GOES-16 ABI True Color RGB

Upwelling in the Gulf of Tehuantepec

1 December 2020 00:00 UTC-3 December 16:24 UTC

GOES-16 ABI True Color RGB
GOES-16 ABI True Color RGB

Regional topography and winds drive a strong upwelling of cold ocean waters and an increase in phytoplankton growth in the Gulf of Tehuantepec.

Last Updated

21 December 2020

Published on

16 December 2020

By Hayley Evers-King and Jochen Karl Kerkmann (EUMETSAT), Ivan Smiljanic (CGI) and Ben Loveday (Innoflair)

Tehuantepecer, or Tehuano wind, occurs between October and March, e.g. in winter, related to large-scale cold air outbreaks from the north.

A strong wind episode in the Chivela Pass (between Mexican and Guatemalan mountains) was dynamically forced by the plunging of cold air behind an intense and very elongated cold front. This front stretched from the south-western area of the Gulf of Mexico to the north-eastern coast of America (Figure 1), bringing the cold air from the far continental north all the way down to south of the Mexican coast.

Image comparison

GOES-16 ABI Airmass RGB image, overlaid with 850 hPa level wind barbs compare1
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Figure 1: GOES-16 ABI Airmass RGB image, overlaid temperature advection field from ECMWF model output (left) and 850 hPa level wind barbs  (right), 1 December 2020, 00:00 UTC. Credit: ePort, EUMeTrain.

Clouds streets are very prominent features of strong cold advection — clearly seen behind the frontal line in the quasi-linear cumulus cloud formations (Figure 2).

GOES-16 ABI True Color RGB
Figure 2: GOES-16 ABI True Color RGB image, 1 December, 18:00 UTC, showing cold front and accompanied cloud streets over the ocean.

Advection of cold air, more than -18 °C further south was channeled through Chivela Pass, with accelerated flow (Figure 3).

GOES-16 ABI Airmass RGB image, overlaid with 850 hPa level temperature advection field
Figure 3: GOES-16 ABI Airmass RGB image, overlaid with 850 hPa level temperature advection field (more than 18°C drop) from ECMWF model output, 1 December 00:00 UTC. Credit: ePort, EUMeTrain.

A consequence of this strong wind circulation, was upwelling in the ocean waters in the Gulf of Tehuantepec. The winds drove an offshore movement of surface waters, which were then replaced by water which upwelled from the depths. This water was both colder and more nutrient rich than the surface water it replaced.

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Figure 4: Coincident high resolution Sea Surface Temperature, 1 km (left) and chlorophyll-a concentrations 300 m (right ), 3 December, derived from Sentinel-3A SLSTR and OLCI instruments respectively. Level 1 data from OLCI is also used to provide a true colour, Digital Elevation Model (DEM) elevated image of the topography that affects wind travelling from the north across the Isthmus and into the Gulf of Tehuantepec. Higher levels of chlorophyll-a (yellow) are associated to parts of the upwelling plume seen in the cold SST (blue).

The signature of this phenomena can be clearly seen in satellite-derived sea surface temperature (SST) and in chlorophyll-a concentrations derived from satellite ocean colour measurements (Figure 4), as measured by the SLSTR and OLCI sensors aboard the Sentinel-3A satellite on 3 December 2020.

A longer term perspective on this event can be gained from looking at a multi-sensor merged record of sea surface temperature. Figure 5 shows the SST in the region from November to December 2020. The enhancement of the cold upwelling feature grows clearly over the month. The upwelling in this region, as a result of the wind circulation, is observed on an annual basis, with variability in its strength influenced by the El Nino Southern Oscillation (ENSO). Ultimately upwelling dynamics play an important role in nutrient cycling and primary production in the oceans, with the potential to affect higher tropic levels, such as fish and mammal populations, on which many economic activities depend.

Figure 5: A level-4 SST product from the Copernicus Marine Service shows the development of the cold upwelling circulation from 4 November-4 December 2020. The product is the OSTIA diurnal skin Sea Surface Temperature product which uses in-situ and satellite data from a range of infra-red radiometers.

The phenomenon can also be seen on the GOES-16 Natural Color RGB with ASCAT winds overlaid (Figure 6).

GOES-16 Natural Color RGB
Figure 6: GOES-16 Natural Colour RGB overlaid with Metop-B ASCAT wind barbs, 1 December 18:00 UTC.