@article {2519, title = {Amino acid ratios in reworked marine bivalve shells constrain Greenland Ice Sheet history during the Holocene}, journal = {Geology}, volume = {42}, year = {2014}, month = {Jan-01-2014}, pages = {75 - 78}, abstract = {Reconstructions of ice sheet fluctuations during the Holocene, which encompassed cooler and warmer conditions than those that are captured in the historic record, help to elucidate ice margin sensitivity to climate change. We used amino acid geochronology to constrain the history of the western Greenland Ice Sheet margin during intervals of relative warmth in the middle Holocene. We measured the extent of amino acid racemization in 251 ice sheet-reworked marine bivalve shells from three locations spanning western Greenland. A significant relationship between shell age and the ratio of aspartic acid (Asp) isomers (Asp D/L) was revealed using Bayesian model fitting on 20 radiocarbon-dated shell fragments. The range of Asp-inferred bivalve ages at each site corresponds well with independent records of early Holocene ice retreat and late Holocene ice advance. Furthermore, the frequency of Asp-inferred bivalve ages from the three widely separated locations is nearly identical, with most ages between 5 and 3 ka, coinciding with optimum oceanic conditions. Because ice margin changes in western Greenland are tightly linked with oceanographic conditions, the distribution of reworked bivalve ages provides important information about relative ice margin position during smaller-than-present ice sheet configurations. This approach adds a new chronometer to our toolkit for constraining smaller-than-present ice sheet configurations and may have wide applicability around Greenland. Amino acid ratios in reworked marine bivalve shells constrain Greenland Ice Sheet history during the Holocene. Available from: https://www.researchgate.net/publication/270688646_Amino_acid_ratios_in_reworked_marine_bivalve_shells_constrain_Greenland_Ice_Sheet_history_during_the_Holocene [accessed Jun 5, 2017].}, issn = {0091-7613}, doi = {10.1130/G34843.1}, url = {http://geology.gsapubs.org/cgi/doi/10.1130/G34843.1}, author = {Briner, J. P. and Kaufman, D. S. and Bennike, O. and Kosnik, M. A.} } @article {2525, title = {Response of Jakobshavn Isbrae, Greenland, to Holocene climate change}, journal = {Geology}, volume = {39}, year = {2011}, month = {Jan-02-2011}, pages = {131 - 134}, abstract = {Rapid fluctuations in the velocity of Greenland Ice Sheet (GIS) outlet glaciers over the past decade have made it difficult to extrapolate ice-sheet change into the future. This significant short-term variability highlights the need for geologic records of preinstrumental GIS margin fluctuations in order to better predict future GIS response to climate change. Using 10Be surface exposure ages and radiocarbon-dated lake sediments, we constructed a detailed chronology of ice-margin fluctuations over the past 10 k.y. for Jakobshavn Isbr{\ae}, Greenland{\textquoteright}s largest outlet glacier. In addition, we present new estimates of corresponding local temperature changes using a continuous record of insect (Chironomidae) remains preserved in lake sediments. We find that following an early Holocene advance just prior to 8 ka, Jakobshavn Isbr{\ae} retreated rapidly at a rate of \~{}100 m yr-1, likely in response to increasing regional and local temperatures. Ice remained behind its present margin for \~{}7 k.y. during a warm period in the middle Holocene with sustained temperatures \~{}2 {\textdegree}C warmer than today, then the land-based margin advanced at least 2{\textendash}4 km between A.D. 1500{\textendash}1640 and A.D. 1850. The ice margin near Jakobshavn thus underwent large and rapid adjustments in response to relatively modest centennial-scale Holocene temperature changes, which may foreshadow GIS response to future warming.}, issn = {0091-7613}, doi = {10.1130/G31399.1}, url = {http://geology.gsapubs.org/cgi/doi/10.1130/G31399.1}, author = {Young, N. E. and Briner, J. P. and Stewart, H. A. M. and Axford, Y. and Csatho, B. and Rood, D. H. and Finkel, R. C.} } @article {408, title = {Pleistocene glacial history of the southern Ahklun Mountains, southwestern Alaska: Soil-development, morphometric, and radiocarbon constraints}, journal = {Quaternary Science Reviews}, volume = {20}, year = {2001}, note = {id: 1204}, pages = {353-370}, abstract = {Four new AMS ages, glacial mapping, and measurements of soil development, loess thickness, and moraine morphology constrain the age and extent of at least three Quaternary advances by outlet lobes of an ice cap over the Ahklun Mountains of southwestern Alaska. The relative-age data are from 107 sites correlated to 25 ice-marginal positions in the Kanektok, Goodnews, Togiak, and Kulukak River valleys and along the southeastern flank of the range. Radiocarbon ages provide minimum ages for six {\textemdash} and a maximum age for one {\textemdash} of the former ice margins. Soil and morphometric parameters subdivide the ice limits into three relative-age groups. One to three pre-Wisconsin advances, probably middle Pleistocene in age, are represented by drift with relatively thick B horizons (60{\textpm}5 cm, with Bt horizons), thick loess caps (80{\textpm}12 cm), and broad moraines (135{\textpm}134 m) with gentle side slopes (7{\textpm}5{\textdegree}). An extensive early Wisconsin (sensu lato, s.l.) advance, >39.9 ka, and three associated stillstands or readvances are characterized by intermediate soil and morphometric parameters (Bw and weak Bt horizons with thicknesses of 40{\textpm}11 cm; loess thicknesses of 69{\textpm}46 cm; crest widths of 38{\textpm}13 m; and slope angles of 14{\textpm}4{\textdegree}). The maximum late Wisconsin advance, >16.9 ka, and two readvances or stillstands are associated with thin (20{\textpm}5 cm), weakly to moderately developed Bw horizons, thin loess caps (28{\textpm}8 cm), narrow crest widths (28{\textpm}9 m), and steep slope angles (18{\textpm}3{\textdegree}). The data confirm that early-Wisconsin glaciers in southeast Beringia were much more extensive than late Wisconsin glaciers, which were apparently limited by availability of moisture.}, doi = {10.1016/S0277-3791(00)00111-6}, author = {Manley, W. F. and Kaufman, D. S. and Briner, J. P.} }