The Antarctic Peninsula ice sheet since the Last Glacial Maximum
Heroy, David Carlson
Anderson, John B.
Doctor of Philosophy
Antarctic is the coldest, driest, and most poorly understood climate system on the planet. Data within these pages contributes to the understanding of the Antarctic Peninsula region, a global warming "hot spot" roughly the size of the state of Texas. This dissertation has been organized into three chapters; the first chapter addresses the size and configuration of the ice sheet during the Last Glacial Maximum (LGM), an important issue for quantifying post-LGM sea level rise and providing boundary conditions for General Circulation Models. Geomorphic features analyzed in multibeam swath bathymetry and seismic data from the 2002 cruise of the Nathaniel B. Palmer indicate grounded ice that was streaming up to or near (< 10 km landward of) the shelf break. These data greatly expand earlier predictions of the size of the ice sheet during the LGM. The second chapter addresses question, how do ice sheets react to warming and rising seas? This chapter focuses on marine sedimentologic and radiocarbon data. Our findings deglaciation occurred progressively from the outer to the inner continental shelf, as well as from the north to the south. Retreat initiated by ∼ 18,000 to 14,000 calibrated years before present (cal yr BP) from the outer shelf, thousands of years earlier than predicted by numeric models. A significant step in the data occurs at ∼ 14,000 cal yr BP and possibly at ∼ 11,000 cal yr BP, coincidental to rapidly rising sea level (melt water pulses 1a and 1b). This supports the hypothesis that rapidly rising sea level is associated with marine ice sheet destabilization. The third chapter addresses the question, how has the climate changed in the Peninsula region? This is the first study from the Bransfield Basin that extends through the Holocene, recording the variable climate history back to the decoupling of the ice sheet from this mid-shelf region ca. 10,650 cal yr BP. Based on sediment and diatom assemblage analysis, we identify five separate climate regimes, including a significantly shorter Mid-Holocene Climatic Optimum than reported by other studies, from 6,800 to 5,900 cal yr BP.
Geology; Environmental science