GEOSCIENCE SEMINAR - Dr. Anna J. Pieńkowski, Department of Physical Sciences, MacEwan University, Canada; and School of Ocean Sciences, Bangor University, UK:

The late Quaternary evolution of Arctic Canada as an Arctic-Atlantic ocean gateway: the interplay of climate, sea-level, ice, and oceans

20.04.2017 | Lone Davidsen

Dato fre 21 apr
Tid 11:15 12:15
Sted Geoscience auditorium, 1671-137

ABSTRACT:

The late Quaternary evolution of Arctic Canada as an Arctic-Atlantic ocean gateway: the interplay of climate, sea-level, ice, and oceans

Dr. Anna J. Pieńkowski, Department of Physical Sciences, MacEwan University, Canada; and School of Ocean Sciences, Bangor University, UK

At present, the marine channels of the Canadian Arctic Archipelago comprise the second largest gateway for heat and water exchange between the Arctic and Atlantic oceans. Recent multiproxy marine core data, in tandem with geophysical surveys, show a highly dynamic late Quaternary history since the Last Glacial Maximum when grounded Laurentide and Innuitian ice effectively blocked Arctic-Atlantic connections. Deglaciation was marked by rapid marine-based ice retreat under glacio-isostatically elevated sea-level and subsequent major re-ordering of ocean circulation and ecosystem distribution, as suggested by multiproxy core data (sedimentology, micropaleontology, biogeochemistry). Glacio-isostatically enhanced water depths (by >100 m) likely allowed increased penetration of subsurface Atlantic watermasses during the early Holocene, as indicated by planktonic foraminifera (Neogloboquadrina pachyderma) and foraminiferal δ18O. Such heightened oceanic exchange, accompanied by higher solar irradiance, promoted higher ecosystem productivity during reduced seasonal sea-ice (as evidenced by dinocysts, foraminifera, δ13C), potentially corresponding to the terrestrial Holocene Thermal Optimum. Subsequent glacio-isostatic rebound progressively excluded Atlantic-sourced watermasses, establishing essentially “modern” oceanographic conditions by ~7,000 cal yrs BP. This dynamic late Pleistocene-early Holocene history provides valuable analogues for pronounced environmental changes observed over the last few decades in the Arctic-North Atlantic realm (e.g. sea ice decline). To improve our understanding of past and present climate shifts and refine regional (paleo)environmental reconstructions, current research efforts also include the systematic characterization of proxies (micropaleontology, biogeochemistry) in surface sediments relative to measured oceanographic parameters and multiproxy studies of high-resolution sediment records in Arctic to Atlantic Ocean transects.

Forelæsning / foredrag, Institut for Geoscience, Medarbejdere