Date of Award

2019

Degree Type

Thesis

Degree Name

Master of Science in Oceanography

Specialization

Physical Oceanography

Department

Oceanography

First Advisor

Kathleen Donohue

Abstract

The West Greenland Current System (WGCS) is a narrow boundary current which en- ters the Labrador Sea from the southeast and flows northward along the west Greenland coast. As part of the cyclonic circulation within the basin, it has recently received atten- tion due to its contribution to Labrador Sea Water (LSW), having been observed with surface drifters, satellite altimetry, and synoptic hydrographic measurements. Direct velocity measurements, especially in the winter months, have been sparse, and there are few previous papers that look at the continuity between the East and West Greenland Current Systems. Additionally, while evidence has been found for a correlation between Labrador Sea processes and North Atlantic Oscillation (NAO), it is still unclear whether this correlation extends to current strength and if so whether it is the same correlation found east of Greenland.

This study makes use of an acoustic Doppler current profiler (ADCP) mounted on the hull of the container ship Nuka Arctica. Every three weeks, the ship crosses between Denmark and Greenland via the Irminger Sea before rounding Cape Farewell and continuing north along the Greenland coast. Two ADCP systems have operated: a 150 kHz ADCP providing measurements to 400 m depth from 1999-2002, and a 75 kHz ADCP providing measurements to 800m depth from 2012-2016. During these periods, there were two years with a negative winter NAO and 3-4 years of wintertime measurements. Here, transport and velocities over 400 meters depth are compared at six current cross sections including one in the EGCS. Transport in the WGCS is found to be up to 1.6 Sv lower in the EGCS, indicating deflection off of Eirik Ridge. Winter transport is generally higher than summer with a more pronounced difference in the EGCS. Similarly, with a 6-18 month lag, a negative NAO phase corresponds to a lower transport in the EGCS. The relationship between the NAO and the WGCS is not clear.

Available for download on Friday, June 05, 2020

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