Letter abstract

Nature Geoscience 1, 165 - 168 (2008)
Published online: 10 February 2008 | doi:10.1038/ngeo126

Subject Categories: Climate science | Oceanography

Mass and volume transport variability in an eddy-filled ocean

Carl Wunsch


The possibility that the oceanic general circulation is undergoing changes as part, or the cause, of major climate shifts is being intensely discussed1, with some published results relying on data from moorings spanning the North Atlantic Ocean2, 3. The circulation is, however, extremely noisy. Here, I use existing estimates of the frequency and wavenumber content of geostrophic eddies in the ocean4 to show that variations in ocean-wide integrated transport must appear even in the absence of a true long-term trend. Expected fluctuations exceed plusminus20times109 kg s-1 (or plusminus20times106 m3 s-1) and exhibit multi-year timescales. Existing knowledge of the eddy field allows predictions of observed variability and produces lower bounds on the (multi-decadal) timescale required to detect true trends of a large magnitude. Detecting and understanding the effect of climate change on the ocean circulation requires observations in three dimensions over long periods of time.

  1. Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

Correspondence to: Carl Wunsch e-mail: cwunsch@mit.edu


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