department of earth and environmental sciences 106 geoscience

ML:2

DEPARTMENT OF EARTH AND ENVIRONMENTAL SCIENCES106 GEOSCIENCE, L-DEOCOLUMBIA UNIVERSITY

TO: FACULTY, GRADUATE STUDENTS , AND RESEARCH STAFF

FROM: MISSY PINCKERT

RE: ANNUAL DISSERTATION TOPIC LIST(ORALS PASSED THROUGH SPRING ´08)

DATE: 8/15/08

NAME DATE ORALS PASSED ADVISORY COMMITTEE

SHAHLA ALI 3/06 B. Anderson Stute Winckler

Helium Isotope and Rare Gas concentrations in Rocks

My thesis work applies the principles of Noble Gas IsotopeChemistry to two different topics, namely Helium isotopeconcentrations found in the marine record as a proxy forfreshwater input from melting icebergs to the Southern Oceanand the distribution of rare gas concentrations in matrix fluidsrecovered from cores obtained at depth in the San AndreasFault.

1. Freshwater budgets at sites of deep water formationinfluence the strength of the thermohaline circulation, whichprovides an important ocean atmosphere link to millennial scaleclimate change. Melting icebergs can be an important source offreshwater in Polar Regions. Ice rafted debris layers in marinesediment are used as indicators of melting icebergs, but theyoffer little information about the volume of ice involved. Inthis project, I am exploring the use of 3-He as a tracer for thevolume of freshwater released by melting icebergs. 3-He iscontained in Interplanetary Dust Particles (IDPs) which areaccumulated in ice and marine sediments at a known rate.Because they are incorporated throughout the ice sheet, IDPsare released wherever icebergs melt.

2. The presence of superhydrostatic fluid pressures is used toexplain the low friction slip along the San Andreas Fault Zone.

We are testing this hypothesis by direct sampling of coresobtained at depth in the San Andreas Fault and measuring thedistribution of rare gas concentrations in matrix fluids. U/Thdecay-series-elements and K decay in rock produce 4-He and40-Ar as well as nucleogenic (21,22Ne) and fissiogenic(132,134,136Xe) rare gases. The entire suite of measured noblegas isotopes (3,4He, 20, 21, 22Ne, 36, 38,40Ar, 84,86Kr, and129,131, 132, 134, 136Xe) are used to separate the non-atmospheric (produced and accumulated) from the atmosphericnoble gas components. Rare gas concentrations in the matrixfluids are used to investigate fluid flow and constrainmechanics of earthquake rupture in the San Andreas Fault.

No change since 7/07.

PETER ALMASI 3/03 deMenocal Cane

North Atlantic Holocene Paleoceanography and MillennialClimate Cycles.

North Atlantic climate has varied on centennial tomillennial time scales throughout the Holocene. To assessthe magnitude and spatial pattern of sea surfacetemperature (SST) changes during the Holocene, thefeasibility of paired planktonic d18O and Mg/Ca isassessed. Reconstructions are generated for three sub-polarsediment cores at 40-60 year time resolution from 0-14000BP.

I. Assessing paired d18O and Mg/Ca in the Holocene NorthAtlanticThe potential of paired Mg/Ca and d18O measurements toresolve 1-2 °C SST variability in the Holocene NorthAtlantic was evaluated in G. bulloides and N. pachyderma(d.) foraminifera. Individual components of external(calibration) and internal (measurement) errors werederived from existing calibrations, core tops from thisstudy, and tests of cleaning procedures and laboratoryreproducibility. To test the sensitivity of Mg/Ca in G.bulloides and N. pachyderma (d.) across a sub-polar NorthAtlantic SST gradient, paired Mg/Ca and d18O weremeasured in 7 core top samples containing post-1950radiocarbon. An exponential curve fit to Mg/Ca vs. d18O-derived calcification temperature yielded the relationMg/Ca=0.851±0.052*e^(0.074±0.006*T). Mg/Ca from N.pachyderma (d.) does not appear sensitive to calcificationtemperature in these samples, an unexpected result thatmay reflect sample dissolution during intense cleaningprocedures.

II. Holocene climate from d18O and Mg/Ca in G. bulloidesdown-core recordsSurface water proxy reconstructions of temperature andsalinity can provide insight into mechanisms of centennial-millennial Holocene climate change by the magnitude andspatial pattern of their variability. Foraminiferal d18O andMg/Ca from cores in the central and eastern North Atlanticsuggest that temperature and salinity varied up to 3°Cduring centennial to millennial cycles throughout theHolocene. Modern gradients in foraminiferal d18O andMg/Ca were maintained between coring sites on the BjörnDrift (Reykjanes Ridge) and Feni Drift (eastern RockallPlateau) within sample replicate error throughout theHolocene. This suggests climate change in the spatialpattern representing southward movement of the sub-polarfront during centennial to millennial scale cooling. Shifts inmillennial-scale reconstructed d18O and Mg/Ca are moreconsistent between the central and eastern North Atlanticcores than with petrologic tracer indicators of drift ice orcosmogenic proxies for solar variability.

JENNIFER ALLTOP 4/08 Rind Del Genio Gong

Will be submitted when she returns from field work inSeptember.

JENNIFER ARBUSZEWSKI 4/08 deMenocal B. Anderson Cane

A Global Multi-species Mg/Ca Calibration

In the past, temperature was thought to be the primary controlon Mg uptake in foraminifera. This dependency gave rise tothe Mg/Ca temperature proxy, which is frequently used inpaleoceanographic studies. However,we have recentlydiscovered what appears to be a salinity effect on on the Mg/Casignal recorded in planktonic foraminifera. This effect causesexcess Mg to be taken up by planktonic forams in high salinity(or alkalinity) regions. We have developed a new set ofcalibration equations for the Atlantic Ocean using pairedMg/Ca and delta 18O measurements, along with the deltacarbonate, to predict for temperature and salinity. Preliminaryresults indicate that these equations are robust. My thesis workaims to extend this study globally with the goal of determiningglobal equations for temperature and salinity for three speciesof planktonic foraminifera (G. ruber (white), G. sacculifer, andG. bulloides) using coretop samples and validating those

results. Additionally, I will be analyzing samples fromplankton tows (using the same three species) to confirm thecoretop results. I will also be working with LA-ICP-MS, SEMand other instruments to try to better understand how Mgheterogeneities in the foraminiferal shells may be linked to theexcess Mg we observe. These results should be widelyapplicable to paleoceanographic studies and may allow moreaccurate reconstructions of both temperature and salinity in thepast.

ZAHID AZIZ 11/05 Stute Schlosser van Geen

Local hydrology and arsenic (As) concentrations in shallowaquifers of Araihazar, Bangladesh.

Arsenic (As) is highly toxic but a common element foundin the atmosphere, soils, and natural waters. However, Asin drinking water probably poses the greatest threat tohuman health – ingested As causes cancer of the skin,bladder, and lung, and has been linked to other healtheffects, including reproductive and developmental effects,cardiovascular disease, and skin lesions. In term of drinkingwater standard, WHO and US-EPA permissible limit for Asis 10 ug/L. In Bangladesh 30% of wells have elevatedconcentrations of As considering the Bangladesh standard50 ug/L, which put approximately 35 millions people atrisk. If we follow the WHO guideline, 46% exceed the limitand 57 million people are exposed. At the shallow depth(<30 m) of aquifers where hydrogeology and geochemistryare dynamic, this scenario get worse - 55% of wells exceedthe safe limit. I am interested to take a closer look at thisshallow part of aquifers to understand subsurface processesthat control As concentrations in groundwater. My studyarea is in Araihazar, Bangladesh where six thousands wellshave been tested for As concentrations. Nearly 60% ofshallow wells (<30 m) in Araihazar have elevatedconcentrations of As and show a wide range of variability(1-1000 ug/L) both spatially and seasonally.

In my first chapter, I compared dissolved As concentrationsin 5200 shallow wells with the nature of surface soilsmapped with EM31 conductivity meter (a hand heldgeophysical instrument). The study showed thatelectromagnetic (EM) conductivity reading reflects the claypercentage and the recharge capability of surface soils. Ialso found that low dissolved As corresponds to areaswhere EM conductivities of surface soils are also low andvice versa. Based on these observations we concluded that

local recharge inhibits As concentrations from rising inshallow aquifers.

In second chapter, I tracked both physical and chemicalprocesses that control dissolved As in shallow aquifers byinstalling a series of very shallow multilevel (depths rangefrom 3 to 9m) monitoring wells at three different sites. Aseasonal variation was observed in groundwater chemistryat one multilevel wells site related to a simple mixingbetween two water masses with different chemicalcompositions and depths. This mixing process wasattributed to recharge processes controlled by the seasonalchanges in vertical and horizontal flow directions. Data atthis site also suggests a trapping mechanism of As inshallow aquifers that could explain about 50% of the spatialvariability in As concentration in Bangladesh. Besides,groundwater chemistry and relative hydraulic headmeasurements at two other multilevel sites support thenotion that long term irrigation pumping can lower the Asconcentration in shallow aquifers.

The final chapter includes a numerical groundwater modelwhere I made an attempt to explain the observations andprocesses discussed in the second chapter. The groundwaterflow model was simulated using the computer code knownas "modflow" through a commercial interface GMS 6.0.

Over all, these works suggest that local hydrology plays animportant role in the distribution of dissolved As in shallowaquifers.

DALIA BACH 3/07 Lerner-Lam Kushnir Uriate

Multi-scale landslide hazard and risk assessment: amodeling and multivariate statistical approach

AMY BALANOFF 4/07 Norell Flynn Olsen

The evolutionary history of Oviraptorosaur dinosaurs

Oviraptorosaurs are an unusual group theropod dinosaurswho possess an array of avian-like features. Thesemorphological similarities between birds andoviraptorosaurs are used in some phylogenetic analyses topropose a close relationship between the two groups. Otheranalyses, however, suggest that this clade, along with

therizinosaurs, is most closely related to Paraves(Deinonychosaurs + Avialae). In order to more fullyunderstand the placement oviraptorosaurs withinTheropoda the relationships within this less inclusive cladeneed to be resolved, yet most trees for Oviraptorosauriaconflict with one another. Therefore, I propose to performa phylogenetic analysis of the relationships withinoviraptorosaur dinosaurs to help place this important groupwithin a larger evolutionary context.


ROB BIALAS 4/07 Buck Lerner-Lam Weissel

The Effects of Temperature, Sedimentation, and Erosion onExtensional Systems

The rifting of continental lithosphere can be accommodatedin different ways, including narrow rifts, wide rifts, andcore complexes. Many different factors can influence thestyle of extension expressed at a rift. Using numerical andanalytical techniques, I will explore the effects of differenttemperature regimes, sedimentation, and erosion onextensional systems. These results are compared withgravity, seismic, topography, and geological data fromdifferent rifted systems, both active and ancient, to gaininsight into these systems. My current work has focused onthe West Antarctic Rift System and the Gulf of California.


ANTONIO BUONO 5/08 Walker Ebel Kelemen

An experimental study of the formation and evolution ofplanetary cores.

We are using high-pressure/high-temperature techniques tostudy partitioning between the inner and outer cores ofsmall planets, as well as the phase equilibrium that maygovern the composition of those cores.

MERRY CAI 10/04 Goldstein Spiegelman Plank

My thesis using isotope geochemistry in three projectsinvolving two different tectonic settings. The first project isabout subduction zone volcanism in the central and easternpart of the Trans Mexican Volcanic Belt. Using major and

trace element chemistry of arc lavas together with Nd-Hf-Pb-Sr isotope tracers I will quantify the contributions fromthe subducting oceanic plate and its overlying sediments tothe arc mantle source.

The second project focuses on the western MexicanVolcanic Belt, where ultrapotassic arc lavas eruptcontemporaneously with normal arc calc-alkaline lavas.This chapter of my thesis will attempt to find a sourceenrichment model to explain the occurrence of both typesof lava which will further our understanding of howsubduction changes the composition of the mantle wedge.

The third project is focused on an ultra-slow spreadingridge, the Gakkel Ridge in the Arctic ocean. Recentgeological and geochemical surveys revealed that not onlyabundant volcanism exist at Gakkel ridge, the lavassampled from the Gakkel ridge encompass global scalechemical variability. My thesis will try to examine twomajor questions. One is the relative importance oflithosphere thickness and mantle temperature on thegenesis of ocean ridge basalts. The other is the "veinedmantle" hypothesis, which argues that small extent ofmelting preferentially sample the enriched components inthe mantle and therefore produces higher heterogeneity inmid-ocean-ridge basalts. I will carry out a comprehensiveisotope geochemistry study and use the geochemical data totest these models.

LI CAO 3/05 Fairbanks Goldstein B. Anderson

The radiocarbon reservoir age of surface ocean water (thedifference between the 14C age of the ocean surface and thatof the atmosphere) reflects the balance among 14Cproduction, the spatial variability and magnitude of 14CO2flux across the air-sea interface, oceanic circulation, andmixing with 14C-depleted intermediate and deep waters. Forthe pre-anthropogenic ocean the sea surface 14C reservoirage is about 300 - 400 years in tropical oceans andincreases to 1200 years at higher latitudes in the SouthernOcean and the North Pacific. By contrast, there is littlesurface reservoir age gradient in the North Atlantic Oceanbetween 40°N and 70°N. The radiocarbon reservoir age ofthese surface waters is almost constant, at about 400-500years.

The radiocarbon reservoir age of the ocean surface water isessential for linking the continental and marine climate

records. I aim to measure the surface water reservoir ageusing fossil corals.


ANN COOK 3/07 Goldberg Ryan Malinverno Menke

Gas hydrate filled fractures in marine sediments: Insight intoa unique methane reservoir.

I propose to study the distribution and composition ofnatural gas hydrate filled fractures in unconsolidated marinesediments using data collected during the Chevron/DOE GasHydrate JIP Expedition 1 (JIP1) in May 2005, the IndianNational Gas Hydrate Program Expedition 1 (NGHP-1) inMay-August 2006, and the Chevron/DOE Gas Hydrate JIPExpedition 2 planned for spring of 2009.

Gas hydrate distribution and saturation is evaluated usingwell logs and borehole images integrated with pressurecores, sediment cores and seismic surveys. Borehole imagesfrom both JIP1 and NGHP-1 depict gas hydrate primarilyresiding in quasi-vertical planar fractures. These fracturesare generally well ordered and associated with the localshallow stress regime. Analysis of two borehole imagesexhibiting well ordered fractures from the same drill site inNGHP-1 suggests fractures tend to be small local featuresextending only a few meters and occur in a sequesteredinterval within the gas hydrate stability zone.

Additionally, quasi-vertical gas hydrate filled fractureseffect the accuracy of several borehole measurements,especially resistivity. Because the resistivity measurement isprimarily used to determine hydrate saturation, currentresearch is focused on the effect of fracture anisotropy onresistivity.

MARTIN COLLIER 3/07 Spiegelman Kelemen Goldstein

Inferences about melt transport, chemical interactions and themantle source beneath mid-ocean ridges from spatial variabilityin global MORB geochemistry

Although I am generally interested in the dynamics andchemistry of partially molten regions throughout Earth's crustand mantle (past and present), my graduate research has

become focused on the magmatic systems underlying mid-ocean ridges, which are favored by many geoscientists for their"simplicity". Advised by professors Marc Spiegelman and PeterKelemen, my work pursues two main objectives, 1) predictingchanges in magma chemistry caused by various phases of mid-ocean ridge basalt (MORB) petrogenesis using the approachof fluid dynamical modelling integrated withgeochemical/petrological calculations and 2) comparingpredictions from my models with global and regionalcompilations of MORB geochemistry. Results from thisresearch are allowing for new and quantitative tests of MORBformation and evolution models, with potentially more generalimplications for the sensitivity of geochemistry to geodynamicvariables.

WEI DU 5/08 Walker Kelemen Harlow

Grossular-pyrope Garnet Series Solution Properties

Garnet on the join Mg3Al2Si3O12 – Ca3Al2Si3O12(pyrope-grossular) is considered to be one of the mostimportant solid solutions in the Earth’s crust and uppermantle. Agreement between the different models of garnetmixing properties based on former experimental data is notvery satisfactory. So in my thesis, I will present the unitcell parameters of garnet solid solutions on the pyrope-grossular join synthesized at Lamont-Doherty EarthObservatory (LDEO) using multi-anvil technique andmeasured by X-ray diffraction at Lawrence-BerkeleyNational Laboratory. I measured the volume changes in thisgarnet solid solution between 25 and ~600°C andcalculated the excess volume and thermal expansion in thistemperature region. By fitting my new data to a thermaldynamic model, the new coexisting PT region for twophases garnet with composition on this pyrope-grossularjoin will be found and we will also hope to know how theconsolute temperature changes with pressure. Then I willcompare the modeling result with the following phaseseparation experiment result. And also I will check somenatural garnets to see how their growing PT conditions willchange concerning my new data and the revised thermaldynamic model.

ANDRES GIALLOMBARDO 4/06 Flynn Norell Christie-Blick

New cretaceous mammals from Mongolia and the earlydiversification of eutheria.

For their great diversity, complete (in comparative terms)fossil record, and well-studied life history, mammals (andparticularly fossil mammals) have played a major role inour understanding of evolution. Many key concepts andideas originated on the study of mammals were laterapplied to the more general theory of evolution.

The initial part of my research will consist on describingtwo newly discovered and fairly complete Cretaceouseutherians from the Gobi desert. Mesozoic eutherians arerare and usually fragmentary, and any addition has apotential large impact on our understanding of earlyeutherian diversification. Moreover, the two new taxa seemto be related to two of the most controversial groups inmammalian systematics, Zalambdalestidae and Zhelestidae.I will add these two new taxa and 20 other genera ofeutherians to a recently published data matrix (63 taxa, 408characters) (Wible et al. 2007), and perform a cladisticanalysis based on morphology, using parsimony as theoptimality criterion.

Currently, there are three competing general hypothesesabout the timing of mammalian evolution: long fuse, shortfuse and explosive radiation models. I expect the outcomeof my phylogenetic analysis to support one model morethan the other two. Constraining the time of origin of themore successful group of living mammals (Placentalia)would allow a better idea of the context in which thatprocess took place. In turn, this will make possible toaddress questions such as the role that continentalfragmentation, climate change, the K-T mass extinction,etc. played in driving eutherian and placental mammalianevolution.


BRENT GOEHRING 3/08 Schaefer Schlosser Peteet

Cosmogenic nuclide systematics and applications toclimate research

My research broadly focuses on the refinement anddevelopment of cosmogenic nuclide systematics andapplications to questions in geomorphology and climatechange. Although surface exposure dating usingcosmogenic nuclides has proliferated in the literaturerecently, we are only beginning to understand the fullpotential of surface exposure dating, as well as the pitfallsof the method. Currently, a better understanding of theproduction rate of the various cosmogenic nuclides is mostneeded, followed by a better understanding of productionscaling with geographic position, atmospheric depth, andinfluences of the geomagnetic field. To this end, part of myresearch includes production rate calibration studies inmultiple locations for the nuclides 10Be, 26Al, and in situ14C. The former two nuclides are widely measured, whilethe latter is currently measured infrequently due to thedifficulty of extraction and the existence of only a singlelab with extraction capabilities. To make in situ 14C, withits many advantages by itself or when combined with othernuclides, I have established the second in situ 14C extractionlab worldwide. The lab at Lamont effectively doubles thenumber of 14C analyses available for surface exposuredating.

With a better understanding of production rate systematics,we can begin to apply cosmogenic nuclides in new andnovel applications. One project involves a betterunderstanding of cosmogenic nuclide inheritance in glacialsystems, as well as the deposition age of glacialgeomorphologies in the Scoresby Sund region of eastGreenland. Until very recently, it was previously thoughtthat the accurate dating of moraines with surface exposuredating on historical timescales would prove to beprohibitively difficult. A second project is to establish ageson presumed Little Ice Age moraines deposited by cirqueglaciers in the Cascade Mountains of Washington Statewith the aim to better understand the structure of Little IceAge climate variations. Finally, recent evidence suggeststhat glaciers in the European Alps and worldwide varied insize over the Holocene. In theory, if subglacial erosion islow enough, the bedrock in front of a glacier should recorda history of advance and retreat of the glacier front. Mygoal is to use the nuclides 10Be and 14C to extract a historyof glacier front variations, and hence climate change, from

the concentration of the above two nuclides in the bedrock.This work will involve the measurement of low levels ofboth nuclides, presenting a methodological challenge, aswell as a better understanding of subglacial erosion ratesand application of glaciological modeling linked to a modelof cosmogenic nuclide production and decay.

AMY GUAN 3/06 Ou Gordon Chen

A numerical study of shear dispersion in the benthic layerand thermocline.

R. CHADWICK HOLMES 4/05 Webb Tolstoy Menke

Crustal Structure Variations in Mid-Ocean RidgeEnvironments

Advances in ocean bottom instrumentation and seismicdata analysis have offered marine scientists a clearerpicture of oceanic crustal structure. Yet with clarity comescomplication; studies now indicate oceanic crust can varysignificantly from the classic ~6 km thick velocity modelcomprising three gradient-defined layers bounded by asharp discontinuity at the Moho. Much of this variabilityoccurs near plate boundaries, particularly in closeproximity to mid-ocean ridge systems where new crust iscontinuously created. Does this reflect local stressdifferences changing the thickness of young lithosphere,inhomogeneities in the upper asthenosphere leading to non-uniform melting and underplating, or more regionaldifferences at the whole plate level? What controlsthickness differences between individual seismic "layers,"and can this vertically-stratified velocity model trulydescribe the physical structure of oceanic crust?

In my thesis, I examine these issues by analyzing thecrustal velocity structure within several different tectonicsettings. Using data captured by ocean bottom instrumentshydrophones (OBHs) and ocean bottom seismometers(OBSs), I explore:

1. The structure of young (~6 Ma) oceanic crust in thesouthern East Pacific Rise region with a 2-D seismicrefraction line crossing non-hotspot ridge systemsseemingly unrelated to normal mid-ocean ridge processes.

2. The variation in crustal thickness along the SoutheastIndian Ridge (SEIR) from seismic refraction data collectedalong several ridge segments that show a progressivechange in axial depth, axial morphology, and the presenceand depth of an axial magma chamber even though theparent melt source and spreading rate (~72 mm/yr) remainnearly constant.

3. The difference in crustal structure to either side of theBirubi Transform, which separates the robust axial highalong zone A of the SEIR from the characteristically deepand chaotic segment B5 within the Australian AntarcticDiscordance (AAD). As an extension of the previous SEIRseismic refraction study, these results offer new insight intothe variability of accretionary processes and upper mantledynamics associated with the AAD.

KEVIN JONES 3/06 Goldstein Hemming B. Anderson

Exploring Neodymium Isotopes of Seawater in the Modernand Ancient Oceans.

My dissertation focuses on the study neodymium (Nd)isotopes in seawater and in iron-manganese (Fe-Mn) oxy-hydroxide sediments to further explore their usefulness as apaleoceanographic tracer. I am using an ocean generalcirculation model to better understand Nd isotopes in themodern ocean and to identify the importance of internalsources in different ocean basins. Additionally, I amanalyzing seawater collected near the coast of South Africato test for the existence of internal sources of Nd in thisregion. In the same study area I will also compare the Ndisotope composition of proximal Holocene Fe-Mn oxy-hydroxide sediments from the same depths to determinetheir ability to record the Nd isotopes of modern seawater.If I find that the sediments do accurately record the Ndisotopes of seawater in this region and that internal sourcesof Nd are absent, then I will analyze sediments dating backto the Last Glacial Maximum (~18,000 years ago) todetermine whether or not ocean circulation was differentduring this period of drastically different climate.


KATIE LEONARD 3/06 Christie-Blick Tremblay MacAyeal

Antarctic Snow Drift Processes

My research combines numerical modeling, fieldobservations, and remote sensing to study the redistributionof snow by the wind, with particular emphases on the roleof drift in reshaping the Antarctic ice sheet surface andfresh water input to the southern ocean. Aeolian transportof snow is important in many environments due to climaticand fresh water budget implications, but is principallystudied at the interface between snowy regions and society,e.g. in relation to avalanching, or road management andconstruction. Snow drift is also a potentially significant butpoorly understood component of the mass balance of theAntarctic ice sheet. The redistribution of snow by the windcan lead to substantial errors in local estimates of ice sheetmass balance as determined from stratigraphic methods.Such point measurements are used as checks for massbalance and ice sheet models, and understanding driftprocesses should provide better estimates of the error ofsuch measurements. Additionally, the amount of snowblown off the edges of the continent into the SouthernOcean is very poorly constrained, and may be as much as10% of the total annual snowfall over Antarctica. Whenthis snow leaves the ice sheet it plays a role in sea ice andpolynya formation as well as air-sea interaction over openwater.


JINBAO LI 4/05 Griffin Cook Peteet

Moisture Variability across China and Mongolia fromInstrumental Data and Tree-ring Records

China and Mongolia (CM) are located in a regioncharacterized by complex topography and climate. Due tothe varying effects of multiple climate forcings, moistureavailability within the CM varies dramatically.Understanding on the occurrence of droughts/floods overthis diverse area is limited, partly due to the shortness ofinstrumental data. In order to recover long-term moisturechanges, tree-ring analysis is essential, as growth rings oftrees provide the exactly-dated, annually resolved estimatesof past climate. My research is focused on developing alarge tree-ring network over China. Along with the

available data from Mongolia, we can reconstruct moisturevariability during the last several hundred years for muchof CM. With such a more complete record we are able tounderstand how moisture has varied and what are theforcings of its variability. This knowledge will help toimprove the prediction of moisture variations on annual todecadal and longer time scales.


ANDREW MADOF 3/07 Christie-Blick Anders Martinson

On the non-eustatic mechanisms modulating sedimentation:examples from offshore Louisiana and the eastern BookCliffs, western Colorado

DAVID McGEE 4/08 Anderson Broecker Winckler

Isotopic flux tracers: investigations of constant flux proxiesin the western North Atlantic, dust in the equatorial Pacific,and hydrothermal inputs at Mono Lake

My thesis research uses the tools of isotope geochemistryto investigate three separate questions related to past andpresent fluxes in ocean and lake settings.

1. Response of 3He and 230Th to sediment redistributionat the Blake Outer Ridge, western North AtlanticExtraterrestrial 3He and adsorbed 230Th are commonlyused to calculate fluxes in ocean sediments and to estimatelateral sediment advection. In both these applications, it isassumed that 3He and 230Th are evenly distributed amongdifferent sediment size classes. Some researchers havequestioned this assumption, suggesting that the use of 3Heand 230Th may be biased by grain size fractionation duringsediment resuspension and transport. This projectexamines these assumptions by measuring 3He and 230Thin sediments reflecting different amounts of lateraladvection and in different grain size fractions of thesediment.

2. Constraints on hydrothermal fluxes into Mono Lake,California from 36Cl and 3HeMono Lake is a closed-basin lake located in a volcanicallyactive region. Its solute balance thus reflects inputs bothfrom precipitation-fed surface runoff and groundwater and

from hydrothermal sources. Establishing the present stateof this balance will assist in determining the lake's age,evaluating potential sediment core proxies for lake salinity,and understanding the lake's unusual carbon budget andpast changes in the carbon reservoir age. In this project, weuse the very different 36Cl/35Cl ratios of hydrothermal andsurface inputs to constrain the balance of chloride sourcesto the lake. We also use 3He as an integrated tracer ofhydrothermal inputs to the lake. Sediment porewaterprofiles provide additional insights into the relationshipbetween infiltration of saline lake waters and upwelling offresher hydrothermal waters.

3. Dust provenance in the equatorial Pacific OceanRecent dust flux studies across the equatorial Pacific haveprovided important calibration data for models of dusttransport and deposition. In the western equatorial Pacific,flux data conflict with present dust models, indicatingmuch higher fluxes than models can reproduce. Information on dust provenance would provide keyconstraints for model improvement. This project willinvolve traditional isotopic provenance tools (Sr, Nd, andPb isotopes), trace element signatures, and novelprovenance techniques (4He/232Th ratios) to try to identifythe dominant dust source(s) in the equatorial Pacific, with aparticular focus on the western Pacific.

OUSMANE NDIAYE 11/05 Sobel Ward Martinson

"Predictability of Sahelian Climate Characteristics: rainfalltotal, intra-seasonal distribution and onset."

My thesis focuses on understanding and predicting Sahelianrainfall variability the rainy-season starting date, theseasonal total, and the seasonal distribution. A focus is onaspects of the rainy season that are known to have greatestenvironmental and social impact, and in addition. thepredictability of some of the impacts are directly assessed.The Sahel region is a transition zone between desert to theNorth (Sahara desert) and tropical forest to the South.Rainfall in this region strongly influences many aspects ofsociety, including agriculture (crop production andlivestock), water resources, and vector born diseaseoutbreaks (malaria is the by far the first cause of mortality).Predicting its variability can have a huge benefit for thesociety.

The first chapter deals with the predictability of the seasonalrainfall total. In addition to exploring the maximization ofskill using GCM model output statistics, I focus on a keyissue which is changes in SST anomalies that take place inboreal spring and that currently limit the lead-time ofseasonal predictions for the June-September rainfall season.One aim of the study is to provide a definitive analysis ofthis limitation, along with its reasons and possible avenuesto increase the lead-time of predictions. A comparison ofstatistical and dynamical methods will be made.

The second chapter investigates the extent to which thepredictability of large-scale circulation features can betranslated into an ability to provide information on smallspatial scales, and on the statistics of weather events throughthe season. These issues relate to how predictions can bemade for variables like crop yield and vegetation greenness,and environmentally influenced diseases such as malaria.Through analysis of datasets and model outputs, key spaceand timescale prediction issues will be addressed, along withsome key impact variables. The work will include morefocused and detailed analyses on Senegal, comprising thewesternmost zone of the Sahel, bordering the AtlanticOcean.

In the third chapter, I look at characteristics of theatmosphere (dynamic and energetic) during the onset of theseasonal rainfall in Senegal, and the predictability of theonset date. Well-defined local and regional circulationfeatures before and during rainfall onset in Senegal areidentified using observations (Precipitable Water, OLR andWind). The wind anomaly circulation at 850 hPa showswave-like propagations prior to and during the rainfall onset,including both eastward and westward propagating features.The extent to which these features are captured in a state-of-the science model is investigated using CFS ocean-atmosphere extended-range weather forecasts, with a viewto exploring predictability of the onset on the timescale ofseveral days to a few weeks.

STERLING NESBITT 10/06 Olsen Norell Christie-Blick

The relationships and rise of the archosaurs.

No response.

KORI NEWMAN 4/06 Menke Cormier Nedimovic

Application of new geophysics techniques on margins andridges.


PHILIP ORTON 3/06 Martinson McGillis Sobel

Coastal Ocean Turbulent Mixing and Air-Sea CO2 Fluxes

A major uncertainty in global carbon budgets andpredictions of future climate is the role of the tidal rivers,estuaries and the coastal ocean. My Ph.D. researchexamines the physical controls on air-water transfer ofcarbon dioxide in these systems, primarily the role andsources of turbulent mixing near the sea surface. Theoverriding goal is to address how numerical models canmost efficiently replicate this gas transfer, facilitating theinclusion of coastal ocean CO2 fluxes in global carbonbudgets and climate models. Possible components include:

Variability of internally generated turbulence in an estuary,from 100 days of continuous observations. In press,Continental Shelf Research. (with M. Visbeck): Recentpublications have developed a methodology called the“variance method” for remotely quantifying turbulencethrough the water column using Acoustic Doppler CurrentProfilers (ADCPs). We present detailed ADCP observationsof internally generated turbulence in a sheared, stratifiednatural flow, as well as an analysis of the external factorsleading to its generation and temporal variability.

Turbulence and stratification in the Hudson River estuary(with M. Visbeck, W. McGillis): This is the firstcomprehensive summary of stratification and turbulence inthe Hudson River estuary, including measurements from awide range of along-estuary locations, riverflow, and semi-diurnal tidal range.

Physical controls on air-water transfer of carbon dioxide in apartially mixed estuary (with W. McGillis, C. Zappa): I havebeen anchoring a small catamaran in the Hudson to makemeasurements of currents, turbulence, water column densitystructure, CO2 fluxes, and wind. I will analyze CO2 fluxdata against ambient forcing variables and compare theobservations against a series of theories and models ofincreasing complexity.

Physical controls on continental shelf air-sea CO2 fluxes:Autonomous in situ observations (with W. McGillis, J.Moisan): I was awarded a 2007 summer fellowship to utilizeNASA's autonomous 20' boat called OASIS (Ocean-Atmosphere Sensor Integration System) to study thephysical controls on continental shelf air-sea CO2 fluxes.An additional goal is to evaluate the potential for usingmultiple OASIS platforms, satellite remote sensing data, andmodel assimilation for a larger-scale study that coversmultiple shelf provinces and quantifies the global role ofcontinental shelves in the carbon cycle.


KANDAGA PUJIANA 3/08 Gordon Ou Martinson

The Makassar Strait dynamics at intraseasonal timescale

My research focuses on the energetic intraseasonalvariability [<90-day] in the main conduit of the IndonesianThroughflow, Makassar Strait. The plausible sources ofvariability vary from the oceanic and atmospheric featuresemanating from the Pacific and Indian Ocean such asRossby wave and Madden-Julian oscillation to the locallygenerated instability. The complete picture of the dynamicsis investigated in the realm of data analysis, analyticalapproach and numerical modeling.

BYRDIE RENIK 3/06 Christie-Blick Anders Kelemen

An evaluation of competing models for extension across theDeath Valley region, California-Nevada.

JOY ROMANSKI 5/03 Del Genio Rossow Sobel

Investigating the Role of Diabatic Heating in GlobalAtmospheric Circulation and Climate Sensitivity: AnEnergetics Approach

The circulation of the atmosphere is driven by the equator-to-pole temperature gradient. Exactly how this takes place,however, is the result of complex interactions among thevarious components of the climate system. One way to look atthese interactions is via the Lorenz energy cycle, which

describes the response of the atmosphere to different sources ofenergy.

This study focuses on the generation of the energy available todrive atmospheric circulation. Contributions to the zonal meanand eddy available potential energy from latent heating fromprecipitation, surface sensible heat fluxes and radiative fluxconvergence are examined to elucidate how the variousprocesses responsible for diabatic heating affect theatmospheric energetics.

The energy cycle is characteristic of a particular climate. Theextent to which it varies under different climates is investigatedusing model output generated for the Intergovernmental Panelon Climate Change's Fourth Assessment Report. Output frommodels exhibiting large and small sensitivity to doubled carbondioxide is examined to determine how the energy cycle mightchange in a warmer climate, and how these changes relate tothe models' climate sensitivity.


PAUL SCHMIEDER 4/06 Schlosser Ho Simpson

My research investigates the small scale mixing dynamicsand transport mechanisms associated with estuaries. Manycoastal waterways currently suffer from the effects ofurbanization and industrialization in the form of pollutedand contaminated water. To understand the impact ofcontamination, the hydrodynamics of these water bodiesmust be quantified. Through the use of deliberate tracerssuch as SF6 (sulfur hexafluoride), we can gain insight onhow mixing is affected by water stratification, rivergeometry, and tides. We can also use our tracer techniqueto quantify advection, dispersion, gas exchange, andresidence times for these water bodies.


ADRIENNE SMITH 3/08 Bell Buck Lerner-Lam

Recent observation has shown the subglacial water canpenetrate to the ice sheet bed and influence the velocity ofan ice sheet on a relatively short time scale. Questions thatthis raises and my work aims to answer are 1.) Can weimage the subglacial hydrological system? 2.) How is watertransported beneath an ice sheet, in channels or broader

flows? and 3.) What impact do subglacial processes haveon the long term stability of an ice sheet?

MICHELLE SPAULDING 4/08 Flynn Norell Christie-Blick

Phylogeny of the stem Carnivoramorpha

The living order Carnivora is one of the most diverse extantmammalian order. The fossil record of this order extends,undoubtedly, back to the early Paleocene, roughly 63million years ago. However, it is not until roughly 42million years ago that clear representatives of the crowngroup arise. The fossils found in the interim time (stemcarnivormorphans') have typically received little detailedstudy, and many previous treatments of the order tended tolump them into untested groupings, or ignore themcompletely. My research is focused upon these basalspecimens, in order to create a clear picture of the series ofevolutionary transformations that led to crown Carnivora.Questions that will be addressed, primarily, are thephylogeny of the basal taxa - is there a clear stem lineseries of taxa or several clades within the stem? andlocomotor behavior of primitive taxa, hoping to shed somelight on the primitive locomotor method of theCarnivoramorpha.

ABBY SPIELER 3/05 Schlosser Smethie Martinson

Transient tracer studies of ocean circulation in the ArcticOcean and Nordic Seas.


SANPISA SRITRAIRAT 3/07 Peteet Griffin deMenocal

Multiproxies analyses of past vegetation, climate, andsediment dynamics in Hudson River wetlands.


DANIELLE STROUP 3/08 Tolstoy Bohnenstiehl Menke

No response.

DEBRA TILLINGER 3/07 Gordon Ou Yuan

The Indonesian Throughflow and its variability.

The Indonesian Seas are only low latitude conduit in theworld ocean. Through their complex set of straits, theIndonesian Throughflow carries 10 million cubic meters ofwater per second from the Pacific Ocean to the IndianOcean, altering the heat and freshwater budgets of both.This flow is variable on multiple temporal and spatialscales.

The objective of my research is to investigate theinterannual time variability of the ITF transport and alongchannel speed with respect to El Nino-Southern Oscillationand the Indian Ocean Dipole Mode. The research will alsoinclude a broader examination of the role of the ITF inglobal heat transport. It will include observational in situdata from moorings in the Makassar Strait, the main routeof the Indonesian Throughflow. The work will alsoincorporate historical hydrographic data and model outputinto a framework of geophysical fluid dynamics.

No change since 7/07

JILL VAN TONGEREN 4/08 Kelemen Mathez Goldstein

Thermal and Chemical Evolution of the Bushveld UpperZone.

The Bushveld Complex is the world's largest layered maficintrusion and the only one of its kind with its roof stillintact. My dissertation focuses on the thermal andchemical evolution of the uppermost portions of theBushveld in order to understand the nature of heat loss anddifferentiation in large magma bodies. Focus will also beon how the magma chamber interacted with the rocks intowhich it was emplaced. Comparisons betweencrystallization and cooling in intra-continental layeredintrusions as well as mid-oceanic spreading centers willultimately be important in our understanding of igneouscrystallization in various tectonic settings.

CHRISTY VEEDER 3/06 Rind Schmidt Hemming

Modeling Climate and Production-related Impacts on Ice-coreBeryllium-10

In order to better understand contemporary climate changeand anthropogenic climate forcings, it is necessary toquantify solar forcing, the most significant natural forcingon centennial timescales. One way to learn more about pastsolar changes, particularly those on multi-decadal tocentennial timescales, is to study the ice-bound archives ofcosmogenic isotopes: substances that are produces bycollisions between galactic cosmic rays (GCR) andatmospheric oxygen and nitrogen. Examples of cosmogenicisotopes include beryllium-10 (Be10, half-life of 1.5 My),Be7 (half-life 53 days) and C14 (half-life 5730 years).Cosmogenic isotope production is related to solar magneticactivity, which modulates Earth's exposure to GCR flux.Changes in solar magnetic activity, in turn, have historicallybeen positively correlated with changes in solar irradiance,particularly over the course of the 11-year sunspot cycle.This relationship between cosmogenic isotopes, solarmagnetic activity and solar irradiance is the basis for thepotential use of substances like Be10 as proxies for solaractivity.

Beryllium-10 is particularly well suited for this purpose fortwo reasons: its long half life (compared to Be7) means thatit lasts long enough to record changes over glacial-interglacial timescales, and its short atmospheric residencetime (compared to C14) means that it can provide high-resolution time series in well-dated polar ice core records.

However, it is possible for climate changes -- which may ormay not be related to changes in solar irradiance -- toconfound solar signals in the Be10 record. Processes thataffect the distribution of Be10 in the troposphere -- such aschanges in stratosphere-troposphere exchange (STE) oraerosol scavenging efficiency, both of which may changewith climate -- could distort the degree to which ice corerecords reflect production changes. Similarly, because amore or less active hydrologic cycle may dilute orexaggerate Be10 snow concentrations, any process thataffects precipitation could also obscure a production-ratesignal. If Be10 is to be unambiguously used to infer solarvariation, we first need a way to account for the effects ofclimate as they appear in the ice core record. My thesis willapproach this issue in three different ways:

1. One set of modeling experiments will broadly examinehow production- and climate-related changes impact Be10deposition by separately looking at how changes inproduction and changes in climate (doubled CO2, reducedNADW production, volcanic eruptions) affect Be10,particularly over Greenland and Antarctica (the mainsources of the ice core data).

2. A second set of experiments will address the ways inwhich solar-related changes in both climate and productionaffect Be10 over during periods of reduced solar activitysuch as the Maunder Minimum.

3. Finally, a set of transient 20th-century simulations will beperformed to calibrate the ways in which which Be10 isrecorded differently in Greenland as opposed to Antarctica.The results of this experiment will have implications onunderstanding the degree to which solar activity over thepast century is unusually high with respect to the pastseveral millenia.

DAVID WANG 3/05 Cane Seager Chen

The changes of the Pacific ocean tropical thermocline inresponse to global warming

Both observational and modeling studies have shown thatthe tropical thermocline is ventilated via the shallowmeridional overturning circulation (aka. the subtropicalcells, STCs) by the extratropical surface waters. Thereforeboth the changes of the STCs and of the properties of theextratropical source waters are capable to alter thecharacteristics of the tropical thermocline. In this study, wewill first document the changes of the tropical thermoclinein the Pacific ocean from a suite of IPCC AR4 climatemodel scenario runs. Then we will use both a backtrackingtrajectory algorithm and a transport matrix-based adjointtracer method to quantify the changes of the locations andthe hydrographic properties of the source waters of thetropical thermocline as well is the ventilation pathways andthe transit time between the current climate and a warmerclimate. Since the tropical thermocline is one of the mostimportant components in the tropical ocean-atmosphereclimate and climate variability such as El Nino - SouthernOscillation, this study has the important implication ofbetter understanding how the tropical climate will respondto global warming.

KAREN WOVKULICH 4/07 Simpson Chillrud Stute Mailloux

Mobilization of Arsenic from Contaminated Sediments

My research focuses on arsenic cycling in the environmentand specifically on the mobilization of arsenic fromcontaminated sediments at the Vineland Chemical CompanySuperfund site in southern New Jersey. Arsenic is thesecond most common contaminant of concern at U.S.Superfund sites, and contaminated groundwater is oftenremediated using pump and treat technology. However,arsenic can sorb to iron and aluminum oxyhydroxides in thesediments making pump and treat remediation less effectiveand thus slower to reach the desired level of clean up, as hasbeen the case at Vineland. Therefore, my current researchaims to improve the efficiency of pump and treat byincreasing the mobilization of arsenic from the sedimentinto the groundwater that will then be treated. This researchinvolves laboratory experiments in which I make chemicalamendments to soil columns and monitor their effect onarsenic mobility as well as hydrological modeling and in situfield testing of the most promising chemical amendments. The information gained from these laboratory and fieldstudies should be applicable to numerous arseniccontaminated sites where pump and treat remediation iscurrently being used or where it may be used in the future.Additionally, what we learn from this work about factorsthat influence arsenic mobility may also help us understandarsenic cycling and mobilization in areas of the world wherenaturally occurring arsenic is contaminating groundwatersthat are used for drinking water supplies.

department of earth and environmental sciences 106 geoscience

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