Salinity and Temperature Regimes in Eastern Alaskan Beaufort Sea Lagoons in Relation to Source Water Contributions
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Shallow estuarine lagoons characterize >70 % of the eastern Alaskan Beaufort Sea coastline and, like temperate and tropical lagoons, support diverse and productive biological communities. These lagoons experience large variations in temperature (−2 to 14 °C) and salinity (0 to >45) throughout the year. Unlike lower latitude coastal systems, transitions between seasons are physically extreme and event-driven. On Arctic coastlines, a brief summer open-water period is followed by a 9-month ice-covered period that concludes with a late-spring sea ice breakup and intense freshwater run-off. From 2011 to 2014, we examined interannual variations in water column physical structure (temperature, salinity, and δ18O) in five lagoons that differ with respect to their degree of exchange with adjacent marine waters and magnitude of freshwater inputs. Temperature, salinity, and source water composition (calculated using a salinity and δ18O mixing model) were variable in space and time. During sea ice breakup in June, water column δ18O and salinity measurements showed that low salinity waters originated from meteoric inputs (50–80 %; which include river inputs and direct precipitation) and sea ice melt (18–51 %). Following breakup, polar marine waters became prevalent within a mixed water column over the summer open-water period within all five lagoons (26–63 %). At the peak of ice-cover extent and thickness in April, marine water sources dominated (75–87 %) and hypersaline conditions developed in some lagoons. Seasonal runoff dynamics and differences in lagoon geomorphology (i.e., connectivity to the Beaufort Sea) are considered key potential drivers of observed salinity and source water variations.
KeywordsBeaufort Sea Coastal lagoons Temperature Salinity Oxygen isotopes
The authors thank the Captains (T. Dunton and J. Dunton) of the R/V Proteus for their invaluable navigation skills and support of our research. We are also very grateful to field assistants R. Thompson, S. Linn, S. Smith, and J. Smith for their long hours and enthusiastic support of this work. This field-intensive campaign would not have been possible without the support of D. Payer and others at the Arctic National Wildlife Refuge and at US Fish and Wildlife Service headquarters in Fairbanks. We would also like to thank K. Jackson (Texas based logistic support), S. Schonberg (assistance with ArcGIS), and M. Otter at the Marine Biological Laboratory (oxygen isotope analysis). Funding for this work was provided by the National Science Foundation under grant ARC-1023582.
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