Abstract
Hydrographic data collected from research cruises, bottom‐anchored moorings, drifting Ice‐Tethered Profilers, and satellite altimetry in the Beaufort Gyre region of the Arctic Ocean document an increase of more than 6,400 km3 of liquid freshwater content from 2003 to 2018: a 40% growth relative to the climatology of the 1970s. This fresh water accumulation is shown to result from persistent anticyclonic atmospheric wind forcing (1997–2018) accompanied by sea ice melt, a wind‐forced redirection of Mackenzie River discharge from predominantly eastward to westward flow, and a contribution of low salinity waters of Pacific Ocean origin via Bering Strait. Despite significant uncertainties in the different observations, this study has demonstrated the synergistic value of having multiple diverse datasets to obtain a more comprehensive understanding of Beaufort Gyre freshwater content variability. For example, Beaufort Gyre Observational System (BGOS) surveys clearly show the interannual increase in freshwater content, but without satellite or Ice‐Tethered Profiler measurements, it is not possible to resolve the seasonal cycle of freshwater content, which in fact is larger than the year‐to‐year variability, or the more subtle interannual variations.
Highlights
The Arctic Ocean freshwater budget is influenced by changes in the intensity of freshwater sources associated with precipitation, including runoff from the land and exchanges with the Pacific and Atlantic Oceans, and processes governing the redistribution of the fresh water under the influence of winds, sea ice conditions, and ocean currents, as well as mixing between waterJournal of Geophysical Research: Oceans masses
Beaufort Gyre Observational System (BGOS) surveys clearly show the interannual increase in freshwater content, but without satellite or Ice‐Tethered Profiler measurements, it is not possible to resolve the seasonal cycle of freshwater content, which is larger than the year‐to‐year variability, or the more subtle interannual variations
The Arctic Ocean freshwater budget is influenced by changes in the intensity of freshwater sources associated with precipitation, including runoff from the land and exchanges with the Pacific and Atlantic Oceans, and processes governing the redistribution of the fresh water under the influence of winds, sea ice conditions, and ocean currents, as well as mixing between water Journal of Geophysical Research: Oceans
Summary
The Arctic Ocean freshwater budget is influenced by changes in the intensity of freshwater sources associated with precipitation, including runoff from the land and exchanges with the Pacific and Atlantic Oceans, and processes governing the redistribution of the fresh water under the influence of winds, sea ice conditions (drift, concentration, and thickness), and ocean currents, as well as mixing between water. Data from the BGOS moorings and Ice‐Tethered Profilers (ITPs; Krishfield et al, 2008; Toole et al, 2011) are analyzed in context with each other and with freshwater content estimates from annual late summer‐hydrographic surveys in order to quantify Beaufort Gyre fresh water accumulation and release at different time scales (amplitudes and mechanisms) and characterize the uncertainties of the different types of measurements analyzed. While each individual data set has its limitations with respect to estimating freshwater content, the analysis of freshwater content changes combined from all of these data sources, together with the results of numerical modeling, provides better understanding of the processes and mechanisms of fresh water accumulation and release in the region.
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