ROGER REVELLE COMMEMORATIVE LECTURE. Overturning Assumptions: Past, Present, and Future Concerns about the Ocean’s Circulation

Abstract

In 1800, Count Rumford ascertained the ocean’s meridional overturning circulation from a single profile of ocean temperature constructed with the use of a rope, a wooden bucket, and a rudimentary thermometer. Over two centuries later, arrays of gliders, floats, and moorings are deployed across the span of the North Atlantic to measure the overturning circulation and its spatial and temporal variability. While Rumford appreciated the role the ocean’s overturning plays in redistributing heat, today we understand its crucial role in sequestering anthropogenic carbon dioxide in the deep ocean. What we don’t understand, however, are the mechanisms that control overturning strength and how and why the overturning will change in the decades ahead. This information is crucial to our understanding of the climate system because the extent to which the ocean will continue to be a heat and carbon reservoir depends on the strength of the overturning. Although we have reasons to reject the popularized ocean conveyor belt as a paradigm for the overturning, oceanographers are just now piecing together the complex flow patterns that carry warm waters poleward and cold water equatorward. As the pieces come together, some long-held assumptions are being overturned, and some new paradigms are surfacing.

Keywords

• ocean circulation
• North Atlantic
• ocean heat
• ocean conveyor belt
• overturning circulation