Ocean/Atmosphere Interactions and Trace Metal Geochemistry in Ocean and Sea Ice Sediments.

Abstract

During last glacial period, abrupt climate events were recorded in the Greenland ice core and North Atlantic sediment cores suggest major millennial scale variability in the northern North Atlantic, marked by a series of abrupt climate changes from 60 to 20 ka, first characterized by rapid shifts in the Greenland ice core oxygen isotope record. The use of high-resolution marine sediment cores in regions like the Pacific Ocean that are far afield from the region of climatic forcing allows us to evaluate different mechanisms for transmission of these major climate change events. The subarctic northeastern Pacific Ocean was also influenced by the growth and retreat of the smaller, western side of the North American ice sheet, the Cordilleran Ice Sheet (CIS). In Chapters 2 and 3, I use the δ18Ocalcite and the ratio of Mg/Ca in planktonic foraminifera to reconstruct sea surface temperatures and δ18Oseawater from high-resolution ocean sediment core MD02-2496 offshore of Vancouver Island in the subarctic Northeastern Pacific to reconstruct the effects of ocean temperatures on the marine margin of the CIS during the deglacial. The ice rafted debris record suggests an increase in calving events that coincide with the retreat of the CIS beginning around 17 ka. From 50 to 10 ka, surface ocean temperature and δ18Oseawater are compared with core sites to the south along the California margin, to examining the relative changes in surface ocean characteristics during Dansgaard-Oeschger events. Warm, relatively saline waters dominate offshore during these intervals, perhaps as a result of increased tropical waters from the south advected northward by the relative strengthening of the California Undercurrent. Chapter 4 is a characterization of sediments in modern Arctic sea ice from sites in the northern Canadian Arctic Archipelago and offshore from Point Barrow, AK. Sea ice aggregates sediments entrained during sea ice formation and may therefore contribute to surface ocean Fe concentrations. In Chapter 4, elemental data from sea ice cores collected from shallow coastal regions in the Beaufort/Chukchi Sea and the Canadian Arctic are presented, with the potentially bioavailable pool of filterable and particulate Fe from sea ice sediments in these regions.