REGIONAL PREFERENCES IN THE SEASONAL AND MULTIDECADAL LOSS OF ARCTIC SEA ICE: THE ROLE OF CONTINENTAL RUNOFF

Abstract

Arctic sea ice is of great importance as both a key indicator and a driver of climate change. Sea ice is highly sensitive to temperature changes of the overlying atmosphere and the underlying ocean. The declining trend of Arctic sea ice, especially in late summer when seasonal ice extent is also a minimum, is widely considered a key indicator of the global warming of the planet. This dissertation finds that the observed trends in late summer Arctic sea ice are greatly impacted by natural decadal-to-multidecadal climate variability, mainly by sea surface temperature variability in the Atlantic and Pacific Oceans. The Atlantic Multidecadal Oscillation and Pacific Decadal Variability – via a Pan Pacific mode – each contribute a loss of 3-4% of sea ice concentration (SIC) per decade to the overall loss of 24% per decade since 1979.To better understand the mechanisms driving these trends, the impact of decadal and multidecadal climate variability on the Arctic atmosphere, ocean, and continental hydrology is investigated. Multidecadal climate variability leads to regional and seasonal impacts on atmospheric circulation, ocean heat content, and ocean salinity that vary across the Arctic. Modification of the atmospheric circulation on decadal and multidecadal time scales impacts warm inflow into the Arctic from the North Atlantic and North Pacific, and also leads to redistribution of sea ice in the Arctic. Vertical profiles of ocean temperature and salinity near the mouth of the Arctic rivers provides a means to investigate the impact of variability in continental hydrology on the Arctic marginal seas through the input of freshwater and heat. In the Beaufort Sea, the Atlantic Multidecadal Oscillation leads to increased ocean temperatures and decreased ocean salinity at the mouth of the Mackenzie River, corresponding in time to the annual June peak in river discharge. Finally, the impact of Mackenzie River discharge variability on the freshwater content, temperatures, and SIC in the Beaufort Sea is assessed.