Correlation between Synthetic Aperture Radar Surface Winds and Deep Water Velocity in the Amundsen Sea, Antarctica

Gisela Carvajal,Lars Ulander,Leif Eriksson,Anna Wåhlin

doi:10.3390/rs5084088

Abstract

The recent observed thinning of the glacier ice shelves in the Amundsen Sea (Antarctica) has been attributed to warm deep currents, possibly induced by along-coast winds in the vicinity of the glacial ice sheet. Here, high resolution maps of wind fields derived from Synthetic Aperture Radar (SAR) data have been studied and correlated with subsurface measurements of the deep water velocities in the Amundsen Sea area. Focus is on periods with low ice coverage in 2010 and 2011. In 2010, which had comparatively low ice coverage, the results indicate a more rapid response to wind forcing in the deep currents than in 2011. The SAR wind speed maps have better spatial resolution than available reanalysis data, and higher maximum correlation was obtained with SAR data than with reanalysis data despite the lower temporal resolution. The maximum correlation was R = 0.71, in a direction that is consistent with wind-driven Ekman theory. This is significantly larger than in previous studies. The larger correlation could be due to the better spatial resolution or the restriction to months with minimum ice coverage. The results indicate that SAR is a useful complement to infer the subsurface variability of the ocean circulation in remote areas in polar oceans.

Highlights

The Amundsen Sea is a seasonally ice-covered shelf sea on the West Coast of Antarctica
The observed current in the mooring is indicated as a red arrow, and it is oppositely directed to the Ekman transport on 3 April
This paper presents the temporal and spatial correlation between the wind field and the current velocity in one of the deep troughs leading from the shelf break to the glaciers in the Amundsen Sea

Summary

Introduction

The Amundsen Sea is a seasonally ice-covered shelf sea on the West Coast of Antarctica. The main reason for their decline appears to be flow of warm dense water onto the shelf, channeled by bathymetric troughs leading to the deep inner basins This has been observed on the Marguerite Trough [5,6,7] and on the Amundsen Shelf [8,9,10]. Field studies in the Amundsen Sea [13] indicate that eastward winds along the shelf break force a deep current toward the ice shelves in the submarine trough. Such a response is in accordance with standard wind-driven Ekman theory [14]: Because of the Earth’s rotation, the wind forces a surface flow directed to the left of the wind direction in the Southern Hemisphere (see Figure 1)

Methods

Results

Conclusion