Temporal and geospatial characterization of trends in sea surface temperature

This presentation was held at the 24^th International SST Users’ Symposium and GHRSST Science Team Meeting (GHRSST24) held in Ahmedabad, India/Online from 16 – 20 October 2023.

Explore the full program at GHRSST24 on the GHRSST Website here.

Abstract

Sea surface temperature (SST) provides an indicator of the ocean’s physical state. Changes in SST during the past decades are significant, and monitoring its patterns and trends is critical to understanding various oceanographic and climatic processes. We will present SST trends from ESA’s Climate Change Initiative v2.1 data available at https://cds.climate.copernicus.eu. A trend is a time series in the same space as the original parameter after removing seasonalities and noise. We will discuss trends derived employing linear fit and various decomposition methods, including seasonal-trend decomposition using LOESS (STL) and multiple STL (MSTL), and for global oceans, the Bay of Bengal, and the Chesapeake Bay. In addition, implementation challenges will be discussed, i.e., spectral analysis for specifying periodicities and handling an extensive array of data. SST generally shows up-trends with rates in K×decade -1 of 0.07±6% (global), 0.16±8% (Bay of Bengal), and 0.22±50% (Chesapeake Bay). A continuous long-term (1982-2022) analysis helped overcome the shortcomings flagged by the global warming hiatus debate. The geospatial distribution of trend rates is pervasive. Parts of the Southern Ocean, areas around the Peruvian current, the eastern Pacific cold tongue, a North Atlantic patch (due to disruption of the Atlantic Meridional Overturning Circulation), and many smaller coastal segments show negative trends. Conversely, other oceanic parts show an increasing trend at different levels. Some are intense, exceeding 0.4 K×decade -1 , in the North Atlantic (Baffin Bay, Labrador Sea), Arctic (Barents Sea), and other areas. Increasing trends are ubiquitous and, combined with other parameters, can have far-reaching consequences on Earth’s ecosystems.