Dr. Mati Kahru

Scripps Institution of Oceanography

University of California San Diego

Email: mkahru@ucsd.edu

Research Interests:

Satellite detection of ocean fronts and the use of frontal statistics in ocean ecology

Abstract

Fronts are known as important factors that affect many physical, chemical and biological processes in the ocean. For example, fronts in the California Current System affect the uptake of nutrients by phytoplankton and the sinking flux of carbon. The export of carbon from the surface layer is important in mitigating the effect of anthropogenic carbon emissions to the atmosphere and its quantitative estimates are needed. On the other hand, frontal frequencies are affected by long-term processes such as ENSO and trends related to climate change. For example, the North-East Pacific warm anomalies of 2014-2016 coincided with minima in frontal frequencies of both chlorophyll and temperature and with the historically unprecedented high SST and low chlorophyll concentration. The export flux of carbon was certainly reduced but its accurate quantification is difficult. Fronts are present in many scales and the detection of fronts and their statistics is dependent on the resolution, signal to noise ratio, temporal and spatial merging and on other characteristics of the satellite imagery. We have been using the well-known histogram-based Cayula and Cornillon (1992) edge detection (Single Image Edge Detection) but are now testing the Holistically-Nested Edge Detection (HED method). A comparison of the two methods and the advantages of HED will be presented