Chlorophyll

These data are part of a ocean observation study by Stabeno, Napp, and Whitledge sponsored, in part, by the North Pacific Research Board (Project 517; http://doc.nprb.org). The grant was titled "Sentinels for Bering Sea ecosystem change." Moorings have been maintained on the southeastern Bering Sea shelf at four sites: M2 (56.9B0N, 164.1B0W) since 1995, M4 (57.9B0N, 168.9B0W) since 1996; M5 (59.9B0N, 171.7B0W) and; M8 (62.2B0N 174.7B0W) since 2004. Shipboard measurements of temperature, salinity, nutrients, chlorophyll, fluorescence and zooplankton were collected around the moorings and along the 70-m isobath on 3 cruises (3MF05, 16 April b?? 7 May; 3TT05, May 12 - 28; 8MF05, 21 September b?? 4 October) to groundtruth the in situ sensors on the moorings. This long-term monitoring supports major findings: (1) Over the southeastern shelf, the timing of the spring phytoplankton bloom is determined by the presence of ice, with an early bloom occurring if ice is present after mid-March and a later bloom if there is no sea-ice after mid-March; (2) during 2001-2005, the southeastern Bering Sea shelf underwent a marked warming (~3B0C) that was closely associated with a decrease of sea ice; with shifts in the atmospheric forcing, colder conditions returned to the Bering Sea shelf in the winter 2006 and continued into winter/spring 2007; (3) nutrients supply and summer salinity over the shelf has not significantly changed during the last three decades; (4) in association with the warming there is an indication that the abundance of cold-water zooplankton species (e.g. Calanus marshallae ) has been reduced; (5) from hydrography collected in May and September 2005 along the 70 m isobath starting at M2 in the south and ending at M8 in the north, it is evident that the structure of southern shelf is dominated by temperature, while the northern shelf is dominated by salinity. In addition, the location of the boundary between the southern shelf and northern shelf appears to vary from one year to the next and is mainly, but not completely dependent upon maximum ice extent during the spring.