Late Holocene changes in sea-surface conditions in the North Water Polynya, northern Baffin Bay, using organic-walled dinoflagellate cysts

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University of New Brunswick


The North Water (NOW) polynya, located in northern Baffin Bay, is the largest recurrent polynya in the Arctic. This area of open water or low sea-ice concentrations in a region otherwise characterized by high sea-ice concentrations fosters primary production that helps sustain a large and diverse food web and provides resources to the surrounding human communities. The NOW owes its formation to i) the presence of ice arches in Nares Strait that define its northern boundary, ii) strong northerly winds that blow newly formed sea ice southward out of the polynya region, and iii) the upwelling of relatively warm water masses. Due to recent climate warming and Arctic amplification, the factors promoting the formation of the polynya are changing rapidly. This is notably evident from the recent observed instability of the Nares Strait ice arches. This thesis aims to understand the long-term sea-surface variability of the NOW polynya using dinoflagellate cyst (dinocyst) assemblages from a marine record spanning the last ca. 3800 years, and also comparesthe natural variability of the polynya’s dinocyst composition and fluxes to recent (last ca. 60 years) changes. Our results infer relatively gradual changes to the NOW polynya between ca. 3800 and 156 years BP associated with a general sea-surface cooling trend. However, between ca. 1965 and 2015 there is a shift to higher contributions of autotrophic taxa and one to two orders of magnitude higher dinoflagellate cyst fluxes, suggesting a rapid shift to more stratified and open water conditions as a result of increased cryospheric melt associated with Arctic amplification. Climate projections in the Arctic indicate continued cryospheric melt into the future, which will continue to impact the polynya and its formation factors, likely leading to a seasonally open gateway between the Artic and northern Baffin Bay.