Accelerated freshening of Antarctic Bottom Water over the last decade in the Southern Indian Ocean

Thumbnail Image
Date
2017-01-25
Authors
Menezes, Viviane V.
Macdonald, Alison M.
Schatzman, Courtney
Linked Authors
Alternative Title
Date Created
Location
DOI
10.1126/sciadv.1601426
Replaced By
Keywords
Salinity
AABW
Changes
Water masses
T-S properties
Iceberg
Calving
Antartica
Abyss
Climate change
Abstract
Southern Ocean abyssal waters, in contact with the atmosphere at their formation sites around Antarctica, not only bring signals of a changing climate with them as they move around the globe but also contribute to that change through heat uptake and sea level rise. A repeat hydrographic line in the Indian sector of the Southern Ocean, occupied three times in the last two decades (1994, 2007, and, most recently, 2016), reveals that Antarctic Bottom Water (AABW) continues to become fresher (0.004 ± 0.001 kg/g decade−1), warmer (0.06° ± 0.01°C decade−1), and less dense (0.011 ± 0.002 kg/m3 decade−1). The most recent observations in the Australian-Antarctic Basin show a particularly striking acceleration in AABW freshening between 2007 and 2016 (0.008 ± 0.001 kg/g decade−1) compared to the 0.002 ± 0.001 kg/g decade−1 seen between 1994 and 2007. Freshening is, in part, responsible for an overall shift of the mean temperature-salinity curve toward lower densities. The marked freshening may be linked to an abrupt iceberg-glacier collision and calving event that occurred in 2010 on the George V/Adélie Land Coast, the main source region of bottom waters for the Australian-Antarctic Basin. Because AABW is a key component of the global overturning circulation, the persistent decrease in bottom water density and the associated increase in steric height that result from continued warming and freshening have important consequences beyond the Southern Indian Ocean.
Description
© The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Science Advances 3 (2017): e1601426, doi:10.1126/sciadv.1601426.
Embargo Date
Citation
Science Advances 3 (2017): e1601426
Cruises
Cruise ID
Cruise DOI
Vessel Name
Except where otherwise noted, this item's license is described as Attribution-NonCommercial 4.0 International