Average annual temperature increase from 1971-2000. Ring-width chronologies from the West Coast and South Central/South East climate zones are (1) Seward and (2) Rock Tor. The sites in the Lake Clark area, (3), are located near the King Salmon meteorological station, which has experienced considerable warming.

A New Dendroclimatic Tree Ring Network from Lake Clark National Park and Preserve, AlaskaWill Driscoll and Greg Wiles, Department of Geology, the College of Wooster, Wooster, OH, 44691; wdriscoll@wooster.edu

Four white spruce (Picea glauca [Moench] Voss) tree-ring sites were collected near elevational treeline along a 60 km north-south transect in Lake Clark National Park and Preserve, Alaska. The collections are well-replicated (more than 50 cores each) with three sites exceeding 300 years in age. Ring-width series and latewood density series will contribute to defining the climate variability of the western flank of the Chigmit Mountains on the Alaska Peninsula where the Alaska Range meet the Aleutians. This climatically transitional area between maritime and continental regimes includes the headwaters of some of the most productive salmon fisheries in Alaska. Dendroclimatic reconstructions of past temperatures can then be compared with other efforts to reconstruct past salmon populations from spawning lakes in the region to identify the role of climate variability on biological systems.

Monthly climate records from King Salmon, 150 km to the south, with tree growth to identify the climate response of the trees. Preliminary results suggest that forests in the region continue to record warming, whereas other records from Alaska shows dramatic decreases in forest growth as new stresses (i.e., drying) associated with climate change impact growth. In addition to identifying climate variability over the last several hundred years along the western flank of the Chigmit Mountains, tree-ring series will be compared with other meteorological records (Homer, Kodiak) as well regional climatic indices to contribute to modeling North Pacific climate variability.

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Climate zones of Alaska. Lake Clark chronologies (3) were taken from the transitional maritime/continental region between the West Coast and South Central/Southeast. Chronologies from the Lake Clark National Park and Preserve are compared to other chronologies from the Seward Peninsula (1) and maritime Prince William Sound (Rock Tor, 2).

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Methods. Standard dendrochronological methods were used to build ring-width chronologies (Fritts, 1976; Stokes and Smiley, 1968). Cores were taken from generally well-spaced white spruce (Picea glauca [Moench] Voss) trees at four treeline sites in the Lake Clark National Park and Preserve. Forty cores from 30 trees at the lower Twin Lake site and twenty cores from 15 trees at the middle Lake Telaquana site make up the data set presented here.

Looking East at the Chigmit Mountains, Lower Twin Lake, Lake Clark National Park and Preserve, Alaska. Note the well-spaced white spruce trees near the elevational treeline.

Coring a white spruce tree at Fish Trap Lake.

Average monthly precipitation at King Salmon, Alaska

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Correlations between indices and temperature/precipitation at Telaquana Lake

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Average monthly temperature at King Salmon from 1947 to 2000.

Average temperature and precipitation per month at King Salmon, AK

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Average monthly precipitation at King Salmon from 1947 to 2000.

Correlation of monthly temperature and precipitation averages with tree growth. Precipitation appears to have a minimal impact, with an almost even distribution of positive and negative correlations of varying degrees. Temperature seems to be a much more powerful and consistent forcing factor.The common period between the two data sets is 55 years.

The Twin Lake chronology shows strong correlations with temperature in the months of April through July. This suggests that the Twin Lake chronology may serve as a proxy record for past late spring/early summer temperatures. The common period is 55 years.

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Graphical comparison of ring widths for Twin Lake (green) and June temperatures (red) at King Salmon. The historical June temperatures drop off relative to ring growth in the early- to mid-1990s. Tree growth, while largely a function of temperature, appears to be compounded by some other factor or factors.

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Twin Lake and Seward Ring Width Chronologies

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Twin Lake and Rock Tor Ring Width Chronologies

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Here, we compare the Twin Lake chronology (green, transitional climate system) to others from Seward Peninsula (red, a maritime climate system) and Rock Tor, near Valdez (brown, a continental climate system) in order to better understand the accelerated growth over the past decade. Note the final decade in both comparisons; the Twin Lake trees experienced levels of growth that were greatly acceleration relative to the other two sites.

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Ring-width chronology for Twin Lake. Four hundred years of tree growth based on living trees and subfossil logs shows a strong increase in growth over the past few decades. This chronology is well-replicated back to AD 1700. Ring-width indices are calculated based on the removal of negative exponential growth functions.

Ring-width chronology for Lake Telaquana. Several characteristics of the Twin Lake chronology are readily visible in the Lake Telaquana chronology. The 1810s, again, are abnormally cold, although the warm 1950s appear more subdued in this chronology. Low frequency warming since 1900 is immediately obvious, but the accelerated growth of the 1990s, while clearly present, is less dramatic than in the Twin Lake chronology.

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Twin Lake and Lake Telaquana Ring Width Chronologies

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The Twin Lake (green) and Lake Telaquana (red) chronologies. The two chronologies are remarkably similar and record both the gradual warming of the 1900s and the more dramatic warming of the 1990s. Growth acceleration, then, is not unique to one site and may be characteristic of the Lake Clark region. This suggests that trees continue to record elevated temperatures, whereas at many other sites in Alaska ring-widths are showing decreases in growth over recent decades.

Discussion. The Twin Lake chronology appears to be sensitive to late spring/early summer temperatures. The major features of the chronology are replicated in the chronology from the neighboring Lake Telaquana, suggesting that the dominant forces were not specific to one site. However, the warming of the 1980s/1990s, while present to some extent in other chronologies across Alaska, appears to be much greater in the Lake Clark region. Two more ring-width sites from Fish Trap Lake and Portage Lake are now being processed, both of which record over three hundred years. These chronologies will add to our knowledge of the past climate in the Lake Clark region and together with these data will lead to a temperature reconstruction for the past several hundred years.

Tree Rings and ClimateTrees integrate information

About soil temperature as well as Surface air temperature. We calibrate The ring-width data using observed Temperature data.

One of the Alaska Peninsula’s volcanoes

View from Portage Lake looking east at the Chigmit Mountains

Abstract

Source: Alaska Climate Center

Source: Alaska Climate Center

Ackowledgements: We thank R. D’Arrigo for the Seward Peninsula data and R. Wilson for processing the Rock Tor site in Prince William Sound. N. Young helped with field sampling and A. Horst with the tree-ring processing. P. Spencer of the National Park Service helped considerably in the field planning stage and we also thank the staff of the Lake Clark National Park and Preserve for their logistical support. This work was supported by The Paleoclimate Program (ATM-02-02898) of the National Science Foundation (NSF) and by The College of Wooster.

References cited: D’Arrigo, R.D., Mashig, E., Frank, D., Jacoby, G., and Wilson, R., 2004, Reconstructed warm season temperatures for Nome, Seward Peninsula, Alaska: Geophysical Research Letters, v. 31, L09202, doi:10.1029/2004GL019756.

Fritts, H., 1976, Tree rings and climate: Academic, San Diego, CA.

Stokes, M.A., and Smiley, T.L., 1968, An introduction to tree-ring dating: Chicago, IL.