The Holocene History of Drift Ice at the Present-Day Limits Off North Iceland and the Eastern Canadian Margin

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This award uses funds to collect and analyze data on quartz and dolomite mineral concentrations and fluxes in a series of sites around Iceland, east Greenland, and the Labrador shelf, with the goal of examining the Holocene spatial and temporal variability of these specific mineral species as measures of drift ice presence or absence and severity. Variations in the extent and duration of drift ice (i.e., icebergs plus various forms of sea ice) in the marginal Seas of the North Atlantic (the Greenland and Iceland Seas, and Baffin Bay/Labrador Sea) influence the climate of adjacent land areas and whose effects can be propagated downstream by both atmospheric and ocean circulation. Reconstructions of variations in the delivery of IRD (ice-rafted debris) to sites in the North Atlantic (based on counts of hematite-stained quartz sand grains) show an overall decrease in IRD from 12,000 years ago to the present, with a series of oscillations spaced at ~1,500 year intervals. In contrast, the IRD on the glacial fraction from sites on the east Greenland shelf show a mid-Holocene interval of little IRD followed by a strong increase during the last 5,000-6,000 years.Initial results suggest that the generally accepted paradigm that Holocene IRD in the North Atlantic region is captured in hematite-stained quartz variations, dominated by a 1,500-yr periodicity, is not correct and that mechanisms other than drift ice are required to explain the pervasive signal. The research will help solve a puzzle of sorts as to why marine sites in the North Atlantic differ in their signal of sedimentological response to climate variability. The research strategy posses strong international collaborations between scientists in the United States, Canada, Norway, and Germany.