Detection and Probability of Ocean Fronts in AMSR-E Satellite Data

Kelsey M. Obenour¹, Peter C. Cornillon², Christian E. Buckingham^2
1REU participant at Graduate School of Oceanography/University of Rhode Island, Narragansett, RI
²Graduate School of Oceanography/University of Rhode Island, Narragansett, RI

Abstract: Many oceanographic characteristics are affected by the dynamics of ocean fronts – regions of large horizontal gradients in ocean properties. As a result numerous studies have been undertaken to characterize ocean fronts, especially at the ocean surface. The studies have been conducted on sea surface temperature (SST) fields obtained from satellite-borne infrared instruments, primarily the Advanced Very High Resolution Radiometer. However, a significant problem with SST fields obtained from infrared instruments is their inability to ‘see’ through clouds. By contrast the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) aboard the AQUA spacecraft measures SST with a passive microwave instrument, making observations regardless of cloud presence possible. To our knowledge, a systematic study of global ocean fronts has not been conducted on SST fields obtained with AMSR-E data. The University of Rhode Island single image edge detection algorithm has been applied to seven years of AMSR-E data. The resulting data sets consists of  two, nearly complete, global maps of the location of SST fronts per day from which we determined frontal probability as a function of space and time on a global scale. A remarkable characteristic of the global monthly fields of frontal probability is the suggestion of zonal bands at mid-latitudes in all major ocean basins separated by a dominant meridional length scale of order 300 to 450 km. This scale shows very little seasonal variation and is virtually identical in the northern and southern hemispheres. This suggests that it does not depend on seasonal forcing nor on the shape and size of the basin; i.e., that it is a fundamental characteristic of mid-latitude oceans. These zonal bands are reminiscent of the banding seen by Maximenko and co-authors in sea surface height fields obtained with altimeter data and with float data. The dynamical processes resulting in this banding are unknown at this time.