Atlantic Water heat transport variability and trends into the Amerasian Basin: A first look using SODA4

Atlantic Water (AW) inflow plays a central role in Arctic Ocean warming and Atlantification, yet its transport into the Amerasian Basin remains poorly constrained. Using four ocean–sea ice reanalyses, including the new SODA4, we assess the structure, long-term trends, and variability of AW transport. While three of the reanalyses are consistent with prior transport estimates upstream of the Lomonosov Ridge, only SODA4 realistically captures the observed transports into the Amerasian Basin across the Lomonosov Ridge. One of the reanalyses, GLORYS12, significantly underestimates the heat content of Atlantic Water upstream of the Lomonosov Ridge as a result of anomolously high heat loss in the Barents Sea and excess cooling in the Barents Sea. We derive the first 40-year time series of heat transport into the Amerasian Basin. The ensemble mean of this time series shows that AW heat transport has increased by 0.36 TW/year (1984–2016) yielding a 5 ZJ increase in Amerasian Basin heat content. Interannual and interdecadal modes strongly modulate AW heat transport across the Lomonosov Ridge over the 40-year period. The leading mode of variability is associated with the phases of the Arctic Dipole anomaly - an atmospheric climate pattern which modulates the strength of the Siberian and Beaufort high-pressure systems. These results suggest that accurately resolving Atlantic Water structure and transport across the Lomonosov Ridge and in the Barents Sea is essential for accurately characterizing ocean-driven Arctic warming as far east as the Amerasian Basin and Beaufort Gyre.