Adopting a Swot crossover for biophysical studies

Image of the Month - July 2018

Oceanic fronts derived from altimetry with the finite-size Lyapunov exponent technique (FSLEs, in grey) on May 9, 2018, overlaid on sampling stations (red crosses) along the Beautemps-Beaupré trajectory during the PROTEVS-BioSwot campaign, and on micro-organisms density (color scale) computed from in situ instrument samplings. The FSLE filaments seem to constitute barriers to the dispersion of the micro-organisms (Credits MIO/LOcean)


Swot tracks during the calval Fast-sampling orbit phase. The green and red dots are adopted crossovers.

Swot is an incoming Nasa, Cnes, CSA, and UKSA satellite mission which will provide observations of water elevation over the ocean and on inland waters at unprecedented high resolution. For the ocean, Swot observations will provide a major advancement in our capacity to study the so-called ocean fine scales, a highly energetic ocean regime with spatial scales of the the order of 10-100 km and temporal scales of the order of days to weeks. Besides their important role for physical processes, the fine scales are especially relevant for marine biology. The submesoscale features temporal scales of days to weeks are the same than key ecological processes like plankton division times and bloom durations.

The nominal orbit of Swot will cover almost the global ocean (up to 77.6 latitudes), but its repetitivity will be of 21 days. However, for the first six months after its launch in 2021, Swot will be in a temporary fast-sampling phase, which will allow to observe only a much reduced portion of the ocean, but with a one-day repeat cycle, and high resolution on the swath. This will be an unprecedented opportunity to observe the ocean upper dynamics with high resolution in both space and in time, ideal for biophysical studies. The fast sampling phase is characterized by “crossover diamonds”, i.e. areas of about 150x150 km where two Swot tracks are crossing each other. In preparation to the Swot launch, a consortium of three scientific programs (BioSwot, PRE-Swot, and PROTEVS-Swot) “adopted” the crossover south of the Balearic Islands and performed in 2018 a first pre-launch survey. The Swot science team is encouraging teams to adopt other crossovers (see Swot orbit page for more information on their location).

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  • The BioSWOT project from CNES develops a collaboration between the MIO (Mediterranean Institute of Oceanography), the SHOM (Service Hydrographique et Océanographique de la Marine) and the IMEDEA and SOCIB. A.Doglioli et G.Grégori have been onboard the BHO Beautemps Beaupré for the PROTEVS*-SWOT** cruise (PI F.Dumas) in the Occidental Mediterranean Sea, South of the Baleares Islands from April 28th to May 16th.