IMPACTS OF CLIMATE CHANGE ON SEA TEMPERATURE
Robert Marsh and Elizabeth Kent
National Oceanography Centre, Southampton
Supporting Evidence
Measurements of SST are obtained from many different sources. While ocean-based instruments provide the ultimate “ground truth”, satellite-based sensors observe SST in almost real time. The NOAA/NASA Pathfinder SST product (see http://podaac.jpl.nasa.gov/sst/) provides high-resolution datasets from 1985 to 2004 and we can supplement these with data from the Advanced Microwave Scanning Radiometer (AMSR-E), a passive microwave instrument providing SST observations through non-raining cloud (see http://www.remss.com/amsr). To comment on the large-scale Atlantic changes, we also use output from a simulation of the Ocean Circulation and Climate Advanced Model (OCCAM, see Marsh et al., 2005). In addition to satellite and model datasets, blended and ship-based SST products are also available. The NOC dataset, used to comment on UK coastal changes, is derived from Voluntary Observing Ship reports in the International Comprehensive Ocean-Atmosphere Data Set (ICOADS, Worley et al., 2005), on a global 1° x 1° grid at daily time intervals up to the end of 2004 (Kent and Berry, 2005). Combined satellite and non-satellite based data are also collated and updated monthly, in the form of HadISST (see http://www.hadobs.org/). This dataset is widely used in climate studies. Monthly SST anomalies in the OCCAM, AMSR-E and NOC data reported here are in general significantly correlated with HadISST (Marsh et al., 2006).
Compared to other oceans, the Atlantic sector appears to be warming the most dramatically, accounting for 53% of World Ocean warming from 1955-98. Most warming has occurred in the upper 700m in the North Atlantic (Levitus et al., 2005), but this has not been completely linear (for example, up to the early 1970s, some negative heat content anomalies were visible). Nonetheless, the recent heat content anomaly has tended to be positive, and particularly rapid warming since the 1980s is evident, focused over the tropics and mid-latitudes (Marsh et al., 2006). The introduction, in the late 1990s, of ‘Argo’ floats (see http://www.argo.ucsd.edu/) has enabled more accurate estimates of ocean heat content, revealing strong warming of the upper 1500 m in the northern North Atlantic (Ivchenko et al., 2006). Attribution of ongoing warming to anthropogenic influence has been established through analysis of climate model experiments (e.g. Pierce et al., 2006), although the precise mechanisms for regional warming are not yet clear. In the Atlantic sector there is evidence that the meridional overturning circulation (MOC) has slowed in the subtropics since the early 1990s (Bryden et al., 2005). This raises the paradox of warming despite reduced oceanic heat transport and has fuelled an enthusiastic debate (e.g. Hirschi et al., 2006; Latif et al., 2006; Wunsch and Heimbach, 2006). Long-term changes are also compounded by variations associated with other processes, one particular example being the North Atlantic Oscillation (NAO), which has been shown to impact the structure of heat transport (Brauch and Gerdes, 2005).
Please acknowledge this document as: Marsh, R. and Kent, E. (2006). Impacts of Climate Change on Sea Temperature 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
Figures
Figure 1. July 2005 – June 2006 averaged SST anomalies in the North Atlantic/Arctic.
Figure 2. 1970 – 2004 linear trends of observed SST within the UK coastal region.
References
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