Date of Award

Spring 2008

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ocean & Earth Sciences

Program/Concentration

Oceanography

Committee Director

John M. Klinck

Committee Member

Eileen Hofmann

Committee Member

Robin D. Muench

Committee Member

Chester E. Grosch

Committee Member

John A. Adam

Abstract

A mesoscale resolution (5 km) regional ocean model (ROMS), coupled thermodynamically/dynamically to a sea ice model (CICE) and thermodynamically to an ice shelf is used to investigate Ross Sea seasonal sea ice cycle, polynya dynamics, distribution and transformations of continental shelf water masses, and bottom water formation. Daily atmospheric forcing is from the ECMWF ERA-40 dataset, and for a separate simulation, wind forcing for Terra Nova Bay is substituted from daily automatic weather station (AWS) data. Simulated Ross Sea sea ice concentration reproduces the winter lead opening events observed in the SSM/I signal; however, it underestimates open water area (rmsd ∼20%). Timing and advance of the Ross Sea spring-summer polynya are well captured. No local melting takes place during winter and over two years of simulation, heat loss at the ocean surface is offset 90% by lateral oceanic heat flux. Terra Nova Bay cumulatively produces more than twice the sea ice when forced with AWS winds. Forcing the Terra Nova Bay polynya with weaker winds result in continuous erosion of the High Salinity Shelf Water (HSSW) layer over the western Ross Sea continental shelf. Enhanced sea ice production and export driven by realistic winds are required to maintain the northward transport of dense shelf water.

High Salinity Shelf Water (HSSW) is formed in and exported from Terra Nova Bay and Ross Sea polynya areas at 0.14 and 0.64 Sv over two years of simulation. The larger area including the coastal polynya regions in the western Ross Sea provides a 1 Sv HSSW source while the Ross Ice Shelf (RIS) is a sink for about 0.4 Sv. Low Salinity Shelf Water (LSSW) outflow from beneath RIS cavity is 0.60 Sv. Modified Shelf Water (MSW)/Antarctic Bottom Water (AABW) is abundant over the entire continental shelf, forming the anticyclonic cell over the western Ross Sea. MSW/AABW net off-shelf transport and Modified Circumpolar Deep Water (MCDW)/Lower Circumpolar Deep Water (LCDW) net onshelf transport are 2.23 and 0.7 Sv, respectively. Replacing AWS winds with ECMWF ERA-40 winds over the Terra Nova Bay results in larger scale dilution of HSSW in the depressions of the western Ross Sea shelf, diminishes HSSW circulation and transport northward along Victoria Land Coast, disrupts the western gyre, and causes an overall decrease in vertically averaged transport over the western Ross Sea shelf.

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DOI

10.25777/nt39-1n47

ISBN

9780549596776

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Oceanography Commons

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