Marine sediment record from the East Antarctic margin reveals dynamics of ice sheet recession

Abstract

The Antarctic shelf is traversed by large-scale troughs developed by glacial erosion. Swath bathymetric, lithologic, and chronologic data from jumbo piston cores from four sites along the East Antarctic margin (Iceberg Alley, the Nielsen Basin, the Svenner Channel, and the Mertz-Ninnis Trough) are used to demonstrate that these cross-shelf features controlled development of calving bay reentrants in the Antarctic ice sheet during deglaciation. At all sites except the Mertz-Ninnis Trough, the transition between the Last Glacial Maximum and the Holocene is characterized by varved couplets deposited during a short interval of extremely high primary productivity in a fjordlike setting. Nearly monospecific layers of the diatom Chaetoceros alternate with slightly more terrigenous layers containing a mixed diatom assemblage. We propose that springtime diatom blooms dominated by Chaetoceros were generated within well-stratified and restricted surface waters of calving bays that were influenced by the input of iron-rich meltwater. Intervening post-bloom summer-fall laminae were formed through the downward flux of terrigenous material sourced from melting glacial ice combined with mixed diatom assemblages. Radiocarbon-based chronologies that constrain the timing of deposition of the varved sediments within calving bay reentrants along the East Antarctic margin place deglaciation between ca. 10,500-11,500 cal yr B.P., postdating Meltwater Pulse 1A (14,200 cal yr B.P.

On the origins of Earth rotation anomalies: New insights on the basis of both “paleogeodetic” data and Gravity Recovery and Climate Experiment (GRACE) data

“…An interesting and important characteristic of the ICE-5G (VM2) model is that the deglaciation of Antarctica is such that the continent is assumed not to lose mass until the onset of meltwater pulse 1b, a pulse defined by a period of rapidly increasing sea level recorded in the Barbados data set that occurs at the end of the Younger Dryas period. This aspect of the ICE-5G reconstruction has recently been confirmed by Domack et al [2005] and Leventer et al [2006], who have carefully dated the timing of the recommencement of marine shelf sedimentation that occurred as the Antarctic ice sheet pulled back from the shelf break in response to the rise in sea level that was driven by the melting of northern hemisphere land ice. The spatial distribution of continental ice sheet thickness as a function of time for the ICE-5G (VM2) v1.2 model is currently available to interested users at http://www.atmosp.physics.utoronto.ca/ $peltier/data.php…”

Diatom evidence for the onset of Pliocene cooling from AND-1B, McMurdo Sound, Antarctica

“…This fast-growing genus, indicative of high primary productivity at shallow depths, often dominates spring blooms in nutrient-replete environments such as coastal upwelling zones (Kemp et al, 2000). In the Antarctic, intense spring blooms of vegetative Chaetoceros are associated with stable, meltstratified surface waters (Leventer, 1991;Crosta et al, 1997Crosta et al, , 2008Leventer et al, 2006), where lowlight conditions through winter and capping by winter sea ice allow remineralized macronutrients to accumulate in the upper water column (Sweeney, 2003) and bioavailable iron may sometimes accumulate on the ice surface (e.g., Sedwick and DiTullio, 1997). Melt-induced spring blooms conclude when nutrient depletion triggers resting spore formation (Holm-Hansen and Mitchell, 1991); these spores are efficiently exported and preserved in Antarctic sediments.…”

“…Both resting spores and vegetative cells are more commonly associated with pack ice than with fast ice (Ligowski et al, 1992;Scott et al, 1994). Although the value of tying resting spore morphologies to their vegetative counterparts is widely recognized (e.g., Suto, 2006 and references therein), they are currently lumped without species designation in bothmodern and paleoenvironmental investigations (Leventer et al, 1993(Leventer et al, , 2006Crosta et al, 1997Crosta et al, , 2008Armand et al, 2005;Stickley et al, 2005;Esper et al, 2010).…”

Landscape evolution of Antarctica

“…Outlet glaciers thicken and advance seaward in response to a lowering of sea level in the Northern Hemisphere, as demonstrated in the case of the outlets flowing through the Transantarctic Mountains (Denton et al, 1989). Slight thickening occurs in Mac Robertson Land (Mackintosh et al, 2007), but the ice does not extend far offshore (O'Brien et al, 2001;Leventer et al, 2006). In agreement with such a limited expansion, the coastal oases of the Bunger Hills and the Larsemann Hills appear to have remained ice-free during the last glacial cycle Hodgson et al, 2001).…”