Physical Changes in the Patagonian Shelf

MOREIRA, DIEGO; MARTIN, JACOBO; TONINI, MARIANO H.; SARACENO, MARTIN; PISONI, JUAN P.

Global Change in Atlantic Coastal Patagonian Ecosystems : A Journey Through Time

Springer Nature

Lugar: Cham; Año: 2021; p. 43 - 71

The Patagonian Shelf is one of the most productive and dynamic continental shelves of the world. It is a critical habitat for a large number of marine organisms. These organisms are strongly affected by physical conditions, including winds, waves, rivers, as well as the topography of the seafloor and the shape of the coastline. Changes in these environmental conditions can affect productivity, species population sizes, and community structure within the coastal ocean ecosystem. In this chapter, the baseline knowledge of the physical processes as well as the observed and expected changes that affect the Patagonian Shelf and in particular the coastal area, are reviewed. We also computed trends of satellite sea surface temperature (SST) and chlorophyll-a (chl-a) concentration for years 2002-2020, and of sea surface height (SSH) for years 1993-2020. A significant positive trend (up to 0.04 °C per year) is observed north of ~50 °S and negative trend values (up to -0.02 °C per year) are observed south of 50 °S in SST data. The negative SST trend observed in the southern portion of the region is associated with the positive trend observed in the dominant westerly winds within those latitudes. Chl-a shows a linear trend during spring as large as 2 mg m-3 over a 10-yr period in the outer portion of the continental shelf, between 50 and 40 °S. The linear trend in SSH ranges between 2 and 5 mm yr-1 (95% confidence level) in good agreement with previous results. In the northern region, the positive linear trends are associated with local changes in the density field caused by advective effects in response to a southward displacement of the South Atlantic High. Recent studies show that the Southern Annular Mode (SAM) is one of the main drivers that might explain a portion of the interannual variability observed in the Patagonian Shelf. Findings reported here are in agreement with the main results and predictions reported in the Intergovernmental Panel On Climate Change (IPCC) report for the Southwestern Atlantic (IPCC 2014).