Date of Award

Summer 1995

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ocean/Earth/Atmos Sciences

Committee Director

Larry P. Atkinson

Committee Member

A. D. Kirwan, Jr.

Committee Member

John M. Klinck

Committee Member

Sydney Levitus

Abstract

Understanding Arctic Ocean circulation may be critical to fully understanding the global oceanic salt and heat cycles and their response to climate variability. This thesis examines how one important aspect of Arctic Ocean circulation, the effect of freshwater inflow, may contribute to the variability of these cycles. The multiple roles that freshwater runoff performs in the Arctic Ocean include: (1) the formation of shelf and basin scale density currents; (2) maintenance of the strong density stratification; (3) control of the thickness and strength of the ice pack; and (4) control of deep convection. Sources and sinks of freshwater in the Arctic include: shoreline discharge as point and non-point runoff; influx through Bering, Fram and/or other straits; permafrost erosion; precipitation; formation and melting of glacial and sea ice shelf mixing and efflux through Fram Strait and the Canadian Archipelago. With newly acquired data, the annual runoff discharge cycle for most of the Arctic rivers for the 50 years up to 1987 and the Bering Strait freshwater flux for the years from 1943 to 1987 have been quantified. For the period 1973 to 1987, where data for most Arctic rivers overlap, the estimated mean annual discharge is 2646 km3$ yr-1 with a standard deviation of 150 km3 yr-1 and a coefficient of variation of 0.06.

Understanding the effect of freshwater inflow is necessary because variation in annual inflow of freshwater to the Arctic could impact deep convection in the northern North Atlantic. The data has been utilized in a numerical model of the Arctic mixed layer to establish a residence time for freshwater in the Arctic and to explain the ambiguity of previous residence times derived from tracer studies. The model results show that the freshwater outflow from the Arctic Ocean is generally insensitive to small observed interannual variations in Arctic freshwater inflow, but that a large enough variation may be a part of the conditions for the production of surface salinity anomalies in the northern North Atlantic.

DOI

10.25777/feyb-tw07

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