@article {2964, title = {Ice-sheet expansion from the Ross Sea into McMurdo Sound, Antarctica, during the last two glaciations}, journal = {Quaternary Science Reviews}, volume = {278}, year = {2022}, month = {Jan-02-2022}, pages = {107379}, abstract = {An understanding of Antarctic Ice Sheet (AIS) behavior is important for future sea-level predictions. Here, we examine past ice-sheet history in the McMurdo Sound region of the western Ross Sea over the last two glacial-interglacial cycles in order to gain insight into the drivers of ice-sheet change. Surficial mapping, along with radiocarbon dates of lacustrine algae and uranium-thorium disequilibrium dates of lacustrine carbonates from ice-dammed lakes, allow reconstruction of the timing and origin of grounded ice in McMurdo Sound during the last glacial maximum (LGM) and penultimate glaciation. During the LGM, ice-surface elevation profiles and distribution of erratics indicate ice flow into southern McMurdo Sound from the Ross Sea, rather than seaward expansion of local glaciers from the Royal Society Range. The grounded ice in McMurdo Sound flowed westward to block the mouths of valleys in the Royal Society Range and to dam proglacial lakes. In Marshall Valley, maximum ice extent during what is termed the Ross Sea glaciation, was achieved by 18 ka and remained close to this position until after 14 ka. The pattern of surficial deposits suggests that ice during the penultimate glaciation, locally named the Marshall glaciation, was slightly more extensive than that of the LGM but had a similar Ross Sea origin. Maximum ice extent in Marshall Valley occurred at \~{}145{\textendash}150 ka; the grounded ice may have receded from the valley mouth shortly after 138 ka. Both ice expansions occurred broadly during times of low Antarctic air temperatures, which have been linked to insolation minima. However, the lack of widespread surface melting ablation zones on the AIS indicates that the link between ice expansion and orbital forcing is likely to be indirect and possibly driven through the ocean. Closer examination of the precise timing of the glacial maxima in Marshall Valley shows that the Marshall glaciation occurred synchronously with the penultimate global maximum; ice recession took place during Termination II. In contrast, maximum ice extent during the Ross Sea glaciation along the Royal Society Range occurred after the global LGM, during Termination I. Deglaciation was primarily an early Holocene event. We attribute this delayed maximum and deglaciation (relative to global events) to the effect of rising accumulation on ice-sheet mass balance.}, issn = {02773791}, doi = {10.1016/j.quascirev.2022.107379}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0277379122000105}, author = {Heath, Stephanie and Hall, Brenda L. and Denton, George H. and Henderson, Gideon M. and Hendy, Chris H.} } @article {2982, title = {Relative sea-level data preclude major late Holocene ice-mass change in Pine Island Bay}, journal = {Nature Geoscience}, volume = {15}, year = {2022}, month = {06/2022}, pages = {568-573}, abstract = {The rapidly retreating Thwaites and Pine Island glaciers together dominate present-day ice loss from the West Antarctic Ice Sheet and are implicated in runaway deglaciation scenarios. Knowledge of whether these glaciers were substantially smaller in the mid-Holocene and subsequently recovered to their present extents is important for assessing whether current ice recession is irreversible. Here we reconstruct relative sea-level change from radiocarbon-dated raised beaches at sites immediately seawards of these glaciers, allowing us to examine the response of the earth to loading and unloading of ice in the Amundsen Sea region. We find that relative sea level fell steadily over the past 5.5 kyr without rate changes that would characterize large-scale ice re-expansion. Moreover, current bedrock uplift rates are an order of magnitude greater than the rate of long-term relative sea-level fall, suggesting a change in regional crustal unloading and implying that the present deglaciation may be unprecedented in the past 5.5 kyr. While we cannot preclude minor grounding-line fluctuations, our data are explained most easily by early Holocene deglaciation followed by relatively stable ice positions until recent times and imply that Thwaites and Pine Island glaciers have not been substantially smaller than present during the past 5.5 kyr.}, doi = {10.1038/s41561-022-00961-y}, url = {https://www.nature.com/articles/s41561-022-00961-y}, author = {Braddock, Scott and Hall, Brenda L. and Johnson, Joanne S. and Balco, Greg and Spoth, Meghan and Whitehouse, Pippa L. and Campbell, Seth and Goehring, Brent M. and Rood, Dylan H. and Woodward, John} } @article {johnson_review_2022, title = {Review article: Existing and potential evidence for Holocene grounding line retreat and readvance in Antarctica}, journal = {The Cryosphere}, volume = {16}, number = {5}, year = {2022}, note = {Publisher: Copernicus GmbH}, month = {05/2022}, pages = {1543{\textendash}1562}, abstract = {Widespread existing geological records from above the modern ice sheet surface and outboard of the current ice margin show that the Antarctic Ice Sheet (AIS) was much more extensive at the Last Glacial Maximum (\~{}20 ka) than at present. However, whether it was ever smaller than present during the last few millennia, and (if so) by how much, is known only for a few locations because direct evidence lies within or beneath the ice sheet, which is challenging to access. Here, we describe how retreat and readvance (henceforth {\textquotedblleft}readvance{\textquotedblright}) of AIS grounding lines during the Holocene could be detected and quantified using subglacial bedrock, subglacial sediments, marine sediment cores, relative sea-level (RSL) records, geodetic observations, radar data, and ice cores. Of these, only subglacial bedrock and subglacial sediments can provide direct evidence for readvance. Marine archives are of limited utility because readvance commonly covers evidence of earlier retreat. Nevertheless, stratigraphic transitions documenting change in environment may provide support for direct evidence from subglacial records, as can the presence of transgressions in RSL records, and isostatic subsidence. With independent age control, ice structure revealed by radar can be used to infer past changes in ice flow and geometry, and therefore potential readvance. Since ice cores capture changes in surface mass balance, elevation, and atmospheric and oceanic circulation that are known to drive grounding line migration, they also have potential for identifying readvance. A multidisciplinary approach is likely to provide the strongest evidence for or against a smaller-than-present AIS in the Holocene.}, issn = {1994-0416}, doi = {10.5194/tc-16-1543-2022}, url = {https://tc.copernicus.org/articles/16/1543/2022/}, author = {Johnson, Joanne S. and Venturelli, Ryan A. and Balco, Greg and Allen, Claire S. and Braddock, Scott and Campbell, Seth and Goehring, Brent M. and Hall, Brenda L. and Neff, Peter D. and Nichols, Keir A. and Rood, Dylan H. and Thomas, Elizabeth R. and Woodward, John} } @article {2802, title = {Antarctic Relic Microbial Mat Community Revealed by Metagenomics and Metatranscriptomics}, journal = {Frontiers in Ecology and Evolution}, volume = {7}, year = {2019}, month = {Nov-01-2020}, abstract = {Buried upslope from the modern lakes in the McMurdo Dry Valleys of Antarctica are relict lake deposits embedded in valley walls. Within these relict deposits, ancient microbial mats, or paleomats, have been preserved under extremely arid and cold conditions since the receding of larger paleolakes thousands of years ago, and now serve as a sheltered niche for microbes in a highly challenging oligotrophic environment. To explore whether paleomats could be repositories for ancient lake cells or were later colonized by soil microbes, determine what types of metabolic pathways might be present, analyze potential gene expression, and explore whether the cells are in a vegetative or dormant state, we collected paleomat samples from ancient lake facies on the northern slopes of Lake Vanda in Wright Valley in December 2016. Using a gentle lysis technique optimized to preserve longer molecules, combined with a polyenzymatic treatment to maximize yields from different cell types, we isolated high-molecular weight DNA and RNA from ancient paleomat samples. Community composition analysis suggests that the paleomat community may retain a population of indigenous mat cells that may flourish once more favorable conditions are met. In addition to harboring a diverse microbial community, paleomats appear to host heterotrophs in surrounding soils utilizing the deposits as a carbon source. Whole genome long-read PacBio sequencing of native DNA and Illumina metagenomic sequencing of size-sorted DNA (>2,500 nt) indicated possible cell viability, with mat community composed of bacterial taxa. Metagenome assemblies identified genes with predicted roles in nitrogen cycling and complex carbohydrate degradation, and we identified key metabolic pathways such as stress response, DNA repair, and sporulation. Metatranscriptomic data revealed that the most abundant transcripts code for products involved in genetic information processing pathways, particularly translation, DNA replication, and DNA repair. Our results lend new insight into the functional ecology of paleomat deposits, with implications for our understanding of cell biology, Antarctic microbiology and biogeography, and the limits of life in extremely harsh environments.}, doi = {10.3389/fevo.2019.00001}, url = {https://www.frontiersin.org/article/10.3389/fevo.2019.00001/full}, author = {Zaikova, Elena and Goerlitz, David S. and Tighe, Scott W. and Wagner, Nicole Y. and Bai, Yu and Hall, Brenda L. and Bevilacqua, Julie G. and Weng, Margaret M. and Samuels-Fair, Maya D. and Johnson, Sarah Stewart} } @article {2801, title = {Asynchronous behavior of the Antarctic Ice Sheet and local glaciers during and since Termination 1, Salmon Valley, Antarctica}, journal = {Earth and Planetary Science Letters}, volume = {482}, year = {2018}, month = {Jan-01-2018}, pages = {396 - 406}, abstract = {The stability of the Antarctic Ice Sheet under future warming remains an open question with broad implications for sea-level prediction and adaptation. In particular, knowledge of whether the ice sheet has the capacity for rapid drawdown or collapse, or whether it can remain stable during periods of warming, is essential for predicting its future behavior. Here we use 55 radiocarbon dates, coupled with geomorphologic mapping, to reconstruct the timing of changes in ice extent and elevation during the last ice-age termination in Salmon Valley, adjacent to McMurdo Sound in the western Ross Sea Embayment. Results indicate that a grounded ice sheet in the Ross Sea Embayment achieved its maximum elevation and extent along the headlands of Salmon Valley at \~{}18,000 yr BP, during a period of increasing temperatures and accumulation over the Antarctic continent. This ice remained at or near its maximum on the headlands near the valley mouth until after \~{}14,000 yr BP. Removal of grounded Ross Sea ice from Salmon Valley was complete shortly after \~{}7900 yr BP, indicating that the grounding line had retreated through southern McMurdo Sound by that time. We suggest the primary driver of Ross Sea ice removal from McMurdo Sound was marine-based, either through basal melting or calving due to sea-level rise. When combined with regional data, the Salmon Valley record suggests that this sector of the Antarctic Ice Sheet did not contribute in a significant way to deglacial meltwater pulses, such as meltwater pulse 1a. In contrast to the Ross Sea ice, our work also shows that local, independent alpine glaciers in Salmon Valley have advanced through the Holocene. Land-terminating glaciers such as these elsewhere in the region show a similar pattern, and may reflect the continued influence of increased accumulation following the termination of the last ice age.}, keywords = {Antarctic Ice Sheet, glacial geomorphology, ice sheet stability, Termination I}, issn = {0012821X}, doi = {10.1016/j.epsl.2017.11.038}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0012821X1730674X}, author = {Jackson, Margaret S. and Hall, Brenda L. and Denton, George H.} } @article {2529, title = {Holocene climate and environmental history of East Greenland inferred from lake sediments}, journal = {Journal of Paleolimnology}, volume = {57}, year = {2017}, month = {Jan-04-2017}, pages = {321 - 341}, abstract = {Prediction of future Arctic climate and environmental changes, as well as associated ice-sheet behavior, requires placing present-day warming and reduced ice extent into a long-term context. Here we present a record of Holocene climate and glacier fluctuations inferred from the paleolimnology of small lakes near Istorvet ice cap in East Greenland. Calibrated radiocarbon dates of organic remains indicate deglaciation of the region before ~10,500 years BP, after which time the ice cap receded rapidly to a position similar to or less extensive than present, and lake sediments shifted from glacio-lacustrine clay to relatively organic-rich gyttja. The lack of glacio-lacustrine sediments throughout most of the record suggests that the ice cap was similar to or smaller than present throughout most of the Holocene. This restricted ice extent suggests that climate was similar to or warmer than present, in keeping with other records from Greenland that indicate a warm early and middle Holocene. Middle Holocene magnetic susceptibility oscillations, with a ~200-year frequency in one of the lakes, may relate to solar influence on local catchment processes. Following thousands of years of restricted extent, Istorvet ice cap advanced to within 365 m of its late Holocene limit at ~AD 1150. Variability in the timing of glacial and climate fluctuations, as well as of sediment organic content changes among East Greenland lacustrine records, may be a consequence of local factors, such as elevation, continentality, water depth, turbidity, and seabirds, and highlights the need for a detailed spatial array of datasets to address questions about Holocene climate change.}, keywords = {De Vries cycle, Glacially fed lakes, Greenland, Holocene, Paleoclimate}, issn = {0921-2728}, doi = {10.1007/s10933-017-9951-5}, url = {http://link.springer.com/10.1007/s10933-017-9951-5}, author = {Lusas, Amanda R. and Hall, Brenda L. and Lowell, Thomas V. and Kelly, Meredith A. and Bennike, Ole and Levy, Laura B. and Honsaker, William} } @article {2610, title = {Timing and magnitude of early to middle Holocene warming in East Greenland inferred from chironomids}, journal = {Boreas}, volume = {4611126123715949514747452279282108875423653331285492025312166523481473253855431029263383391243655482254028102024461441564827316}, year = {2017}, month = {Jan-10-2017}, pages = {678 - 687}, abstract = {Much of Greenland experienced summers warmer than present in parts of the early to middle Holocene, during a precession-driven positive anomaly in summer insolation. However, the magnitude of that warmth remains poorly known, and its timing and spatial pattern are uncertain. Here we describe the first quantitative Holocene palaeotemperature reconstruction from central East Greenland based upon insect (chironomid) assemblages preserved in lake sediments. We postulate that landscapes like our study site, characterized by minimal soil and vegetation development through the Holocene and thus little influenced by some important secondary gradients, are especially well suited to the use of chironomids to reconstruct Holocene temperatures. The inferred timing of warmth at our study site near Scoresby Sund agrees well with other nearby evidence, including glacial geological reconstructions and temperatures inferred from precipitation isotopes at Renland ice cap, supporting the use of chironomids to reconstruct temperatures at this site. We infer highest temperatures from c. 10 to 5.5 ka, followed by gradual cooling after 5.5 ka and progressively colder and less productive conditions after 3.5 ka. Models based upon two independent training sets yield similar inferred temperature trends, and suggest an average summer temperature anomaly from c. 10 to 5.5 ka of 3 to 4 {\textdegree}C relative to the preindustrial last millennium. The estimated overall rate of Neoglacial cooling averaged over the period from 5.5 to 0.5 ka was 0.6 to 0.8 {\textdegree}C per thousand years, more than twice the rate previously estimated for the Arctic as a whole. Given strong apparent spatial variability in Holocene climate around the Arctic, and the utility of palaeoclimate data for improving climate and ice-sheet models, it should be a priority to further quantify past temperature changes around the margins of the Greenland Ice Sheet, where few quantitative reconstructions exist and future warming will affect global sea level. }, doi = {10.1111/bor.2017.46.issue-410.1111/bor.12247}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/bor.12247}, author = {Axford, Yarrow and Levy, Laura B. and Kelly, Meredith A. and Francis, Donna R. and Hall, Brenda L. and Langdon, Peter G. and Lowell, Thomas V.}, editor = {{\'\i}nguez-Rodrigo, M. and Baquedano, E. and Mabulla, A. and {\'\i}n, F. and Egeland, C. P.} } @article {52, title = {Ad{\'e}lie penguin dietary remains reveal Holocene environmental changes in the western Ross Sea (Antarctica)}, journal = {Palaeogeography, Palaeoclimatology, Palaeoecology}, volume = {395}, year = {2014}, note = {id: 2347}, pages = {21-28}, abstract = {Carbon and nitrogen stable isotope analyses were performed on modern and Holocene Ad{\'e}lie penguin guano samples collected from ornithogenic soils along the Scott Coast (Southern Victoria Land, Antarctica), from Cape Irizar to Dunlop Island, and at Cape Bird (Ross Island). Guano samples also were sieved and sorted under stereomicroscope in order to select penguin dietary remains, such as fish bones and otoliths. Carbon and nitrogen stable isotope composition, coupled with the taxonomic identification of fish otoliths from Scott Coast Holocene samples, indicated a mainly fish-based diet for this area, with Pleuragramma antarcticum as the most eaten prey throughout the investigated period (from 390 cal BP to ca 7300 cal BP). The isotopic values of Ross Island samples (from modern to 3850 cal BP) showed a krill consumption increase in the samples younger than 2000 cal BP, with the maximum in modern samples. Scott Coast and Ross Island Holocene samples showed δ13C and δ15N trends similar to those previously published from Terra Nova Bay (northern Victoria Land), whereas modern samples from Ross Island have similar δ15N composition but different δ13C values. This δ13C divergence started at ca 2000 BP and follows the abandonment of the Scott Coast colonies. The δ13C trend observed in Ross Island and Terra Nova Bay samples and the abandonment of the Scott Coast colonies could suggest the stability and the persistence of the previous oceanographic conditions (i.e. polynya) for the Terra Nova Bay area and the establishment of new conditions for water circulation in the Southern Ross Sea since ~ 2000 BP when persistent sea-ice sealed the Scott Coast.}, issn = {0031-0182}, doi = {10.1016/j.palaeo.2013.12.014}, url = {http://www.sciencedirect.com/science/article/pii/S0031018213005440}, author = {Lorenzini, Sandra and Baroni, Carlo and Baneschi, Ilaria and Salvatore, Maria Cristina and Fallick, Anthony E. and Hall, Brenda L.} } @article {54, title = {Holocene fluctuations of Bregne ice cap, Scoresby Sund, east Greenland: a proxy for climate along the Greenland Ice Sheet margin}, journal = {APEX II: Arctic Palaeoclimate and its Extremes}, volume = {92}, year = {2014}, pages = {357-368}, abstract = {The Greenland Ice Sheet is a major component of the Arctic cryosphere and the magnitude of its response to future climate changes remains uncertain. Longer-term records of climate near the ice sheet margin provide information about natural climate variability and can be used to understand the causes of past changes in the Greenland Ice Sheet. As a proxy for Holocene climate near the ice sheet margin, we reconstruct the fluctuations of Bregne ice cap in the Scoresby Sund region of central east Greenland. Bregne is a small ice cap (2.5 km2 in area) and responds sensitively to summer temperatures. We employ a multi-proxy approach to reconstruct the ice cap fluctuations using geomorphic mapping, 10Be ages of boulders and bedrock and lake sediment records. Past extents of Bregne ice cap are marked by moraines and registered by sediments in downvalley lakes. 10Be ages of bedrock and boulders outboard of the moraines indicate that Bregne ice cap was within \~{}250 m of its present-day limit by at least 10.7 ka. Multi-proxy data from sediments in Two Move lake, located downvalley from Bregne ice cap, indicate that the ice cap likely completely disappeared during early and middle Holocene time. Increasing magnetic susceptibility and percent clastic material from \~{}6.5 to \~{}1.9 cal ka BP in Two Move lake sediments suggest progressively colder conditions and increased snow accumulation on the highlands west of the lake. Laminated silt deposited at \~{}2.6 cal ka BP and \~{}1.9 cal ka BP to present registers the onset and persistence of Bregne ice cap during the late Holocene. 10Be ages of boulders on an unweathered, unvegetated moraine in the Bregne ice cap forefield range from 0.74 to 9.60 ka. The youngest 10Be age (0.74 ka) likely represents the age of the moraine whereas older ages may be due to 10Be inherited from prior periods of exposure. This late Holocene moraine marks the second largest advance of the ice cap since deglaciation of the region at the end of the last ice age. The oldest moraine in the forefield dates to <=2.6 cal ka BP. The fluctuations of Bregne ice cap were likely influenced by Northern Hemisphere summer insolation throughout the Holocene and abrupt late Holocene cold events.}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2013.06.024}, url = {http://www.sciencedirect.com/science/article/pii/S0277379113002448}, author = {Levy, Laura B. and Kelly, Meredith A. and Lowell, Thomas V. and Hall, Brenda L. and Hempel, Laura A. and Honsaker, William M. and Lusas, Amanda R. and Howley, Jennifer A. and Axford, Yarrow L.} } @article {104, title = {Extensive recession of Cordillera Darwin glaciers in southernmost South America during Heinrich Stadial 1}, journal = {Quaternary Science Reviews}, volume = {62}, year = {2013}, note = {id: 2331}, pages = {49-55}, abstract = {The geographic expression and phasing of events during the last termination are important for isolating mechanisms that caused Earth to emerge from the last ice age. Heinrich Stadial 1 (HS1; 14,600{\textendash}18,000 yr BP) is a key because of the central role that its far-field effects had on the last termination in the Southern Hemisphere. Here, we present new data from Cordillera Darwin that show rapid glacier recession in southern South America during HS1. This retreat was coeval with ice recession elsewhere in South America and New Zealand, with increased upwelling in the Southern Ocean, with warming of SSTs offshore of Chile, and with a rise in atmospheric CO2. Together, these data indicate a coherent and rapid response to the effects of HS1 in the middle and high latitudes of the Southern Hemisphere.}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2012.11.026}, url = {http://www.sciencedirect.com/science/article/pii/S0277379112005057}, author = {Hall, Brenda L. and Porter, Charles T. and Denton, George H. and Lowell, Thomas V. and Bromley, Gordon R. M.} } @article {92, title = {Late Holocene expansion of Istorvet ice cap, Liverpool Land, east Greenland}, journal = {Quaternary Science Reviews}, volume = {63}, year = {2013}, note = {id: 2290}, pages = {128-140}, abstract = {The Greenland Ice Sheet is undergoing dynamic changes that will have global implications if they continue into the future. In this regard, an understanding of how the ice sheet responded to past climate changes affords a baseline for anticipating future behavior. Small, independent ice caps adjacent to the Greenland Ice Sheet (hereinafter called {\textquotedblleft}local ice caps{\textquotedblright}) are sensitive indicators of the response of Greenland ice-marginal zones to climate change. Therefore, we reconstructed late Holocene ice-marginal fluctuations of the local Istorvet ice cap in east Greenland, using radiocarbon dates of subfossil plants, 10Be dates of surface boulders, and analyses of sediment cores from both threshold and control lakes. During the last termination, the Istorvet ice cap had retreated close to its maximum Holocene position by \~{}11,730 cal yr BP. Radiocarbon dates of subfossil plants exposed by recent recession of the ice margin indicate that the Istorvet cap was smaller than at present from AD 200 to AD 1025. Sediments from a threshold lake show no glacial input until the ice cap advanced to within 365 m of its Holocene maximum position by \~{}AD 1150. Thereafter the ice cap remained at or close to this position until at least AD 1660. The timing of this, the most extensive of the Holocene, expansion is similar to that recorded at some glaciers in the Alps and in southern Alaska. However, in contrast to these other regions, the expansion in east Greenland at AD 1150 appears to have been very close to, if not at, a maximum Holocene value. Comparison of the Istorvet ice-cap fluctuations with Holocene glacier extents in Southern Hemisphere middle-to-high latitude locations on the Antarctic Peninsula and in the Andes and the Southern Alps suggests an out-of-phase relationship. If correct, this pattern supports the hypothesis that a bipolar see-saw of oceanic and/or atmospheric circulation during the Holocene produced asynchronous glacier response at some localities in the two polar hemispheres.}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2012.11.012}, url = {http://www.sciencedirect.com/science/article/pii/S0277379112004830}, author = {Lowell, Thomas V. and Hall, Brenda L. and Kelly, Meredith A. and Bennike, Ole and Lusas, Amanda R. and Honsaker, William and Smith, Colby A. and Levy, Laura B. and Travis, Scott and Denton, George H.} } @article {2440, title = {Constant Holocene Southern-Ocean 14C reservoir ages and ice-shelf flow rates}, volume = {296}, year = {2010}, month = {2010/7/15/}, pages = {115 - 123}, abstract = {Southern Ocean radiocarbon reservoir ages (i.e. non-zero radiocarbon ages in seawater) are the highest in the world{\textquoteright}s surface ocean. Constraining these reservoir ages at present and in the past is important not only because unknown reservoir ages limit the interpretation of Antarctic radiocarbon chronologies, but also because reservoir ages provide information about ocean circulation (as a recorder of past circulation and as an end member for major deep-water masses in today{\textquoteright}s ocean). In this study, we use paired U/Th and 14C ages of an unusual set of solitary coral samples trapped by fringing ice shelves in the Ross Sea to provide the first detailed study of Holocene reservoir ages for the Southern Ocean. Our results indicate a relatively constant marine radiocarbon reservoir age of 1144 {\textpm} 120 years for the past 6000 years. These results are consistent with extrapolation of the relationship between 14C and alkalinity seen elsewhere, supporting the use of this empirical relationship in high latitudes. The results also suggest constant deep-ocean circulation and air{\textendash}sea exchange during the Holocene and provide a good target for tuning ocean models of modern circulation. Combining the new ages for corals with their distance from the modern-day ice-shelf grounding line provides some of the first long-term records of ice-shelf velocities for any region and indicates constant flow of the McMurdo Ice Shelf during the Holocene, at a rate similar to that observed today.}, keywords = {coral, marine reservoir effect, McMurdo Ice Shelf, radiocarbon, Southern Ocean, U/Th dating}, isbn = {0012-821X}, doi = {10.1016/j.epsl.2010.04.054}, url = {http://www.sciencedirect.com/science/article/pii/S0012821X10003067}, author = {Hall, Brenda L. and Henderson, Gideon M. and Baroni, Carlo and Kellogg, Thomas B.} } @article { ISI:000279905800011, title = {Constant Holocene Southern-Ocean C-14 reservoir ages and ice-shelf flow rates}, journal = {EARTH AND PLANETARY SCIENCE LETTERS}, volume = {296}, number = {{1-2}}, year = {2010}, month = {JUL 15}, pages = {115-123}, type = {Article}, abstract = {Southern Ocean radiocarbon reservoir ages (i.e. non-zero radiocarbon ages in seawater) are the highest in the world{\textquoteright}s surface ocean. Constraining these reservoir ages at present and in the past is important not only because unknown reservoir ages limit the interpretation of Antarctic radiocarbon chronologies, but also because reservoir ages provide information about ocean circulation (as a recorder of past circulation and as an end member for major deep-water masses in today{\textquoteright}s ocean). In this study, we use paired U/Th and C-14 ages of an unusual set of solitary coral samples trapped by fringing ice shelves in the Ross Sea to provide the first detailed study of Holocene reservoir ages for the Southern Ocean. Our results indicate a relatively constant marine radiocarbon reservoir age of 1144 +/- 120 years for the past 6000 years. These results are consistent with extrapolation of the relationship between C-14 and alkalinity seen elsewhere, supporting the use of this empirical relationship in high latitudes. The results also suggest constant deep-ocean circulation and air-sea exchange during the Holocene and provide a good target for tuning ocean models of modern circulation. Combining the new ages for corals with their distance from the modern-day ice-shelf grounding line provides some of the first long-term records of ice-shelf velocities for any region and indicates constant flow of the McMurdo Ice Shelf during the Holocene, at a rate similar to that observed today. (C) 2010 Elsevier B.V. All rights reserved.}, keywords = {coral, marine reservoir effect, McMurdo Ice Shelf, radiocarbon, Southern Ocean, U/Th dating}, issn = {0012-821X}, doi = {10.1016/j.epsl.2010.04.054}, author = {Hall, Brenda L. and Henderson, Gideon M. and Baroni, Carlo and Kellogg, Thomas B.} } @article {297, title = {Rapid Response of a Marine Mammal Species to Holocene Climate and Habitat Change}, journal = {Plos Genetics}, volume = {5}, year = {2009}, note = {id: 1914; PT: J; NR: 58; TC: 11; J9: PLOS GENET; PG: 11; GA: 486SZ; UT: WOS:000269219500031}, pages = {e1000554-e1000554}, abstract = {Environmental change drives demographic and evolutionary processes that determine diversity within and among species. Tracking these processes during periods of change reveals mechanisms for the establishment of populations and provides predictive data on response to potential future impacts, including those caused by anthropogenic climate change. Here we show how a highly mobile marine species responded to the gain and loss of new breeding habitat. Southern elephant seal, Mirounga leonina, remains were found along the Victoria Land Coast (VLC) in the Ross Sea, Antarctica, 2,500 km from the nearest extant breeding site on Macquarie Island (MQ). This habitat was released after retreat of the grounded ice sheet in the Ross Sea Embayment 7,500-8,000 cal YBP, and is within the range of modern foraging excursions from the MQ colony. Using ancient mtDNA and coalescent models, we tracked the population dynamics of the now extinct VLC colony and the connectivity between this and extant breeding sites. We found a clear expansion signal in the VLC population similar to 8,000 YBP, followed by directional migration away from VLC and the loss of diversity at similar to 1,000 YBP, when sea ice is thought to have expanded. Our data suggest that VLC seals came initially from MQ and that some returned there once the VLC habitat was lost, similar to 7,000 years later. We track the founder-extinction dynamics of a population from inception to extinction in the context of Holocene climate change and present evidence that an unexpectedly diverse, differentiated breeding population was founded from a distant source population soon after habitat became available.}, issn = {1553-7390}, doi = {10.1371/journal.pgen.1000554}, author = {de Bruyn, Mark and Hall, Brenda L. and Chauke, Lucas F. and Baroni, Carlo and Koch, Paul L. and Hoelzel, A. Rus} } @conference {1648, title = {The Holocene radiocarbon reservoir effect in the western Ross Sea}, booktitle = {Annual West Antarctic Ice Sheet Meeting}, year = {2005}, note = {id: 434}, month = {2005}, address = {Sterling, VA}, author = {Hall, Brenda L. and Henderson, Gideon M. and Baroni, Carlo and Kellog, Thomas} }