other abiotic and biotic effects such as reindeer grazing feedback on the balance between vascular plants and lichens.TC 23, PD DEC, PY 2001, VL 89, IS 6, BP 984, EP 994, UT ISI:000172926100007

AU Dorrepaal, E, Aerts, R, Cornelissen, JHC, Callaghan, TV, van Logtestijn, RSPTI Summer warming and increased winter snow cover affect Sphagnum fuscum growth, structure and production in a sub-arctic bogSO GLOBAL CHANGE BIOLOGYAB Sphagnum mosses form a major component of northern peatlands, which are expected to experience substantially higher increases in temperature and winter precipitation than the global average. Sphagnum may play an important role in the responses of the global carbon cycle to climate change. We investigated the responses of summer length growth, carpet structure and production in Sphagnum fuscum to experimentally induced changes in climate in a sub-arctic bog. Thereto, we used open-top chambers (OTCs) to create six climate scenarios including changes in summer temperatures, and changes in winter snow cover and spring temperatures. In winter, the OTCs doubled the snow thickness, resulting in 0.5-2.8degreesC higher average air temperatures. Spring air temperatures in OTCs increased by 1.0degreesC. Summer warming had a maximum effect of 0.9degreesC, while vapor pressure deficit was not affected. The climate manipulations had strong effects on S. fuscum. Summer warming enhanced the length increment by 42-62%, whereas bulk density decreased. This resulted in a trend (P<0.10) of enhanced biomass production. Winter snow addition enhanced dry matter production by 33%, despite the fact that the length growth and bulk density did not change significantly. The addition of spring warming to snow addition alone did not significantly enhance this effect, but we may have missed part of the early spring growth. There were no interactions between the manipulations in summer and those in winter/spring, indicating that the effects were additive. Summer warming

may in the long term negatively affect productivity through the adverse effects of changes in Sphagnum structure on moisture holding and transporting capacity. Moreover, the strong length growth enhancement may affect interactions with other mosses and vascular plants. Because winter snow addition enhanced the production of S. fuscum without affecting its structure, it may increase the carbon balance of northern peatlands.TC 1, PD JAN, PY 2004, VL 10, IS 1, BP 93, EP 104, UT ISI:000187848200009

AU Frey, KE Smith, LCTI Amplified carbon release from vast West Siberian peatlands by 2100SO GEOPHYSICAL RESEARCH LETTERSAB Extensive new data from previously unstudied Siberian streams and rivers suggest that mobilization of currently frozen, high-latitude soil carbon is likely over the next century in response to predicted Arctic warming. We present dissolved organic carbon (DOC) measurements from ninety-six watersheds in West Siberia, a region that contains the world's largest stores of peat carbon, exports massive volumes of freshwater and DOC to the Arctic Ocean, and is warming faster than the Arctic as a whole. The sample sites span &SIM; 10(6) km(2) over a large climatic gradient ( &SIM; 55 - 68 &DEG; N), providing data on a much broader spatial scale than previous studies and for the first time explicitly examining stream DOC in permafrost peatland environments. Our results show that cold, permafrost-influenced watersheds release little DOC to streams, regardless of the extent of peatland cover. However, we find considerably higher concentrations in warm, permafrost-free watersheds, rising sharply as a function of peatland cover. The two regimes are demarcated by the position of the -2&DEG; C mean annual air temperature (MAAT) isotherm, which is also approximately coincident with the permafrost limit. Climate model simulations for the next century predict near-doubling of West Siberian land surface areas with a MAAT warmer than -2&DEG; C, suggesting up to &SIM; 700% increases in stream DOC concentrations and &SIM; 2.7 - 4.3 Tg yr(-1) (&SIM; 29 - 46%) increases in DOC flux to the Arctic Ocean.NR 28, TC 1, PD MAY 5, PY 2005, VL 32, IS 9, AR L09401, UT ISI:000229145100002

AU Johnson, D, Campbell, CD, Lee, JA, Callaghan, TV, Gwynn-Jones, DTI Arctic microorganisms respond more to elevated UV-B radiation than CO2SO NATUREAB Surface ultraviolet-B radiation and atmospheric CO2 concentrations have increased as a result of ozone depletion and burning of fossil fuels(1,2). The effects are likely to be most apparent in polar regions(3) where ozone holes have developed and ecosystems are particularly sensitive to disturbance(4). Polar plant communities are dependent on nutrient cycling by soil microorganisms, which represent a significant and highly labile portion of soil carbon (C) and nitrogen (N). It was thought(5) that the soil microbial biomass was unlikely to be affected by exposure of their associated plant communities to increased UV-B. In contrast, increasing atmospheric CO2 concentrations were thought to have a strong effect as a result of greater below-ground C allocation(6). In addition, there is a growing belief that ozone depletion is of only minor environmental concern because the impacts of UV-B radiation on plant communities are often very subtle(7). Here we show that 5 years of exposure of a subarctic heath to enhanced UV-B radiation both alone and in combination with elevated CO2 resulted in significant changes in the C:N ratio and in the bacterial community structure of the soil microbial biomass.TC 27, PD MAR 7, PY 2002, VL 416, IS 6876, BP 82, EP 83, UT ISI:000174211600042

AU Phoenix, GK, Gwynn-Jones, D, Callaghan, TV, Sleep, D, Lee, JATI Effects of global change on a sub-Arctic heath: effects of enhanced UV-B radiation and increased summer precipitationSO JOURNAL OF ECOLOGY

AB 1 The responses of sub-Arctic heathland vegetation to enhanced UV-B radiation and increased summer precipitation over 7 years were investigated in a field experiment in northern Sweden. 2 Growth, phenology and reproduction of the dominant dwarf shrubs Vaccinium myrtillus, V. uliginosum, V. vitis-idaea and Empetrum hermaphroditum were studied after 5-7 years of manipulation and retrospective analyses were used to assess growth responses in earlier years. Leaf tissue N and P and C-13 natural abundances were determined for V. myrtillus and E. hermaphroditum. Growth responses were also assessed for the moss Hylocomium splendens. 3 The deciduous V. myrtillus showed reduced growth, increased leaf thickness and increased flowering and berry production under enhanced UV-B in some years. V. uliginosum, V. vitis-idaea, E. hermaphroditum and H. splendens were, in general, tolerant of UV-B. 4 Increased precipitation affected growth only in the evergreen species: stem length and branching were sometimes stimulated in E. hermaphroditum, whereas V. vitis-idaea showed reduced branching. 5 Precipitation also increased leaf thickness in V. uliginosum and reduced flowering and berry production in V. myrtillus. 6 In the interactions that occurred between enhanced UV-B radiation and increased summer precipitation, combining the two treatments often negated any effect that either may have had separately. The effect of concurrent increases on this ecosystem is therefore likely to be much less than if either occurred singly. 7 Enhanced UV-B and increased summer precipitation appeared not to effect dwarf shrub abundances during the first 5 years of the experiment, suggesting that overall this heath may be more tolerant of these environmental changes than previously thought.TC 24, PD APR, PY 2001, VL 89, IS 2, BP 256, EP 267, UT ISI:000168692200011

AU Simpson, JJ Hufford, GL Fleming, MD Berg, JS Ashton, JBTI Long-term climate patterns in Alaskan surface temperature and precipitation and their biological consequencesSO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSINGAB Mean monthly climate maps of Alaskan surface temperature and precipitation produced by the parameter-elevation regression on independent slopes model (PRISM) were analyzed. Alaska is divided into interior and coastal zones with consistent but different climatic variability separated by a transition region; it has maximum interannual variability but low long-term mean variability. Pacific decadal oscillation (PDO)- and El Nino southern oscillation (ENSO)-type events influence Alaska surface temperatures weakly (1-2 degreesC) statewide. PDO has a stronger influence than ENSO on precipitation but its influence is largely localized to coastal central Alaska. The strongest influence of Arctic oscillation (AO) occurs in northern and interior Alaskan precipitation. Four major ecosystems are defined. A major eco-transition zone occurs between the interior boreal forest and the coastal rainforest. Variability in insolation, surface temperature, precipitation, continentality, and seasonal changes in storm track direction explain the mapped ecosystems. Lack of westward expansion of the interior boreal forest into the western shrub tundra is influenced by the coastal marine boundary layer (enhanced cloud cover, reduced insolation, cooler surface and soil temperatures). In this context, the marine boundary layer acts in an analogous fashion to the orographic features which form the natural boundaries of other Alaskan ecosystems. Variability in precipitation may play a secondary role.

AU Skre, O, Baxter, R, Crawford, RMM, Callaghan, TV, Fedorkov, ATI How will the tundra-taiga interface respond to climate change?SO AMBIOAB The intuitive and logical answer to the question of how the tundra-taiga interface will react to global warming is that it should move north and this is mirrored by many models of potential treeline migration. Northward movement may be the eventual outcome if climatic warming persists over centuries or millennia. However, closer examination of the tundra-taiga interface across its circumpolar extent reveals a more complex situation. The regional climatic history of

the tundra-taiga interface is highly varied, and consequently it is to be expected that the forest tundra boundary zone will respond differently to climate change depending on local variations in climate, evolutionary history, soil development, and hydrology. Investigations reveal considerable stability at present in the position of the treeline and while there may be a long-term advance northwards there are oceanic regions where climatic warming may result in a retreat southwards due to increased bog development. Reinforcing this trend is an increasing human impact, particularly in the forest tundra of Russia, which forces the limit of the forested areas southwards. Local variations will therefore require continued observation and research, as they will be of considerable importance economically as well as for ecology and conservation.TC 1, PD AUG, PY 2002, SI Sp. Iss. 12, BP 37, EP 46, UT ISI:000178086300006

AU Sturm, M Schimel, J Michaelson, G Welker, JM Oberbauer, SF Liston, GE Fahnestock, J Romanovsky, VETI Winter biological processes could help convert arctic tundra to shrublandSO BIOSCIENCEAB In arctic Alaska, air temperatures have warmed 0.5 degrees Celsius (degreesC) per decade for the past 30 years, winter. Over the same period, shrub abundance has increased, perhaps a harbinger of a conversion of tundra to shrubland. Evidence suggests that winter biological processes are contributing to this conversion through a positive feedback that involves the snow-holding capacity of shrubs, the insulating properties of snow, a soil layer that has a high water content because it overlies nearly impermeable permafrost, and hardy microbes that can maintain metabolic activity at temperatures of -6degreesC or lower. Increasing shrub abundance leads to deeper snow, which promotes higher winter soil temperatures, greater microbial activity and more plant-available nitrogen. High levels of soil nitrogen favor shrub growth the follow- summer. With climate models predicting continued warming, large areas of tundra could become converted to shrubland, with winter processes like those described here possibly playing a critical role.NR 66, TC 5, PD JAN, PY 2005, VL 55, IS 1, BP 17, EP 26, UT ISI:000226343000009

AU Timoney, KPTI The changing disturbance regime of the boreal forest of the Canadian Prairie ProvincesSO FORESTRY CHRONICLEAB The subhumid boreal forest of western Canada is different today from what it was 25 years ago. Before the 1950s, the main human impacts on this forest were agricultural expansion, escaped settlement fires, and high-grade logging. The latter half of the 20(th) Century saw increased human stresses placed on the ecosystems, against a background of insect outbreaks and high forest fire activity. In the Prairie provinces, current annual area burned is greater and more variable than it was in the 1970s. Over the past 25 years, the area disturbed by insects (primarily forest tent caterpillar) and disease has declined, but both the area and timber volume logged have risen. The boreal forest (particularly its southern half) is being converted to a fragmented landscape dominated by young aspen, shrub, grass, plantations, exotic species, industrial infrastructure, and agricultural fields. The current disturbance level has increased to the point that forest land and volume losses now exceed forest accruals in some regions; average forest age and biomass have been declining since about 1970. Relative to past decades, the present subhumid boreal forest region of Canada is warmer, and more fragmented and dissected; it supports less old growth, less old white spruce, and more young aspen and recently disturbed areas; it has simplified and truncated age-class structures; and it has a greater prevalence of non-native plants. Future stresses may include in situ tar sands development, groundwater depletion or degradation, and water diversions. Should present trends continue, declining forest productivity and predictability, and spread of exotic species are likely, as is replacement of coniferous forest by deciduous forest in some regions. Stressed aquatic systems may undergo major changes in biotic

composition, productivity, and physical characteristics. Without a rapid decrease in the rate of disturbances, the establishment of a more complete protected areas network, and the adoption of ecosystem-centred management, the subhumid boreal ecosystem will continue to be degraded.TC 0, PD MAY-JUN, PY 2003, VL 79, IS 3, BP 502, EP 516, UT ISI:000184445600036

PT JAU Wilmking, M D'Arrigo, R Jacoby, GC Juday, GPTI Increased temperature sensitivity and divergent growth trends in circumpolar boreal forestsSO GEOPHYSICAL RESEARCH LETTERSAB Tree rings have been used to both reconstruct past climate, and to estimate and project carbon uptake of forest ecosystems. Here we show that large groups of trees of the dominant tree species within widely-distributed circumpolar forest sites show opposing growth trends during recent warming. These opposing growth trends are present at a sub-chronology level and, if averaged into chronologies, may have contributed to the widely reported overall decreased temperature sensitivity of high-latitude chronologies over recent decades. Unlike previous studies, we find that temperature sensitivity has actually increased for most individual trees at these sites. This recent, widespread divergence in growth response seems unique over the past three centuries, and may relate to different microsite responses of individual trees to temperature-induced drought stress or other factors. This divergence needs to be taken into account in dendroclimatic reconstructions, estimations of global warming impacts, and carbon uptake projections.NR 18, TC 0, PD AUG 13, PY 2005, VL 32, IS 15, AR L15715, UT ISI:000231380800004

AU Wilmking, M Juday, GP Barber, VA Zald, HSJTI Recent climate warming forces contrasting growth responses of white spruce at treeline in Alaska through temperature thresholdsSO GLOBAL CHANGE BIOLOGYAB Northern and high-latitude alpine treelines are generally thought to be limited by available warmth. Most studies of tree-growth-climate interaction at treeline as well as climate reconstructions using dendrochronology report positive growth response of treeline trees to warmer temperatures. However, population-wide responses of treeline trees to climate remain largely unexamined. We systematically sampled 1558 white spruce at 13 treeline sites in the Brooks Range and Alaska Range. Our findings of both positive and negative growth responses to climate warming at treeline challenge the widespread assumption that arctic treeline trees grow better with warming climate. High mean temperatures in July decreased the growth of 40% of white spruce at treeline areas in Alaska, whereas warm springs enhance growth of additional 36% of trees and 24% show no significant correlation with climate. Even though these opposing growth responses are present in all sampled sites, their relative proportion varies between sites and there is no overall clear relationship between growth response and landscape position within a site. Growth increases and decreases appear in our sample above specific temperature index values (temperature thresholds), which occurred more frequently in the late 20th century. Contrary to previous findings, temperature explained more variability in radial growth after 1950. Without accounting for these opposite responses and temperature thresholds, climate reconstructions based on ring width will miscalibrate past climate, and biogeochemical and dynamic vegetation models will overestimate carbon uptake and treeline advance under future warming scenarios.NR 39, TC 3, PD OCT, PY 2004, VL 10, IS 10, BP 1724, EP 1736, UT ISI:000224297500009

Fauna

AU Coulson, SJ Hodkinson, ID Webb, NR Mikkola, K Harrison, JA Pedgley, DETI Aerial colonization of high Arctic islands by invertebrates: the diamondback moth Plutella xylostella (Lepidoptera : Yponomeutidae) as a potential indicator speciesSO DIVERSITY AND DISTRIBUTIONSAB The restricted animal communities of the high Arctic islands are due, in part, to extreme geographical isolation. Migration via wind currents is one mechanism by which invasion of new species may occur. Here, we describe immigration of the non-resident migratory moth, Plutella xylostella, into Svalbard during 2000. This was associated with a warm southeasterly air mass that crossed from W. Russia: moths appear to have covered the 800 km to Svalbard in under 48 h, flying at an altitude between 500 and 1500 m. These events thus provide a case study for wind-dispersed movements of invertebrates to high Arctic regions. Climate change scenarios predict increased frequency of such air masses and also of the warm dry weather associated with increased aerial insect transport. The general factors determining successful colonization of the high Arctic by wind-dispersed animals are discussed, using P. xylostella as a model species whose important life history and physiological attributes are well known.NR 33, TC 5, PD NOV, PY 2002, VL 8, IS 6, BP 327, EP 334, UT ISI:000178798200003

AU Finstad, AG Forseth, T Faenstad, TF Ugedal, OTI The importance of ice cover for energy turnover in juvenile Atlantic salmonSO JOURNAL OF ANIMAL ECOLOGYAB 1. Under benign laboratory tank conditions we compared food consumption and metabolism of Atlantic salmon (Salmo salar) juveniles exposed to simulated ice cover (darkness) with fish in natural short, 6 h light, day length (without ice). Three different populations along an ice-cover gradient were tested (59degreesN-70degreesN). 2. Resting metabolism was on average 30% lower under simulated ice cover (6.6 J g(-1) day(-1)) than under natural day length (9.4 J g(-1) day(-1)), and the response was similar for all populations. Northern salmon grew equally well in dark and light conditions, whereas the southern grew significantly poorer in the dark. Fish from all populations fed more under natural day length than in the dark and the northern population had higher consumption than the southern. The relative high growth of fish from the northern population in the dark compared to the southern populations was due partly to higher consumption and partly to higher growth efficiency. Fish from the southern populations had negative growth efficiency in the dark. 3. We also studied the importance of ice cover under more hostile conditions in stream channels using the northern population only. Juveniles held in channels with simulated ice cover lost less energy (20 J g(-1) day(-1)) than those held in channels with transparent cover (26 J g(-1) day(-1)). This difference in energy loss was due partly (50%) to higher food consumption under simulated ice (4.5 and 1.6 J g(-1), respectively) and partly (30%) to light-induced differences in resting metabolic rate. 4. In conclusion, both experiments showed lower metabolic costs in darkness under simulated ice cover than without ice. Under benign laboratory conditions the response to light (ice cover) varied among populations and only the northern population were able to attain positive growth in the dark. Under semi-natural conditions the lack of ice cover induced strong negative effects on the energy budget. Because energetic deficiencies are assumed to be an important cause of winter mortality, our study indicates that ice break-ups or removal following climatic change may affect winter survival significantly, particularly in northern populations.TC 0, PD SEP, PY 2004, VL 73, IS 5, BP 959, EP 966, UT ISI:000223375900014

AU Schindler, DE Rogers, DE Scheuerell, MD Abrey, CATI Effects of changing climate on zooplankton and juvenile sockeye salmon growth in southwestern Alaska

SO ECOLOGYAB Detecting and forecasting the effects of changing climate on natural and exploited populations represent a major challenge to ecologists and resource managers. These efforts are complicated by underlying density-dependent processes and the differential responses of predators and their prey to changing climate. We explored the effects of density-dependence and changing climate on growth of juvenile sockeye salmon and the densities of their zooplankton prey in the Wood River system of southwestern Alaska. We fit dynamic time-series models to data collected between 1962 and 2002 describing growth of juvenile sockeye, timing of spring ice breakup, and summer zooplankton densities. The timing of spring breakup has moved about seven days earlier now than it was in the early 1960s. Our analyses suggest that most of this shift has been a response to the warm phase of the Pacific Decadal Oscillation that persisted from the mid-1970s to the late 1990s. This progression toward earlier spring breakup dates was associated with warmer summer water temperatures and increased zooplankton (especially Daphnia) densities, which translated into increased sockeye growth during their first year of life. The number of spawning adults that produced each year class of sockeye had a strong negative effect on juvenile sockeye growth rates, so that the size of the density-dependent effect was, on average, twice as large as the effect of spring breakup date. These results highlight the complexity of ecological responses to changing climate and suggest that climate warming may enhance growing conditions for juvenile salmonids in large lakes of Alaska.TC 1, PD JAN, PY 2005, VL 86, IS 1, BP 198, EP 209, UT ISI:000226791700020

Papers including societal impacts

AU Brunner, RD Lynch, AH Pardikes, JC Cassano, EN Lestak, LR Vogel, JMTI An Arctic disaster and its policy implicationsSO ARCTICAB The purpose of the research reported here is to help the community in Barrow, Alaska, clarify its vulnerability to extreme weather events, and devise better-informed policies for reducing that vulnerability and adapting to climate variability and change. We examine the worst disaster on record there-a storm that struck on 3 October 1963-from different disciplinary perspectives and in the context of other severe storms. The major policy responses to date have been a beach nourishment program, a feasibility study of additional means of erosion control, and an emergency management plan. Additional possible responses have been identified in the community's cumulative experience of these storms, but have not yet been fully explored or implemented. Meanwhile, given inherent uncertainties, it is clear that sound policies will allow for corrective action if and when expectations based on the best available knowledge and information turn out to be mistaken. It is also clear that the people of Barrow are in the best position to understand the evolving situation and to decide what to do about it.NR 46, TC 0, PD DEC, PY 2004, VL 57, IS 4, BP 336, EP 346, UT ISI:000225795300003

AU Chapin, FS Peterson, G, Berkes, F, Callaghan, TV, Angelstam, P, Apps, M, Beier, C, Bergeron, Y, Crepin, AS, Danell, K, Elmqvist, T, Folke, C, Forbes, B, Fresco, N, Juday, G, Niemela, J, Shvidenko, A, Whiteman, GTI Resilience and vulnerability of northern regions to social and environmental changeSO AMBIOAB The arctic tundra and boreal forest were once considered the last frontiers on earth because of their vast expanses remote from agricultural land-use change and industrial development. These regions are now, however, experiencing environmental and social changes that are as rapid as those occurring anywhere on earth. This paper summarizes the role of northern regions in the

global system and provides a blueprint for assessing the factors that govern their sensitivity to social and environmental change.TC 3, PD AUG, PY 2004, VL 33, IS 6, BP 344, EP 349, UT ISI:000223478300015

AU Grunzweig, JM Sparrow, SD Yakir, D Chapin, FSTI Impact of agricultural land-use change on carbon storage in boreal AlaskaSO GLOBAL CHANGE BIOLOGYAB Climate warming is most pronounced at high latitudes, which could result in the intensification of the extensively cultivated areas in the boreal zone and could further enhance rates of forest clearing in the coming decades. Using paired forest-field sampling and a chronosequence approach, we investigated the effect of conversion of boreal forest to agriculture on carbon (C) and nitrogen (N) dynamics in interior Alaska. Chronosequences showed large soil C losses during the first two decades following deforestation, with mean C stocks in agricultural soils being 44% or 8.3 kg m(-2) lower than C stocks in original forest soils. This suggests that soil C losses from land-use change in the boreal region may be greater than those in other biomes. Analyses of changes in stable C isotopes and in quality of soil organic matter showed that organic C was lost from soils by combustion of cleared forest material, decomposition of organic matter and possibly erosion. Chronosequences indicated an increase in C storage during later decades after forest clearing, with 60-year-old grassland showing net ecosystem C gain of 2.1 kg m(-2) over the original forest. This increase in C stock resulted probably from a combination of large C inputs from belowground biomass and low C losses due to a small original forest soil C stock and low tillage frequency. Reductions in soil N stocks caused by land-use change were smaller than reductions in C stocks (34% or 0.31 kg m(-2)), resulting in lower C/N ratios in field compared with forest mineral soils, despite the occasional incorporation of high-C forest-floor material into field soils. Carbon mineralization per unit of mineralized N was considerably higher in forests than in fields, which could indicate that decomposition rates are more sensitive in forest soils than in field soils to inorganic N addition (e.g. by increased N deposition from the atmosphere). If forest conversion to agriculture becomes more widespread in the boreal region, the resulting C losses (51% or 11.2 kg m(-2) at the ecosystem level in this study) will induce a positive feedback to climatic warming and additional land-use change. However, by selecting relatively C-poor soils and by implementing management practices that preserve C, losses of C from soils can be reduced.NR 91, TC 0, PD APR, PY 2004, VL 10, IS 4, BP 452, EP 472, UT ISI:000220548800006

AU Humlum, O Instanes, A Sollid, JLTI Permafrost in Svalbard: a review of research history, climatic background and engineering challengesSO POLAR RESEARCHAB This paper reviews permafrost in High Arctic Svalbard, including past and current research, climatic background, how permafrost is affected by climatic change, typical permafrost landforms and how changes in Svalbard permafrost may impact natural and human systems. Information on active layer dynamics, permafrost and ground ice characteristics and selected periglacial features is summarized from the recent literature and from unpublished data by the authors. Permafrost thickness ranges from less than 100 m near the coasts to more than 500 m in the highlands. Ground ice is present as rock glaciers, as ice-cored moraines, buried glacial ice, and in pingos and ice wedges in major valleys. Engineering problems of thaw-settlement and frost-heave are described, and the implications for road design and construction in Svalbard permafrost areas are discussed.NR 203, TC 4, PY 2003, VL 22, IS 2, BP 191, EP 215, UT ISI:000187618900006

AU Lynch, AH Curry, JA Brunner, RD Maslanik, JA

TI Toward an integrated assessment of the impacts of extreme wind events on Barrow, AlaskaSO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETYAB Warming of the arctic climate is having a substantial impact on the Alaskan North Slope coastal region. The warming is associated with increasing amounts of open water in the arctic seas, rising sea level, and thawing permafrost. Coastal geography and increasing development along the coastline are contributing to increased vulnerability of infrastructure, utilities, and supplies of food and gasoline to storms, flooding, and coastal erosion. Secondary impacts of coastal flooding may include harm to animals and their land or sea habitats, if pollutants are released. Further, Inupiat subsistence harvesting of marine sources of food, offshore resource extraction, and marine transportation may be affected. This paper describes a project to understand, support, and enhance the local decision-making process on the North Slope of Alaska on socioeconomic issues that are influenced by warming climate variability, and extreme weather events.NR 35, TC 2, PD FEB, PY 2004, VL 85, IS 2, BP 209, EP +, UT ISI:000220121800016

AU Macdonald, RW Harner, T Fyfe, JTI Recent climate change in the Arctic and its impact on contaminant pathways and interpretation of temporal trend dataSO SCIENCE OF THE TOTAL ENVIRONMENTAB The Arctic has undergone dramatic change during the past decade. The observed changes include atmospheric sea-level pressure, wind fields, sea-ice drift, ice cover, length of melt season, change in precipitation patterns, change in hydrology and change in ocean currents and watermass distribution. It is likely that these primary changes have altered the carbon cycle and biological systems, but the difficulty of observing these together with sporadic, incomplete time series makes it difficult to evaluate what the changes have been. Because contaminants enter global systems and transport through air and water, the changes listed above will clearly alter contaminant pathways. Here, we review what is known about recent changes using the Arctic Oscillation as a proxy to help us understand the forms under which global change will be manifest in the Arctic. For Pb, Cd and Zn, the Arctic is likely to become a more effective trap because precipitation is likely to increase. In the case of Cd, the natural cycle in the ocean appears to have a much greater potential to alter exposure than do human releases of this metal. Mercury has an especially complex cycle in the Arctic including a unique scavenging process (mercury depletion events), biomagnifying foodwebs, and chemical transformations such as methylation. The observation that mercury seems to be increasing in a number of aquatic species whereas atmospheric gaseous mercury shows little sign of change suggests that factors related to change in the physical system (ice cover, permafrost degradation, organic carbon cycling) may be more important than human activities. Organochlorine contaminants offer a surprising array of possibilities for changed pathways. To change in precipitation patterns can be added change in ice cover (air-water exchange), change in food webs either from the top down or from the bottom up (biomagnification), change in the organic carbon cycle and change in diets. Perhaps the most interesting possibility, presently difficult to predict, is combination of immune suppression together with expanding ranges of disease vectors. Finally, biotransport through migratory species is exceptionally vulnerable to changes in migration strength or in migration pathway-in the Arctic, change in the distribution of ice and temperature may already have caused such changes. Hydrocarbons, which tend to impact surfaces, will be mostly affected by change in the ice climate (distribution and drift tracks). Perhaps the most dramatic changes will occur because our view of the Arctic Ocean will change as it becomes more amenable to transport, tourism and mineral exploration on the shelves. Radionuclides have tended not to produce a radiological problem in the Arctic; nevertheless one pathway, the ice, remains a risk because it can accrue, concentrate and transport radio-contaminated sediments. This pathway is sensitive to where ice is produced, what the transport pathways of ice are, and where ice is finally melted-all strong

candidates for change during the coming century. The changes that have already occurred in the Arctic and those that are projected to occur have an effect on contaminant time series including direct measurements (air, water, biota) or proxies (sediment cores, ice cores, archive material). Although these 'system' changes can alter the flux and concentrations at given sites in a number of obvious ways, they have been all but ignored in the interpretation of such time series. To understand properly what trends mean, especially in complex 'recorders' such as seals, walrus and polar bears, demands a more thorough approach to time series by collecting data in a number of media coherently. Presently, a major reservoir for contaminants and the one most directly connected to biological uptake in species at greatest risk-the ocean-practically lacks such time series. Crown Copyright &COPY; 2004 Published by Elsevier B.V All rights reserved.TC 0, PD APR 15, PY 2005, VL 342, IS 1-3, SI Sp. Iss. SI, BP 5, EP 86, UT ISI:000229599600002

AU Turner, BL Matson, PA McCarthy, JJ Corell, RW Christensen, L Eckley, N Hovelsrud-Broda, GK Kasperson, JX Kasperson, RE Luers, A Martello, ML Mathiesen, S Naylor, R Polsky, C Pulsipher, A Schiller, A Selin, H Tyler, NTI Illustrating the coupled human-environment system for vulnerability analysis: Three case studiesSO PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICAAB The vulnerability framework of the Research and Assessment Systems for Sustainability Program explicitly recognizes the coupled human-environment system and accounts for interactions in the coupling affecting the system's responses to hazards and its vulnerability. This paper illustrates the usefulness of the vulnerability framework through three case studies: the tropical southern Yucatan, the and Yaqui Valley of northwest Mexico, and the pan-Arctic. Together, these examples illustrate the role of external forces in reshaping the systems in question and their vulnerability to environmental hazards, as well as the different capacities of stakeholders, based on their access to social and biophysical capital, to respond to the changes and hazards. The framework proves useful in directing attention to the interacting parts of the coupled system and helps identify gaps in information and understanding relevant to reducing vulnerability in the systems as a whole.NR 41,TC 12, PD JUL 8, PY 2003, VL 100, IS 14, BP 8080, EP 8085, UT ISI:000184222500010