Abstract's details
SWOT and the drifter’s odyssey in the NW Mediterranean Sea: riding current meanders and escaping eddies
Event: 2025 SWOT Science Team Meeting
Session: Oceanography: Calibration and Validation
Presentation type: Poster
Understanding, monitoring and predicting the sea level changes from regional to local scales are critical issues for coastal populations and ecosystems, and the 30-year record of satellite altimetry observations is an outstanding tool to address them. Yet, interpreting small-scale, rapidly varying nearshore coastal ocean dynamics remains a challenge with the 1-D conventional altimetry measurements. The 2-D SWOT measurements of sea surface heights and derived currents are expected to provide unprecedented insights on small-scale ocean dynamics. They will also enable us to revisit our understanding of the 1-D altimetry physical content and how it captures such processes, finally leading to the improvement of long altimetry time series for regional and coastal studies. This presupposes a clear understanding of the signals captured by SWOT, using the observations and models available.
Here, we explore SWOT L3 sea surface height and current measurements in the Northwestern Mediterranean Sea, at regional and local scales. We take advantage of the wealth of multiplatform data available in the region, such as in situ observations, model simulations, nadir altimetry, and other remote sensing observations (Sea Surface Temperature, Ocean Color, SAR images…) to analyze specific events.
Starting from the one-year odyssey of a drifter throughout the Northwestern Mediterranean Sea basin, carried by current meanders, eddies and fronts, we explore the coherency of its velocity and trajectory with the geostrophic currents derived from SWOT observations, and also compare with the currents obtained from a Symphonie numerical simulation in the area. This 15m-drogued drifting buoy was launched in May 2023 under the SWOT Phase Sampling Phase track 3 within the frame of the SWOT Calval campaigns, and ended its journey in June 2024 in the Tyrrhenian Sea. It thus offers the opportunity to explore different aspects of SWOT sampling, with 1-day and 21-day repeat periods. In addition, the Rossby radius of deformation is about 10 km in the region, which is close to the intrinsic spatial resolution of SWOT measurements, meaning that SWOT geostrophic currents are estimated at the limit of the geostrophy approximation frame. The numerical simulation provides useful insights on geostrophy and ageostrophy contributions in the region to better understand the content of SWOT current estimates at the scale of the basin.
One of the most striking ocean dynamics features encountered by the drifter during its journey is an anticyclonic eddy located around the Capraia Island in the Corsica Channel, where it remains stuck for more than a month. This eddy, with a diameter of about 50 km, including the small Capraia Island at its center, is known to have seasonal characteristics, appearing during Summer and lasting until Fall. It has been sampled by SWOT at the beginning of the Science Phase, which provides an opportunity to investigate the quality of SWOT SSH and current estimates in a more coastal and local domain. Two tracks of the historic Topex-Jason nadir altimetry suite also pass over the Capraia Island, which provides a long time series of coastal altimetry observations in the region. This configuration is thus a very nice opportunity to revisit nadir altimetry at the light of SWOT and analyze how the various instruments (including SWOT nadir altimeter) capture the Capraia Island eddy.
Back to the list of abstractHere, we explore SWOT L3 sea surface height and current measurements in the Northwestern Mediterranean Sea, at regional and local scales. We take advantage of the wealth of multiplatform data available in the region, such as in situ observations, model simulations, nadir altimetry, and other remote sensing observations (Sea Surface Temperature, Ocean Color, SAR images…) to analyze specific events.
Starting from the one-year odyssey of a drifter throughout the Northwestern Mediterranean Sea basin, carried by current meanders, eddies and fronts, we explore the coherency of its velocity and trajectory with the geostrophic currents derived from SWOT observations, and also compare with the currents obtained from a Symphonie numerical simulation in the area. This 15m-drogued drifting buoy was launched in May 2023 under the SWOT Phase Sampling Phase track 3 within the frame of the SWOT Calval campaigns, and ended its journey in June 2024 in the Tyrrhenian Sea. It thus offers the opportunity to explore different aspects of SWOT sampling, with 1-day and 21-day repeat periods. In addition, the Rossby radius of deformation is about 10 km in the region, which is close to the intrinsic spatial resolution of SWOT measurements, meaning that SWOT geostrophic currents are estimated at the limit of the geostrophy approximation frame. The numerical simulation provides useful insights on geostrophy and ageostrophy contributions in the region to better understand the content of SWOT current estimates at the scale of the basin.
One of the most striking ocean dynamics features encountered by the drifter during its journey is an anticyclonic eddy located around the Capraia Island in the Corsica Channel, where it remains stuck for more than a month. This eddy, with a diameter of about 50 km, including the small Capraia Island at its center, is known to have seasonal characteristics, appearing during Summer and lasting until Fall. It has been sampled by SWOT at the beginning of the Science Phase, which provides an opportunity to investigate the quality of SWOT SSH and current estimates in a more coastal and local domain. Two tracks of the historic Topex-Jason nadir altimetry suite also pass over the Capraia Island, which provides a long time series of coastal altimetry observations in the region. This configuration is thus a very nice opportunity to revisit nadir altimetry at the light of SWOT and analyze how the various instruments (including SWOT nadir altimeter) capture the Capraia Island eddy.