The objective of this project is to characterize the thermal variability of the upper few hundred meters of the North Atlantic.
The ocean serves as a thermal capacitor, storing and redistributing heat. Consequently, the upper ocean plays a fundamental role in determining patterns of climatic change on time scales ranging from seasons through decades. By understanding the ocean's thermal variability, we hope to improve our ability to forecast climatic changes.
Our approach is to partition the North Atlantic into regions and to examine the spatial and temporal variability of temperature observations within each region. Monthly and seasonal means, standard deviations, quartiles and medians for each region are compared to corresponding statistics for the same calendar month or season for the entire record in order to determine unusually warm or cold periods. This information is used to explore whether thermal anomalies exhibit coherent spatio-temporal patterns.
We have used the COADS (Comprehensive Ocean-Atmosphere Data Set) summaries of North Atlantic sea-surface temperatures to determine the extent to which seasonal averages of observations from 1950 through 1992 within 2-degree longitude by 2-degree latitude cells have correlated temporal behavior. While correlation coefficients for seasonal anomalies of adjacent cells can be can be as high as 0.9, they can also be less than 0.5, the least correlated behavior being in the northwestern Atlantic in the vicinity of the Gulf Stream. Observations have also been partitioned into 6-degree longitude by 4-degree latitude cells to study the seasonal variability on larger spatial scales. Cluster analysis has been used to merge the 6x4 cells into larger regions on the basis of similar thermal behavior. SST-anomaly correlation coefficients for pairs of 6x4 cells within common regions have essentially the same distribution as correlation coefficients for pairs of 2x2 cells within common 6x4 cells. (See Thacker and Lewandowicz, 1995.)
Thacker, W. C., and R. Lewandowicz, 1997: Partitioning the North Atlantic into regions of similar seasonal sea-surface temperature anomalies. International Journal of Climatology, 17, 3-23.
Thacker, W. C. and R. Lewandowicz, 1997: A comparison of low-dimensional representation of sea-surface temperature anomalies in the North Atlantic, International Journal of Climatology, 17, 953 - 967.