Water mass census in the Nordic seas using climatological and observational data sets

• Main Authors: Piacsek, S., Allard, R., McClean, J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Societa italiana di fisica 2008
• Subjects: 551.46 Idrosfera; Geologia sottomarina e Oceanografia (Classificare qui le acque marine; l'Idrografia; l'Oceanografia fisica; le opere interdisciplinari sulla Scienza del mare; sugli oceani e i mari); Arctic; Greenland; Norwegian Sea; Greenland Sea; Iceland; Nordic Seas
• Online Access: http://eprints.bice.rm.cnr.it/16354/; http://eprints.bice.rm.cnr.it/16354/1/ncc9277.pdf; https://www.sif.it/riviste/sif/ncc/econtents/2008/031/02/article/1

We have compared and evaluated the water mass census in the Greenlend-Iceland-Norwegian (GIN) Sea area from climatologies, observational data sets and model output. The four climatologies evaluated were: the 1998 and 2001 versions of theWorld Ocean Atlas (WOA98, WOA01), and the United States Navy’s GDEM90 (Generalized Digital Environmental Model) and MODAS01 (Modular Ocean Data Assimilation System) climatologies. Three observational data sets were examined: the multidecadal (1965-1995) set contained on the National Oceanographic Data Center’s (NODC) WOD98 (World Ocean Data) CD-ROM, and two seasonal data sets extracted from observations taken on six cruises by the SACLANT Research Center (SACLANTCEN) of NATO/Italy between 1986-1989. The model data is extracted from a global model run at 1/3 degree resolution for the years 1983-1997, using the POP (Parallel Ocean Program) model of the Los Alamos National Laboratory. The census computations focused on the Norwegian Sea, in the southern part of the GIN Sea, between 10◦W-10◦E and 60◦N-70◦N, especially for comparisons with the hydrocasts and the model. Cases of such evaluation computations included: a) “short term” comparisons with quasi-synoptic CTD surveys carried out over a 4-year period in the southeastern GIN Sea; b) “climatological” comparisons utilizing all available casts from the WOD98 CD-ROM, with four climatologies; and c) a comparison between the WOA01 climatology and the POP model output ending in 1997. In this region in the spring, the fraction of ocean water that has salinity above 34.85 is ∼ 94%, and that has temperatures above 0◦C is ∼ 33%. Three principal water masses dominated the census: the Atlantic water AW, the deep water DW and an intermediate water mass defined as Lower Arctic Intermediate Water (LAIW). Besides these classes, both the climatologies and the observations exhibited the significant presence of deep water masses with T-S characteristics that do not fall into the “named” varieties, e.g., Norwegian Sea or Greenland Sea deep water (NSDW, GSDW). The seasonal volumetric changes for the Atlantic (AW), intermediate (LAIW) and deep waters (DW) in the GIN Sea are in reasonably good agreement between the climatologies, and with the results of hydrographic census surveys. Typical seasonal changes (spring-summer) involve about 30 × 103 km3 of AW increase and 33 × 103 km3 of LAIW decrease, and a decrease of about 32 × 103 km3 of DW between spring and autumn.