Global patterns of change and variation in sea surface temperature and chlorophyll a

TLDR

Decadal changes in oceanic environments pose challenges for resource management and utilization. The study investigates global temporal variation in sea surface temperature and chlorophyll‑a and their co‑variation over a 14‑year period. Statistical methods partition variation into inter‑annual and annual components while accounting for daily autocorrelation. SST variability increases with latitude, chlorophyll‑a variability peaks in mid‑latitudes, and their covariation reveals small‑scale mechanisms, regional warming and contrasting Chl‑a trends, and spatially heterogeneous decadal patterns that require regionally tailored monitoring.

Abstract

Changes over the scale of decades in oceanic environments present a range of challenges for management and utilisation of ocean resources. Here we investigate sources of global temporal variation in Sea Surface Temperature (SST) and Ocean Colour (Chl-a) and their co-variation, over a 14 year period using statistical methodologies that partition sources of variation into inter-annual and annual components and explicitly account for daily auto-correlation. The variation in SST shows bands of increasing variability with increasing latitude, while the analysis of annual variability in Chl-a shows mostly mid-latitude high variability bands. Covariation patterns of SST and Chl-a suggests several different mechanisms impacting Chl-a change and variance. Our high spatial resolution analysis indicates these are likely to be operating at relatively small spatial scales. There are large regions showing warming and rising of Chl-a, contrasting with regions that show warming and decreasing Chl-a. The covariation pattern in annual variation in SST and Chl-a reveals broad latitudinal bands. On smaller scales there are significant regional anomalies where upwellings are known to occur. Over decadal time scales both trend and variation in SST, Chl-a and their covariance is highly spatially heterogeneous, indicating that monitoring and resource management must be regionally appropriate.