Spatial and Temporal Variability of Atlantic Water in the Arctic From 40 Years of Observations

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Richards, Alice E., Johnson, Helen L., Lique, Camille
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union (AGU) 2022
• Subjects: Arctic; Arctic Ocean; Sea ice
• Online Access: https://archimer.ifremer.fr/doc/00788/90039/95619.pdf; https://doi.org/10.1029/2021JC018358; https://archimer.ifremer.fr/doc/00788/90039/

Atlantic Water (AW) is the largest reservoir of heat in the Arctic Ocean, isolated from the surface and sea-ice by a strong halocline. In recent years AW shoaling and warming are thought to have had an increased influence on sea-ice in the Eurasian Basin. In this study we analyse 59000 profiles from across the Arctic from the 1970s to 2018 to obtain an observationally-based pan-Arctic picture of the AW layer, and to quantify temporal and spatial changes. The potential temperature maximum of the AW (the AW core) is found to be an easily detectable, and generally effective metric for assessments of AW properties, although temporal trends in AW core properties do not always reflect those of the entire AW layer. The AW core cools and freshens along the AW advection pathway as the AW loses heat and salt through vertical mixing at its upper bound, as well as via likely interaction with cascading shelf flows. In contrast to the Eurasian Basin, where the AW warms (by approximately 0.7 °C between 2002 and 2018) in a pulse-like fashion and has an increased influence on upper ocean heat content, AW in the Canadian Basin cools (by approximately 0.1 °C between 2008 and 2018) and becomes more isolated from the surface due to the intensification of the Beaufort Gyre. These opposing AW trends in the Eurasian and Canadian Basins of the Arctic over the last 40 years suggest that AW in these two regions may evolve differently over the coming decades. Key Points Atlantic Water is evolving in opposing ways in eastern and western sectors Data suggest Atlantic Water cools during transit via vertical mixing at its upper bound and through interaction with cool dense shelf waters Atlantic Water core temperature is generally effective in assessing Atlantic Water heat content but does not always capture temporal trends Plain Language Summary A few hundred meters beneath the surface of the Arctic Ocean lies a warm, salty layer of Atlantic origin, called Atlantic Water (AW), which is isolated from sea-ice and the ocean surface by a vertical ...