The Northern Bering Sea: An Ecosystem in Transition
Abstract
Within the past decade, the northern Bering Sea has experienced a rapid reduction of sea ice and warming seawater temperatures both south and north of St. Lawrence Island (SLI). Time series environmental studies indicate significantly faster declines in seasonal sea ice over the last 6 years in comparison to the previous 25 years. The recent loss of sea ice includes an earlier sea ice break-up and later fall freeze-up, both impacted by warming seawater temperatures. The change in sea ice phenology can influence spring ice edge production and associated pelagic-benthic coupling of organic carbon to the underlying sediments. The decline in sea ice has coincided with reduction in the abundance and biomass of the dominant bottom dwelling animals, including clams that are key food for diving sea ducks and walrus, and amphipod prey for gray whales. Where high biomass remains, these prey patches are contracting northward. Time series studies both south and north of SLI are being maintained as part of the Distributed Biological Observatory (DBO), an internationally coordinated effort that is generating seasonal and interannual data to better understand this changing marine ecosystem under ongoing climate change. We will present a case study of the DBO1 stations south of SLI, where water temperatures are influenced by winter sea ice formation, and have been sea ice covered an average of 148 +/-18 days over the 1979-2014 period. By comparison, sea ice coverage over the DBO1 stations declined to 100 days in 2015 and 2016, decreasing to only 80 days in 2017, with lower values in 2018. Notably, during July 2018 the bottom water temperatures south of SLI in the DBO1 region reached the highest values measured in the last 28 years, averaging 1.5 °C in an area where bottom water temperatures typically never exceed 0°C year round. These results suggest a major reduction to the winter polynya formation and consequent reduction in cold bottom water formation. Both the changing seasonality of spring sea ice retreat and associated ice edge production have a dramatic potential to impact pelagic-benthic coupling processes that can have major impacts on the ecosystem structure in the region.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMOS53B..06G
- Keywords:
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- 0738 Ice;
- CRYOSPHEREDE: 0232 Impacts of climate change: ecosystem health;
- GEOHEALTHDE: 4817 Food webs;
- structure;
- and dynamics;
- OCEANOGRAPHY: BIOLOGICAL AND CHEMICALDE: 4215 Climate and interannual variability;
- OCEANOGRAPHY: GENERAL