The Role of Arctic Sea Ice Decline on a Changing Freshwater Budget

• Main Author: Ford, Victoria Lauren
• Other Authors: Frauenfeld, Oliver, Bombardi, Rodrigo, Roark, Brendan, Orsi, Alejandro
• Format: Thesis
• Language: English
• Published: 2023
• Subjects: Arctic sea ice; freshwater budget; Arctic; Arctic Ocean; Sea ice
• Online Access: https://hdl.handle.net/1969.1/197873

As one of the most visible aspects of the Arctic Ocean, the sea ice cover is a climatically important buffer between the warm ocean and comparatively cooler atmosphere. However, sea ice is drastically shrinking in all seasons due to a warming climate. This dissertation answers: How does the decline of the ice cover influence recent changes in the Arctic freshwater balance and which key physical mechanisms are responsible? While changes in extent and concentration are common indicators of ice decline, ice thickness changes may be even more important. Transitioning from a perennial to seasonal cover, sea ice approaches a threshold of 0.40-0.50m where ice is thin enough to conduct significant changes to the atmosphere, effectively negating its buffering effect in those regions. Using model simulations, this threshold is applied to historical observations to report 4-14% of the total ice area is overestimated in regions that do not effectively insulate the atmosphere from the ocean. With a reduced ice cover, a greater area of open ocean becomes more conducive to evaporation, by increasing locally sourced precipitation through precipitation recycling. Arctic precipitation transitioned in the 1990s from a primarily remote to a locally-derived moisture source at +1.3% per decade. This change is driven by an east-west pattern, indicating the importance of regionally-specific ice loss and increased evaporation. Solid and liquid Arctic freshwater storage have changed over recent decades but the physical drivers and the contribution of natural variability is still uncertain. Using a spatial pattern matching technique in a coupled climate model large ensemble, internal variability from sea level pressure variations over the Arctic Ocean is found to account for only 7.4% of the total historical trend, confirming that anthropogenic forcing plays a dominant role in driving historical liquid storage change. The novel contributions of this dissertation are thus that it quantifies three key Arctic freshwater-climate linkages: a ...