CHARACTERIZING MAJOR ICEBERG SOURCES TO THE NORTH ATLANTIC AND ASSOCIATED BASINS

An important element of ice-ocean-atmosphere interactions and their role in abrupt climate change is the fresh water contributed to the surface ocean by the melting of icebergs. Large fluxes of fresh water reduce surface density and thus impact deep ocean circulation. Additionally, the fresher, colder water resulting from iceberg melting may enhance the formation of sea ice. Provenance studies of the terrigenous fraction of marine sediments provide important constraints on outlet regions of large quantities of icebergs, which drop entrained continental sediments to the ocean floor as they melt. An excellent example is the Heinrich Events of the last glaciation, with a provenance most compatible with origin from the Hudson Strait. However, other important sources of icebergs exist around the North Atlantic, Nordic Seas, and Arctic, as evidenced by large troughs that hosted ice streams. Several of these troughs have massive glacio-marine sediment fans deposited at their mouths, positioned on the continental slope. These trough mouth fans are significant deposits because they highlight other locations where important iceberg armadas might have been launched, and they contain sediment whose provenance signature should be the same as distal sediment deposits. By better defining the character of the sediment within these fans, we hope to increase our ability to identify the contributions of specific ice streams to marine deposits around the region.

As a first step to evaluate the importance of these various ice stream sources to North Atlantic, Nordic Seas and Arctic Ocean ice rafted detritus, we are working to characterize the provenance of sediment in the trough mouth fans in these regions. This study combines spatially associated data sets of continental geology, glacial geology, marine geology and surface currents in order to identify the likely sources and pathways of distinctive iceberg-contributed detritus into the North Atlantic. The eventual goal is a comprehensive trough mouth fans data set, backed by glacial and marine geology, paleoclimate data, and numerical models. This type of information has important implications for studies of millennial variability in the last glaciation as well as for understanding the evolution of ice sheets through the Pleistocene.