Abstract
The cycling of phosphorus in the Mediterranean (CYCLOPS) team investigated phosphate limitation in the Eastern Mediterranean and conducted a phosphate addition experiment in 2002 at the centre of an anticyclonic eddy south of Cyprus. The 2002 and other cruises generated a small database of chlorophyll-a (chl-a) profiles that enabled investigation of the performance of a variety of standard and regional bio-optical algorithms for remote sensing retrievals of chl-a in the region. The standard SeaWiFS OC4V4 and MODIS chlor_a2 algorithms overestimated chl-a as previously reported while a regional algorithm proposed by Bricaud et al. [2002. Algal biomass and sea surface temperature in the Mediterranean basin: intercomparison of data from various satellite sensors, and implications for primary production estimates. Remote Sensing Environment 81, 163-178] and the semi-analytical MODIS chlor_a3 gave improved retrievals. SeaWiFS mean chl-a maps are presented for the Eastern Mediterranean for each month between September 1997 and August 2004 and as multi-annual "climatological" images. The former showed that chl-a in the region decreased over the duration of the time series with reductions in the centre of the eddy, tracked using a quasi-Lagrangian approach, of approximately 33% between 1997 and 1998 and 2002 and 2003. This was not correlated with deep winter mixing represented as heat loss from the sea-surface or dust deposition represented as daily EP-TOMS aerosol index and annual aluminium deposition on the Israeli coast. It is hypothesised that the variations in chl-a are partly a function of the eddy dynamics. Daily SeaWiFS observations show that the 2002 phosphate release was conducted at a period of decreasing chl-a between the winter maximum and summer oligotrophic conditions; however, the rate of seasonal decrease was less than that observed in situ during the week following the phosphate release.
| Original language | English |
|---|---|
| Pages (from-to) | 2990-3010 |
| Number of pages | 21 |
| Journal | Deep-Sea Research Part II: Topical Studies in Oceanography |
| Volume | 52 |
| Issue number | 22-23 |
| DOIs | |
| State | Published - Nov 2005 |
| Externally published | Yes |
Bibliographical note
Funding Information:This work was part funded by the EV Framework 5 CYCLOPS (Cycling of Phosphate in the Eastern Mediterranean Project (EVK3-CT-1999-00037) and by the Natural Environment Research Council core support of Plymouth Marine Laboratory. We would like to acknowledge the masters and crew on the research vessels Aegaeo and Shikmona used to gather in situ data as well as CYCLOPS colleagues who under took cruise organisation and logistics (including Pre Carbo, Leeds University, and Anastasios Tselepides, HCMR Crete) and phosphate release/tracer and buoy operations (Malcolm Liddicoat and Tim Fileman, PML). We would like to thank Ben Wheatley, PML for running the primary production models and Bob Clarke, PML for statistical advice. We also thank staff at the Remote Sensing Data Analysis Service, Plymouth for assistance in satellite data processing and David Blondeau-Patissier for assistance in the MODIS/in situ comparisons. We acknowledge data provided by the NOAA-CIRES Climate Diagnostics Center, Boulder, Colorado, from their Web site at http://www.cdc.noaa.gov/ . Finally, we would like to thank the reviewers Alex Cunningham and Peter Strutton and an anonymous reviewer for comments that improved the paper.
Keywords
- Chlorophyll-a
- Cyprus Eddy
- Ocean colour
- Phosphate addition
- Remote sensing
- SeaWiFS
ASJC Scopus subject areas
- Oceanography