Mid-Latitude Mesoscale Temperature Variability in Six Multiship XBT Surveys

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Abstract
We discuss the spatial character of mesoscale temperature variability as observed in six midlatitude multiship expendable bathythermograph (XBT) surveys, two from the North Pacific and four from the North Atlantic. These surveys sample mid-ocean regions as well as regions adjacent to the western boundary currents of both subtropical gyres. Mesoscale characteristics exhibit substantial changes between surveys, between ship tracks within each survey and between different portions of individual ship tracks. These results suggest that a single XBT section across a region is unlikely to represent the range of variability within that region satisfactorily. Fluctuations below the mixed layer are strongly vertically correlated, but surface temperatures are not well correlated with those below the mixed layer. We concentrate on the horizontal variability of the temperature at 450 m, and present rms thermal variability values and zonal autocorrelation functions as conventional measures of the variability. ... Abstract We discuss the spatial character of mesoscale temperature variability as observed in six midlatitude multiship expendable bathythermograph (XBT) surveys, two from the North Pacific and four from the North Atlantic. These surveys sample mid-ocean regions as well as regions adjacent to the western boundary currents of both subtropical gyres. Mesoscale characteristics exhibit substantial changes between surveys, between ship tracks within each survey and between different portions of individual ship tracks. These results suggest that a single XBT section across a region is unlikely to represent the range of variability within that region satisfactorily. Fluctuations below the mixed layer are strongly vertically correlated, but surface temperatures are not well correlated with those below the mixed layer. We concentrate on the horizontal variability of the temperature at 450 m, and present rms thermal variability values and zonal autocorrelation functions as conventional measures of the variability. ...

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