AGU: Geophysical Research Letters

 

Editors' Highlight

Antarctic Bottom Water has warmed within recent decades

Antarctic Bottom Water (AABW), the coldest and deepest layer of the western South Atlantic, originates in the waters surrounding Antarctica. In the subtropics, most of this current joins water in the Brazil Basin through the Vema Channel, a narrow gorge on the seafloor about 1000 km southeast of Rio de Janeiro. Flow through the Vema Channel has been monitored for the past 35 years, consisting of 94 high-precision, full-depth stations from 19 visits, plus 12 stopovers at two nearby locations. Zenk and Morozov (2007) found that water temperatures in this channel were fairly level before 1992, but that the next 15 years were marked by a warming trend that raised temperatures about 0.0028°C each year. Though this trend is seen, the flow's properties through the Vema Channel were highly variable. Nonetheless, the authors used this long record to conjecture that the AABW also has undergone slight freshening, and noted that further long-term studies on deep circulation and water mass properties may help reveal whether abyssal oceans aside from choke points like the Vema Channel are warming.

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