Making use of the fine resolution of satellite SAR imagery, we observe small eddies during the spring and summer months in several locations in Lake Superior. During these months there is a thermal gradient between warmer nearshore waters and colder offshore waters which enhances cyclonic coastal currents. Using spaceborne SAR imagery from the European Space Agency's ERS-1 and ERS-2 missions from 1992 to 1998, we observe small eddies, identifying and mapping basic eddy characteristics including diameter, location, and rotational sense. In total, 45 eddies were located, of which 41 were cyclonic and 4 anticyclonic. Average diameter was 9.8. km and average distance to shore was 8.1. km. Based on sea surface temperature data from AVHRR, the eddies are located within the region of sharp thermal gradients of order 3-5 °C per 3. km. Spatial and temporal coverage was uneven, however, more eddies were seen in SAR images taken in late summer along the southern and eastern shores as well as areas where the boundary current interacts with topographic features including islands and promontories.
Bibliographical noteFunding Information:
Support for this research was provided by student fellowships of the UM Department of Earth Sciences to PM and by NSF grant OCE-0825576 and McKnight Land Grant Professorship awarded to KM. BH was supported by the National Aeronautics and Space Administration through a contract with the Jet Propulsion Laboratory, California Institute of Technology. All SAR images were provided by the European Space Agency through an approved Envisat principal investigator study (BH).
- Great Lakes
- Lake Superior
- Remote sensing