Variability of particulate organic carbon concentration in the north polar Atlantic based on ocean color observations with Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS)

Abstract

We use satellite data from Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS) to investigate distributions of particulate organic carbon (POC) concentration in surface waters of the north polar Atlantic Ocean during the spring–summer season (April through August) over a 6‐year period from 1998 through 2003. By use of field data collected at sea, we developed regional relationships for the purpose of estimating POC from remote‐sensing observations of ocean color. Analysis of several approaches used in the POC algorithm development and match‐up analysis of coincident in situ–derived and satellite‐derived estimates of POC resulted in selection of an algorithm that is based on the blue‐to‐green ratio of remote‐sensing reflectance Rrs (or normalized water‐leaving radiance Lwn). The application of the selected algorithm to a 6‐year record of SeaWiFS monthly composite data of Lwn revealed patterns of seasonal and interannual variability of POC in the study region. For example, the results show a clear increase of POC throughout the season. The lowest values, generally less than 200 mg m−3, and at some locations often less than 50 mg m−3, were observed in April. In May and June, POC can exceed 300 or even 400 mg m−3 in some parts of the study region. Patterns of interannual variability are intricate, as they depend on the geographic location within the study region and particular time of year (month) considered. By comparing the results averaged over the entire study region and the entire season (April through August) for each year separately, we found that the lowest POC occurred in 2001 and the highest POC occurred in 2002 and 1999.