AMS Radiocarbon Chronology of Glacier Fluctuations in the South Shetland Islands During the Last Glacial/Interglacial Hemicycle:Implications for Global Climate Change

This award supports a two year program to produce a new reconstruction of ice extent, elevation and thickness at the Last Glacial Maximum (LGM) for the South Shetland Islands in the Antarctic Peninsula. One field season on Livingston Island will involve mapping the areal extent and geomorphology of glacial drift and determining the elevation and distribution of trimlines. In addition, ice flow direction will be determined by mapping and measuring the elevation of erosional features and the position of erratic boulders. One of the main goals of this work will be to demonstrate whether or not organic material suitable for radiocarbon dating exists in the South Shetland Islands. If so, the age of the deposits will be determined by measuring the carbon-14 age of plant, algal, and fungal remains preserved at the base of the deposits, as well as incorporated marine shells, seal skin and other organic material that may be found in raised beach deposits. Another goal will be to concentrate on the development of relative sea-level curves from 2-3 key areas to show whether or not construction of such curves for the South Shetland Islands is possible. The new reconstruction of ice extent, elevation and thickness at the Last Glacial Maximum for the South Shetland Islands which will be produced by this work will be useful in studies of ocean circulation and ice dynamics in the vicinity of the Drake Passage. It will also contribute to the production of a deglacial chronology which will afford important clues about the mechanisms controlling ice retreat in this region of the southern hemisphere

POWRE: High-Resolution Chronology of Millennial-Scale Lake-Level Fluctuations in the Dry Valleys (Antarctica) From Uranium-Thorium and Radiocarbon Dating

The Professional Opportunities for Women in Research and Engineering (POWRE) program affords new research and educational enhancement opportunities for women scientists. This project, which addresses the fundamental problem of the cause of millennial-scale climate change, contains components specifically designed to increase the educational and research skills of the principal investigator. She will learn the following new information/skills: 1) thermal ionization mass spectrometry (TIMS) uranium/thorium (U/TH) dating with Dr. G. Henderson at Lamont-Doherty Earth Observatory (LDEO) and Oxford University, 2) millennial-scale climate change with Drs. W. Broecker and G. Bond, LDEO, and with Drs. D. Oppo and L. Keigwin, Woods Hole Oceanographic Institution, 3) Antarctic limnology with Dr. C. Hendy, University of Waikato, and 4) regional climate modeling with Dr. K. Maasch, University of Maine. She will then apply her new knowledge and skills to a study of millennial-scale fluctuations of lake levels in the Dry Valleys of Antarctica. The investigator will use TIMS, U/TH and accelerator mass spectrometric (AMS) radiocarbon dating of lacustrine carbonates to test the reservoir effect in order to ensure that the chronology of lake-level fluctuations in accurate. She will then use her knowledge of millennial-scale fluctuations to determine if the lake variations are similar to those seen elsewhere in the world. Knowledge of limnology will help not only to assess the lake reservoir effect, but also to begin to determine the cause of large-scale changes in lake level. Likewise, regional climate modeling will allow her to gain insight into the energy balance and wind patterns of the Dry Valleys region during the last glacial maximum. These new skills will benefit the P.I., not only in this particular project relating to Antarctic lakes, but also in her future Antarctic and Southern Hemisphere research in New Zealand and Patagonia

Collaborative Research: Timing and Structure of the Last Glacial Maximum and Termination in Southern Peru: Implications for the Role of the Tropics in Climate Change

The role of the tropics in climate change has important implications for understanding both orbital-scale and abrupt climate variations. Yet our ability to assess tropical behavior during major climate events, such as the last glacial maximum (LGM), is limited by poor spatial coverage and insufficient control on sample ages. This project will address this problem by developing well-dated records of glacial fluctuations from the LGM through the termination and late-glacial period at Nevados Coropuna and Allinccapac in southern Peru and use these data in numerical simulations of glacier mass balance and local climate. These sites allow an examination of glacier variations, as well as coeval snowline changes, along a transect from the arid (Coropuna) to the humid (Allinccapac) Andes and thus document how major climate events may have been expressed in areas with distinctly different environments. This work consists of detailed mapping of moraines; precise surface-exposure age dating (3He and 10Be) of carefully selected boulders from moraine crests and drift edges; basal 14C ages of bogs interspersed among moraines; calculation of former snowline depression; and modeling of the relationship between glacier mass-balance changes and climate. The work will be an important step towards understanding tropical behavior and will finally allow a thorough testing of the Milankovitch hypothesis of ice ages in the tropics.Broader Impacts: This research educates and trains students, a postdoc, and a recent female Ph.D. There is a lecture series on local geology and global climate change given to eco-tourism students at the University of Arequipa, as well as lectures to the Lima archaeology department. K-12 students benefit through a long-standing associations with classrooms in rural, commonly economically disadvantaged Maine. The project maintains a website and is exploring a learning module. In addition, the research is part of a joint initiative to understand land use and settlement patterns of the first Americans in the Peruvian highlands

Collaborative Research: Grounding-line Retreat in the Southern Ross Sea - Constraints from Scott Glacier

This award supports a project to investigate late Pleistocene and Holocene changes in Scott Glacier, a key outlet glacier that flows directly into the Ross Sea just west of the present-day West Antarctic Ice Sheet (WAIS) grounding line. The overarching goals are to understand changes in WAIS configuration in the Ross Sea sector at and since the last glacial maximum (LGM) and to determine whether Holocene retreat observed in the Ross Embayment has ended or if it is still ongoing. To address these goals, moraine and drift sequences associated with Scott Glacier will be mapped and dated and ice thickness, surface velocity and surface mass balance will be measured to constrain an ice-flow model of the glacier. This model will be used to help interpret the dated geologic sequences. The intellectual merit of the project relates to gaining a better understanding of the West Antarctic Ice Sheet and how changing activity of fast-flowing outlet glaciers and ice streams exerts strong control on the mass balance of the ice sheet. Previous work suggests that grounding-line retreat in the Ross Sea continued into the late Holocene and left open the possibility of ongoing deglaciation as part of a long-term trend. Results from Reedy Glacier, an outlet glacier just behind the grounding line, suggest that retreat may have slowed substantially over the past 2000 years and perhaps even stopped. By coupling the work on Scott Glacier with recent data from Reedy Glacier, the grounding-line position will be bracketed and it should be possible to establish whether the retreat has truly ended or if it is ongoing. The broader impacts of the work relate to the societal relevance of an improved understanding of the West Antarctic ice sheet to establish how it will respond to current and possible future environmental changes. The work addresses this key goal of the West Antarctic Ice Sheet Initiative, as well as the International Polar Year focus on ice sheet history and dynamics. The work will develop future scientists through the education and training of one undergraduate and two Ph.D. students, interaction with K-12 students through classroom visits, web-based \u27expedition\u27 journals, letters from the field, and discussions with teachers. Results from this project will be posted with previous exposure dating results from Antarctica, on the University of Washington Cosmogenic Nuclide Lab website, which also provides information about chemical procedures and calculation methods to other scientists working with cosmogenic nuclides

Collaborative Research: Abandoned Elephant Seal Colonies in Antarctica: Integration of Genetic, Isotopic, and Geologic Approaches toward Understanding Holocene Environmental Change

During previous NSF-sponsored research, the PI\u27s discovered that southern elephant seal colonies once existed along the Victoria Land coast (VLC) of Antarctica, a region where they are no longer observed. Molted seal skin and hair occur along 300 km of coastline, more than 1000 km from any extant colony. The last record of a seal at a former colony site is at ~A.D. 1600. Because abandonment occurred prior to subantarctic sealing, disappearance of the VLC colony probably was due to environmental factors, possibly cooling and encroachment of land-fast, perennial sea ice that made access to haul-out sites difficult. The record of seal inhabitation along the VLC, therefore, has potential as a proxy for climate change. Elephant seals are a predominantly subantarctic species with circumpolar distribution. Genetic studies have revealed significant differentiation among populations, particularly with regard to that at Macquarie I., which is the extant population nearest to the abandoned VLC colony. Not only is the Macquarie population unique genetically, but it is has undergone unexplained decline of 2%/yr over the last 50 years3. In a pilot study, genetic analyses showed a close relationship between the VLC seals and those at Macquarie I. An understanding of the relationship between the two populations, as well as of the environmental pressures that led to the demise of the VLC colonies, will provide a better understanding of present-day population genetic structure, the effect of environmental change on seal populations, and possibly the reasons underlying the modern decline at Macquarie Island.This project addresses several key research problems: (1) Why did elephant seals colonize and then abandon the VLC? (2) What does the elephant seal record reveal about Holocene climate change and sea-ice conditions? (3) What were the foraging strategies of the seals and did these strategies change over time as climate varied? (4) How does the genetic structure of the VLC seals relate to extant populations? (5) How did genetic diversity change over time and with colony decline? (6) Using ancient samples to estimate mtDNA mutation rates, what can be learned about VLC population dynamics over time? (7) What was the ecological relationship between elephant seals and Adelie penguins that occupied the same sites, but apparently at different times? The proposed work includes the professional training of young researchers and incorporation of data into graduate and undergraduate courses

Collaborative Research: Chronology of Ice Fluctuations in the South Shetland Islands Since the Last Glacial Maximum

This award supports a study of the timing of climate changes in the Southern Hemisphere with the goal of reconstructing former ice extent and fluctuations, as well as paleoclimate, along the key latitudinal transect from temperate Tierra del Fuego to the polar Antarctic Peninsula. Samples already in hand will allow the dating of ice fluctuations in the South Shetland Islands (SSI), a critical location where that transect crosses the Antarctic Convergence. Surprisingly little concrete evidence exists concerning former ice extent in the island chain. The results of this study will answer a number of basic questions regarding ice extent and the timing of subsequent deglaciation in the Antarctic Peninsula. A cosmogenic exposure-age chronology will be produced from samples collected at carefully selected moraines on King George and Livingston Islands. A preliminary age of 18,000 years for a large granodiorite boulder from the outer moraine at Marian Cove suggests that the moraine may represent the Last Glacial Maximum (LGM) ice position. These data point to the potential for developing a ~20,000-yr record of ice fluctuations in the SSI, something that has not been achieved previously. Such data could be used not only to settle the long-standing debate over LGM ice extent in the SSI, but also would be valuable in assessing the global synchrony of large climate changes. Both a graduate and undergraduate student will be involved. This work builds on the recent success in dating glacial deposits in the Antarctic as young as 300 years using Beryllium-10 (10Be), as well as on an unexpected opportunity to map moraines and collect exposure-age samples in the SSI in 2002/2003. This research will produce a new understanding of the timing of ice fluctuations in the SSI, the extent and thickness of former ice cover, and may allow the development of a glacial chronology extending from the LGM to the late Holocene. This work will also provide a basis for inter-hemispheric comparisons of climate change and fits within the constraints of the Pole-Equator-Pole (PEP 1) transect to develop high-resolution, well-dated paleoclimate records in the Americas and Antarctic Peninsula

The Science Behind Climate Change: A Journey to Reedy Glacier

This Communicating Research to Public Audiences project focuses on the Reedy Glacier Antarctic research of Brenda Hall (OPP 0229034) and its relevance to the residents of and visitors to Maine. Collaborators include the University of Maine, the Maine Discovery Museum, the Acadia National Park and Cadillac Mountain Sports (an environmentally active retail company with several stores around the state). The primary deliverable is the development of an interactive software program that presents information and experiences in a two-tiered concept approach -- on the Reedy Glacier and its connection to Maine and on the process of science. The software is being configured into kiosks at the three partnering organizations, into a DVD format for informal and formal settings to be distributed at cost and onto a University of Maine Climate Change web portal currently under separate development. The project web site will provide source code for the portal design so others may use it to create portals and modules of their own. The Maine Discovery Museum intends to create additional exhibitry on the topic with resources outside this proposal, and the Acadia National Park will use the programs in teacher education workshops

Putting the West Antarctic Ice Sheet into Context

This award supports a project to develop new insights into the cause and pattern of events during the last glacial termination in South America and Antarctica. One emerging view is that a warming Southern Ocean (SO), driven by a chain of events initiated in the Northern Hemisphere (NH) and tied to the interhemispheric climate seesaw of the last termination, was the underlying mechanism that drove the West Antarctic ice sheet (WAIS) from its Late Glacial Maximum (LGM) position back to present-day grounding lines. This ocean thermal forcing would have impacted WAIS by accelerating basal melt rates on fringing floating ice shelves and tongues. The validity of such a proposition can be examined from detailed chronologies of ice retreat at a variety of middle to high latitude sites. From such chronologies, it can be determined whether or not the intervals of ice recession form a pattern that fits the timing of warming pulses known to have occurred in the SO during the termination. The intellectual merit of this project is that it will test the proposition that warming pulses in the SO, driven by NH stadials, are the key events that culminated in recession of WAIS to its present-day configuration, setting up the possibility of irreversible collapse. This test is based on placing into a global context the timing and structure of glacial recession along a transect from the southernmost Andes to the Ross Embayment. This project will examine the middle of the transect, by establishing the chronology of ice recession following the LGM in southernmost South America and on the northern Antarctic Peninsula. Because of the abundance of datable terrestrial organic material in association with glacial deposits ?the most rapid progress will be made by starting in southernmost South America. Specifically, cores will be collected from numerous bogs located between the LGM limit and present-day ice in Cordillera Darwin and on Isla Hoste, and use 14C dates of basal organic remains to develop a chronology for ice recession. The broader impacts of this work include a commitment to education and outreach. This work will educate a graduate student and material from this grant will be used in college courses, as well as in presentations to elementary and middle schools and to senior communities. This proposal does not require field work in the Antarctic

Variations in Ice Rafted Detritus on Beaches in the South Shetland Islands: A Possible Climate Proxy

Raised beach ridges on Livingston Island of the South Shetland Islands display variations in both quantity and source of ice rafted detritus (IRD) received over time. Whereas the modem beach exhibits little IRD, all of which is of local origin, the next highest beach (similar to250 C-14 yr BP) has large amounts, some of which comes from as far away as the Antarctic Peninsula. Significant quantities of IRD also were deposited similar to 1750 C-14 yr BP. Both time periods coincide with generally cooler regional conditions and, at least in the case of the similar to250 yr old beach, local glacial advance. We suggest that the increases in ice rafting may reflect periods of greater glacial activity, altered ocean circulation, and/or greater iceberg preservation during the late Holocene. Limited IRD and lack of far-travelled erratics on the modem beach are both consistent with the ongoing warming trend in the Antarctic Peninsula region

Sensitivity of the Antarctic Ice Sheet to Climate Change over the Last Two Glacial/Interglacial Cycles

This award supports a project to investigate the sensitivity of the Antarctic ice sheet (AIS) to global climate change over the last two Glacial/Interglacial cycles. The intellectual merit of the project is that despite its importance to Earth\u27s climate system, we currently lack a full understanding of AIS sensitivity to global climate change. This project will reconstruct and precisely date the history of marine-based ice in the Ross Sea sector over the last two glacial/interglacial cycles, which will enable a better understanding of the potential driving mechanisms (i.e., sea-level rise, ice dynamics, ocean temperature variations) for ice fluctuations. This will also help to place present ice?]sheet behavior in a long-term context. During the last glacial maximum (LGM), the AIS is known to have filled the Ross Embayment and although much has been done both in the marine and terrestrial settings to constrain its extent, the chronology of the ice sheet, particularly the timing and duration of the maximum and the pattern of initial recession, remains uncertain. In addition, virtually nothing is known of the penultimate glaciation, other than it is presumed to have been generally similar to the LGM. These shortcomings greatly limit our ability to understand AIS evolution and the driving mechanisms behind ice sheet fluctuations. This project will develop a detailed record of ice extent and chronology in the western Ross Embayment for not only the LGM, but also for the penultimate glaciation (Stage 6), from well-dated glacial geologic data in the Royal Society Range. Chronology will come primarily from high-precision Accelerator Mass Spectrometry (AMS) Carbon-14 (14C) and multi-collector Inductively Coupled Plasma (ICP)-Mass Spectrometry (MS) 234Uranium/230Thorium dating of lake algae and carbonates known to be widespread in the proposed field area. The broader impacts of this work are that it fits well within the West Antarctic Ice Sheet initiative and complements the ANDRILL program. In addition, the PIs are committed to and have a long record of student education and outreach at all levels. A number of students (4-6) will be mentored in this project. The PI regularly visits classrooms to talk about Antarctica and communicates with students from the field and participates in local outreach efforts to attract girls to earth science