Arctic and Sub‐Arctic Mechanisms Explaining Observed Increasing Northward Flow Through the Bering Strait and Why Models May Be Getting It Wrong

• Published in: Geophysical research letters 2023-12, Vol.50 (24), p.n/a
• Main Authors: Peralta‐Ferriz, Cecilia, Woodgate, Rebecca A.
• Format: Article
• Language: English
• Subjects: Arctic ice; Arctic Ocean change; Bering Strait oceanic flow; Bottom pressure; Datasets; East Siberian Sea; GRACE ocean bottom pressure; Inflow; Modelling; multiyear trends in Pacific inflow; Nutrient content; Nutrient cycles; Nutrients; Ocean bottom; Ocean floor; Ocean models; Oceans; Polar waters; pressure head forcing; Salinity; Salinity effects; Salinization; Satellite data; Satellites; Sea surface; Straits; Summer; Trends; Water flow; Water properties; Wind; Winds
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2023GL104697

The Pacific oceanic input to the Arctic via the Bering Strait (important for western Arctic ice retreat, water properties, and nutrient supply) has been increasing for three decades. Using satellite Ocean Bottom Pressure (OBP) and Dynamic Ocean Topography (DOT) data, we show that long‐term trends in mooring data for a well‐sampled sub‐period (2003–2014) relate to summer OBP and DOT drop in the Arctic's East Siberian Sea (ESS), in turn caused by stronger westward ESS winds, and increased fall westward winds in the Bering Sea. OBP/DOT differences imply strong (0.17 psu/year) ESS salinization, likely caused by hitherto unappreciated increased Pacific inflow to that region. We find ESS OBP trends are (erroneously) reversed in older data versions, and estimate that ESS salinization may significantly mediate Bering Strait flow increase. These facts may explain why models assimilating older OBP data, or with erroneous Bering Strait salinities, fail to simulate observed Bering Strait flow increase. Plain Language Summary Direct year‐round, in‐water measurements show the Pacific oceanic flow to the Arctic (which is only via the narrow Bering Strait) has been increasing for three decades. This flow is important to the region as it triggers seasonal ice retreat in the Pacific side of the Arctic, the “western Arctic,” and strongly influences the temperature, salinity, and nutrient content of western Arctic waters. Using satellite data sets that measure the height of the sea surface, and how it changes, we find we can explain the 2003–2014 observed flow increase by increased westward winds in the Arctic in summer and in the Bering Sea in fall. These satellite data sets also imply parts of the coastal western Arctic have become much saltier over this period, likely due to previously unsuspected increased Pacific input to the region. This increased salinity acts to slow the increasing flow to the Arctic. We find older versions of some of these satellite data sets are inconsistent with the observed flow increase. Most model simulations of the Arctic do not currently capture the observed flow increase. We suggest this may be due to fitting these models to older (erroneous) satellite data sets, or having poor representation of the salinity of Pacific waters. Key Points Satellite data show long‐term Bering Strait flow increase may be due to increasing westward winds in the summer Arctic and fall Bering Sea Data imply large (0.17 psu/year) East Siberian Sea salinization, like