LATE QUATERNARY CLAY MINERAL AND IRON OXIDE DISTRIBUTIONS ON THE BERING AND CHUKCHI SEA SHELVES: A PROXY FOR OCEAN CIRCULATION THROUGH THE BERING STRAIT

The Southern Ocean wind strength, in conjunction with an open Bering Strait, alters the North Atlantic Meriodional Overturning Circulation (AMOC) controlling the strength and flow direction through Bering Strait (De Boer & Nof, 2004 and Sandal & Nof, 2008). They postulate that the fresher Pacific water altering of AMOC resulted in the Quaternary climatic oscillations known as the Heinrich and Dansgaard–Oeschger (D/O) events.

In the Arctic, clay minerals and iron oxides provide good proxies for provenance and thus, ocean circulation (Ortiz et. al. 2009). To determine the regional clay and iron oxide distribution and thus provide physical evidence of fresh water influx and flow strength into the Arctic Ocean, we measured diffuse spectra reflectance (DSR), on archived grab samples and core tops from several oceanographic expeditions. Varimax-rotated, principal component analysis and Kriging, were used to map the sediment lithology.

Varimax-rotated, principal components analysis (PCA) identified four leading modes that accounts for sediment lithology in both surface and down core samples from our study sites. These spectral modes where then matched to clay mineral and iron oxide spectral standards to determine the mineral assemblages responsible for each of the modes. The modes responsible for the PCA trends are Chlorite + muscovite; Hematite + goethite + illite; smectite + dolomite; and illite + chlorite + chlorophyll a. These results are largly consistent with the previous XRD work of Naidu and Mowatt (1983) and Kalinenko (2001). Kriging of the spatial patterns associated with the different DSR modes allows us to see how the downcore patterns vary geographically in surficial sediment. This enables comparison with the surface maps of Naidu and Mowatt (1983) and Kalinenko (2001). Consistent with the finding of the earlier XRD work, the Chlorite + muscovite assemblage has maximal values in the western North Pacific, while the Hematite + goethite + illite assemblage has maximal values in the Arctic. The smectite + dolomite assemblage reaches maximal values in the Eastern North Pacific and northern Alaska shelf, while the illite + chlorite + chlorophyll a assemblage indicates a productive mixing zone between the North Pacific and Arctic in the vicinity of Bering Strait.