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theses

The West Antarctic Peninsula (WAP) has experienced rapid warming over the past several decades, which has resulted in the melting of glaciers and sea ice and created serious consequences for many ice-dependent species. Upper Circumpolar Deep Water (UCDW) is a warm, nutrient-rich water mass found in deep waters off the WAP continental shelf. It is the major source of oceanic heat and nutrients to the shelf waters. This dissertation focuses on the transport of this water mass onto the shelf and its transformation as it moves toward coastal canyons. Data from glider transects along the WAP shelf showed that a significant portion of heat advected onto the shelf is carried in mesoscale eddies. Most of these eddies move across the shelf along the northeastern walls of shelf-incising troughs that open at the shelf break. These mesoscale features steadily lose heat with increasing distance along their paths and may be responsible for as much as 50% of the heat flux onto the shelf. Once on the shelf, UCDW follows complicated pathways toward the coast. Virtual drifters released at several depths near the shelf break in a high-resolution numerical model of the WAP showed that UCDW moves northward along the shelf slope until it is pulled into the shelf interior at one of several troughs. Drifters were often caught in trough-contained cyclonic gyres, moving shoreward along their northern walls and seaward along their southern walls. They entered Palmer Deep, an ecologically important coastal canyon in the northern part of the WAP, primarily from the northeast. Those that traveled the farthest north before entering the canyon cooled most significantly. Results from the model, along with data from a subsurface mooring deployed at the head of a coastal canyon, were used to describe the nearshore circulation at the end of the UCDW transit. Transport was dominated by a southeastward-flowing current during winter and shifted toward the southwest during summer after sea ice had retreated and when northerly wind intensity was strong. More UCDW entered the canyon during winter than summer, which may be the result of a more barotropic flow during winter that more readily follows bathymetric contours. As wind intensity on the WAP increases and sea ice decreases, the amount of ocean heat reaching ice-dependent coastal ecosystems is likely to increase. The results presented here reveal the complexity of circulation on the WAP and the importance of mesoscale observations in understanding these changes.

ETD_8282

Ph.D.

Includes bibliographical references

by NicoleCouto

doi:10.7282/T3N87DW1

ETD doctoral

The author owns the copyright to this work.