Sarah B. Hall

Date of Award

Fall 2022

Document Type

Open Access Dissertation


Earth and Ocean Sciences

First Advisor

Subrahmanyam Bulusu


Salinity is the primary determinant of the Arctic Ocean’s vertical density stratification in the upper ocean, which has major implications on the ocean’s physical dynamics alongside a period of rapidly declining sea ice. In recent decades, the Arctic’s freshwater content (FWC) has increased as a result of the accumulation of freshwater source inputs. Additional freshwater exported to the North Atlantic may hinder overturning processes that are vital to the regulation of global climate. This dissertation employs in situ measurements, satellite observations, and ocean model simulations to better understand salinity and freshwater changes in the Arctic Ocean during this changing climate.

This work first explores surface freshwater flux through major Arctic straits with emphasis on years of high and low sea ice extent. The lowest sea ice extent on record occurred during September 2012 (~3.41 million km2 ) and showed the greatest export to the Atlantic Ocean. Between 2010–2018, export through the Fram Strait strengthened. Next, this dissertation focuses on the Beaufort Gyre, a predominantly anticyclonic circulation system that contains roughly 25% of the Arctic’s FWC, to delineate the discrepancies between salinity products. Most of the models and reanalysis products analyzed in this work overestimate salinity within the first 50 m when compared to in situ measurements, with the exception of ORAS5 (-0.052 bias at 5 m) and MIZMAS (0.105 bias at 5 m). This study reveals that the Russian Shelf makes up ~16% of total FWC in the Arctic Ocean with a trend of -15.63 km3 /year between 1979–2018, driven by Kara and Laptev sea negative trends. A notable regime shift occurred during the summer of 2007, where an anomalous FWC decrease (increase) occurred over the Russian Shelf (Beaufort Gyre), which further suggests that neglecting the Russian Shelf creates an error of 25% in assessing Arctic Ocean FWC change during this 2007 regime transition. These results highlight the drawbacks and advantages of utilizing ocean model simulations for a comprehensive understanding of the Arctic Ocean’s physical dynamics. This dissertation emphasizes the importance of continued observations and refining the accuracy of ocean models as polar regions become more susceptible to climate change.

Included in

Oceanography Commons