Five Year Mean Sea-surface Salinity in the Northern Gulf of Mexico for 2005 through 2009

These images were created by combining the mean sea-surface salinity values to produce seasonal representations for winter, spring, summer and fall. Winter includes the months of January, February and March; spring includes the months of April, May and June; summer includes the months of July, August and September; fall includes the months of October, November and December. Sea-surface salinity values were originally obtained from the Naval Research Laboratory at the Stennis Space Center (NRL/SSC). NRL/SSC processed MODIS-Aqua satellite imagery covering the Gulf of Mexico, for a 5-year time period from January 2005 through December 2009. The Gulf of Mexico was divided into three regions, western, central and eastern. For purposes of this image, the three regions were joined in ArcMAP 10. Sea-surface salinity was estimated from the ocean color imagery, based on an empirical relationship between colored dissolved organic matter (CDOM) absorption and salinity. Researchers at NRL have exploited this relationship to empirically estimate salinity from ocean color satellite imagery, since the absorption slope difference between 412 nm and 443 nm can be used as a proxy to estimate the CDOM absorption coefficient: Salinity = 36.208 - 46.488x + 27.683x2 - 8.338x3 + 0.965x4 In the above equation, x = difference between the absorption coefficients at 412 and 443 nm (a412-a443). The algorithm was developed using in situ data from a wide variety of locations and has been validated with independent ship and mooring data (Ladner et al. 2006; 2008). Currently the algorithm has an accuracy of about 1 PSU and is valid in coastal waters where salinity is strongly impacted by freshwater discharge (out to approximately mid-shelf). The algorithm is based on the difference in total absorption at 412 and 443 nm. NRL produced salinity images from the MODIS satellite ocean color data at both 250 m and 1 km spatial resolution in the Gulf of Mexico using this relationship. The salinity product derived from the ocean color imagery is still experimental and requires further validation. It is expected that different mixing regimes will affect the conservative nature of the CDOM/salinity proxy relationship, resulting in deviations from the above empirical relationship. These values were then reclassified into salinity ranges in accordance with the Coastal and Marine Ecological Classification Standard (CMECS). There are five CMECS categories presented: oligohaline (0 - < 5, shown in red), mesohaline (5 - < 18, shown in green), lower polyhaline (18 - < 25, shown in purple), upper polyhaline (25 - < 30, shown in yellow), and euhaline (> 30, shown in blue).

This project was undertaken to assess the utility of satellite-derived products and modeled data for resource managers to characterize pelagic habitats in the absence of dense, time series in situ data. There were several steps involved in this process, including: identifying the most useful physicochemical parameters for characterizing the water column; assessing the fit of satellite-derived and modeled data as a proxy for in situ data; evaluating alternative, automated classification methodologies; querying resource managers for product improvement opportunities; and developing a practical example of a management application. Sea-surface salinity was one of the satellite-derived products assessed as a proxy for in situ data.

10897

The NOAA Office for Coastal Management - Gulf Region received this data from another federal agency. Questions regarding the original data collection and/or processing should be directed to that agency (see lineage source citation).

Any conclusions drawn from the analysis of this information are not the responsibility of the NOAA Office for Coastal Management or its partners.NOAA makes no warranty regarding these data, expressed or implied, nor does the fact of distribution constitute such a warranty. NOAA, NESDIS, NODC and NCDDC cannot assume liability for any damages caused by any errors or omissions in these data, nor as a result of the failure of these data to function on a particular system.

None

None

Unique values were generated for each image in ArcMAP 10. The unique values were then manually reclassified into appropriate Coastal and Marine Ecological Classification Standard categories.

Values were assigned to categories in accordance with the Coastal and Marine Ecological Classification Standard.

not applicable