Water mass distributions and transports for the 2014 GEOVIDE cruise in the North Atlantic

• Published in: Biogeosciences
• Main Authors: Garcia-ibanez, Maria Isabel, Perez, Fiz F., Lherminier, Pascale, Zunino, Patricia, Mercier, Herle, Treguer, Paul
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Gesellschaft Mbh 2018
• Subjects: Greenland; Irminger Basin; Irminger Sea; East Greenland; Iceland; Labrador Sea; North Atlantic; North East Atlantic
• Online Access: https://archimer.ifremer.fr/doc/00412/52307/53112.pdf; https://archimer.ifremer.fr/doc/00412/52307/53113.pdf; https://archimer.ifremer.fr/doc/00412/52307/56305.pdf; https://archimer.ifremer.fr/doc/00412/52307/56306.pdf; https://doi.org/10.5194/bg-15-2075-2018; https://archimer.ifremer.fr/doc/00412/52307/

We present the distribution of water masses along the GEOTRACES-GA01 section during the GEOVIDE cruise, which crossed the subpolar North Atlantic Ocean and the Labrador Sea in the summer of 2014. The water mass structure resulting from an extended Optimum MultiParameter (eOMP) analysis provides the framework for interpreting the observed distributions of trace elements and their isotopes. Central Waters and Subpolar Mode Waters (SPMW) dominated the upper part of the GEOTRACES-GA01 section in 2014. At intermediate depths, the dominant water mass was Labrador Sea Water, while the deep parts of the section were filled by Iceland–Scotland Overflow Water (ISOW) and North East Atlantic Deep Water. We also evaluate the water mass volume transports across the 2014 OVIDE line (Portugal to Greenland section) by combining the water mass fractions resulting from the eOMP analysis with the absolute geostrophic velocity field estimated through a box inverse model. This allowed us to assess the relative contribution of each water mass to the transport across the section. Finally, we discuss the changes in the distribution and transport of water masses between the 2014 OVIDE line and the 2002–2010 mean state. At the upper and intermediate water levels, colder end-member of the water masses replaced the warmer ones in 2014 with respect to 2002–2010, in agreement with the observed cooling of the surface and intermediate waters. Below 2000 dbar, ISOW increased its contribution in 2014 with respect to 2002–2010, increase related to the observed salinization since 2002. We also observed an increase in SPMW in the East Greenland Irminger Current in 2014 with respect to 2002–2010, which supports the recent deep convection events in the Irminger Sea. The assessment of the relative contribution of each water mass to the Atlantic Meridional Overturning Circulation (AMOC) across the OVIDE line allows identifying the water masses involved in the increase in the AMOC intensity from 2002–2010 to 2014. The increase in the AMOC intensity is related to the increase in the northward transport of the Central Waters in its upper limb, and to the increase in the southward flow of SPMW of the Irminger Basin and ISOW in its lower limb.