Cara Wilson and Victoria J. Coles
Journal of Geophysical Research, 110, C10001, doi:10.1029/2004JC002724, 2005
We evaluate the relationships of monthly climatological satellite measurements of sea-surface height, temperature and chlorophyll to climatological subsurface parameters (mixed layer depth, thermocline depth and nutricline depth) on a global scale to determine the spatial variability and mechanisms underlying their relationships. There are well-defined physical regimes in the tropics (20°S-20°N); where surface and subsurface physical parameters are predominantly positively correlated, due to the dominance of baroclinic processes, and the extratropics (20°-60° latitude); where they are negatively correlated, and barotropic processes dominate. The biological regimes differ; correlations between surface chlorophyll and subsurface parameters are variable in the tropics, positive at mid-latitudes (20°-40° latitude), and negative at high latitudes. We interpret these changing relationships in the context of differing underlying biophysical processes: dynamic uplift causing nutrient entrainment into the euphotic zone in parts of the tropics, seasonal entrainment of nutrients into the euphotic zone at mid-latitudes and seasonal controls on light supply at high latitudes. Together with the physical regimes, these biophysical conceptual models explain the relatively complex, broad-scale relationships between global satellite derived sea surface height, temperature, and chlorophyll-a on a climatological seasonal basis. This study of the background seasonal state will aid future interpretation of higher and lower frequency variability in satellite measurements.
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