IMPACTS OF CLIMATE CHANGE ON LARGE SCALE OCEAN PROCESSES
Stuart Cunningham
National Oceanography Centre, Southampton
Executive Summary
The meridional overturning circulation (MOC) is part of a global ocean circulation that redistributes heat from Equatorial to Polar Regions. In the Atlantic the MOC carries heat northward which is released to the atmosphere and maintains UK temperatures between 5-10°C higher than elsewhere at similar latitudes. However, the present strength and structure of the MOC may not continue: climate models suggest that increasing atmospheric greenhouse gas could lead to an abrupt rearrangement of the MOC and climate models and paleoclimate records indicate that the MOC has undergone large and rapid changes in the past 20,000 years. Recent observational evidence suggests that since the early 1990s the MOC has slowed by up to 30%, with a significant adjustment of ocean water masses. The interpretation of a 30% slowing is controversial because of our lack of understanding of the natural variability of the MOC, and possibly conflicting evidence of warmer North Atlantic sea surface temperatures. There is a broad scientific consensus that continuous observations of the strength and structure of the MOC are required: a UK/US consortium installed a continuous monitoring system in 2004 and the first results are expected in October 2006.
Level of Confidence
Low
Large amount of disagreement between studies and there are limitations to models and observations.
Key Sources of Information
Please acknowledge this document as: Cunningham, S. (2006). Impacts of Climate Change on Large Scale Oceanic Processes in Marine Climate Change Impacts Annual Report Card 2006 (Eds. Buckley, P.J, Dye, S.R. and Baxter, J.M), Online Summary Reports, MCCIP, Lowestoft, www.mccip.org.uk