Holocene paleoenvironmental reconstruction of the continental shelves adjacent to the Denmark Strait (Iceland)

This dissertation presents four studies linked by the theme of reconstructing North Atlantic Quaternary paleoceanography. Holocene paleoceanographic conditions on the East Greenland and Iceland continental shelves adjacent to the Denmark Strait are assessed in three studies of marine cores. The first presents a high-resolution reconstruction of Holocene paleoceanography based on stable isotopes, sedimentology, and foraminiferal assemblage data from four marine cores. Paleoceanographic reconstructions are presented for the Younger Dryas, Preboreal, Middle Holocene, and Late Holocene. Polar Water is present on both shelves during the Younger Dryas. Conditions during the Preboreal are originally warm, then drastically cool, and gradually rewarm as Atlantic Water flows northward into the Denmark Strait. The Middle Holocene is the warmest interval on both shelves, with ice-free Polar Water in East Greenland and Atlantic Water in Iceland. Neoglacial cooling in the Late Holocene begins ca 5.5 cal ka in East Greenland, at 3 cal ka in North Iceland, and during the last 500 years in southwest Iceland. The cores were sampled at sufficient resolution to discuss millennial-scale variability.; The second marine core study documents three light δ13C events during the Younger Dryas and Early Holocene on the East Greenland shelf, as recorded by benthic and planktic foraminifera. The three events are temporally and spatially transgressive from the outer shelf to the coast. The hypothesized mechanism for the light δ13C is expulsion of methane from gas hydrates in the seafloor from pressure decrease during ice sheet retreat.; The third paleoceanographic reconstruction uses 210Pb geochronology from box cores in three fjords and the shelves adjacent to the Denmark Strait to develop accumulation rates for these environments over the last century. The 210Pb based sediment accumulation rates are compared between the two high-latitude continental shelves and the three fjords in the context of local sedimentary processes, and used to document changes in sedimentation-related processes over the last century.; Lastly, the sensitivity of Northern Hemisphere climate to extreme changes in Arctic sea ice during the Last Glacial Maximum and Holocene is evaluated with an AGCM modelling experiment. The sensitivity experiment demonstrates the vital role of sea ice in modulating climate. The climate, especially in winter and centered around the North Atlantic, is found to be extremely sensitive to sea ice. Thus, accurate paleoceanographic reconstructions are fundamentally important to the paleo-community.