Glacial Antarctic warm events as captured by the RICE ice core

• Main Author: Abhijith Ulayottil Venugopal
• Format: Thesis
• Language: unknown
• Published: 2020
• Subjects: Earth sciences; Climate change processes; Climatology; Marine geoscience; Glaciology; RICE ice core; AIM events; Open-ocean convection; Degree Level: Doctoral; Degree Name: Doctor of Philosophy; Degree Discipline: Geology; School: School of Geography; Environment and Earth Sciences; Antarctic; Ross Sea; West Antarctica; Ross Ice Shelf; Greenland; Roosevelt Island; Antarc*; Antarctica; ice core; Ice Shelf; Ice Shelves; NADW; North Atlantic Deep Water; North Atlantic; Sea ice
• Online Access: https://doi.org/10.26686/wgtn.25762587; https://figshare.com/articles/thesis/Glacial_Antarctic_warm_events_as_captured_by_the_RICE_ice_core/25762587

Millennial-scale climatic oscillations have been documented in numerous ice cores in Antarctica and Greenland for the last glacial period. These glacial events, termed Antarctic Isotope Maxima (AIM) and Dansgaard – Oeschger (DO) events in Antarctica and Greenland, respectively, are understood as ocean-mediated mechanisms, with asynchronous progression into warming and cooling. This bipolar seesaw originates from the out-of-phase strengthening and weakening of Antarctic Bottom Water (AABW) and North Atlantic Deep Water (NADW). While proxy records provide strong evidence for enhanced AABW formation during AIM events, the mechanism of its formation during these events remains indiscernible. The process of AABW formation, however, is likely to be different from today. In modern times, AABW formation occurs in front of ice-shelves, whereas during glacial periods, the ice sheets extended to the continental shelf, and the ice-shelves were absent. Ice cores allow the reconstruction of an array of environmental conditions. Here, we present new data from a high-resolution coastal ice core record that sensitively captures changes in temperature, sea ice conditions, primary productivity, and atmospheric circulation pattern. The new data provide important insights into the drivers of AIM events, AABW formation, and the evolution of the bipolar seesaw. This thesis focuses on the high resolution record of major ions bracketing 26-40 kilo year (ka) Before Present (BP), from Roosevelt Island, West Antarctica. Roosevelt Island is a grounded ice rise, located in the north-east of Ross Ice Shelf, in the Southern Ross Sea. The ice core was drilled to bedrock at 764m, as a part of the Roosevelt Island Climate Evolution (RICE) project. The record has been dated to 753m which captures the past 83 ka BP. The major ion record comprises of concentrations of sodium, magnesium, calcium, potassium, chloride, sulphate, nitrate, and Methane Sulphonic Acid (MSA), with an average resolution of ~25 years. We demonstrate that the RICE MSA, sea ...