Observations: oceanic climate and sea level

• Main Authors: Bindoff, N., Willebrand, J., Artale, V., Cazenave, A., Gregory, J., Gulev, S., Hanawa, K., Le Quéré, C., Levitus, S., Nojiri, Y., Shum, C.K., Talley, L., Unnikrishnan, A.
• Other Authors: Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Centre National de la Recherche Scientifique (CNRS)
• Format: Book Part
• Language: English
• Published: HAL CCSD 2007
• Subjects: [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Indian; Pacific; Southern Ocean; North Atlantic
• Online Access: https://hal.science/hal-00287145; https://hal.science/hal-00287145/document; https://hal.science/hal-00287145/file/Bindoff2007.pdf

Contribution of Working Group I to the Fourth Assessment report of the Intergouvernmental Panel on Climate Change The oceans are warming. Over the period 1961 to 2003, global ocean temperature has risen by 0.10°C from the surface to a depth of 700 m. Consistent with the Third Assessment Report (TAR), global ocean heat content (0–3,000 m) has increased during the same period, equivalent to absorbing energy at a rate of 0.21 ± 0.04 W m–2 globally averaged over the Earth’s surface. Two-thirds of this energy is absorbed between the surface and a depth of 700 m. Global ocean heat content observations show considerable interannual and inter-decadal variability superimposed on the longer-term trend. Relative to 1961 to 2003, the period 1993 to 2003 has high rates of warming but since 2003 there has been some cooling. Large-scale, coherent trends of salinity are observed for 1955 to 1998, and are characterised by a global freshening in subpolar latitudes and a salinification of shallower parts of the tropical and subtropical oceans. Freshening is pronounced in the Pacific while increasing salinities prevail over most of Atlantic and Indian Oceans. These trends are consistent with changes in precipitation and inferred larger water transport in the atmosphere from low latitudes to high latitudes and from the Atlantic to the Pacific. Observations do not allow for a reliable estimate of the global average change in salinity in the oceans. Key oceanic water masses are changing; however, there is no clear evidence for ocean circulation changes. Southern Ocean mode waters and Upper Circumpolar Deep Waters have warmed from the 1960s to about 2000. A similar but weaker pattern of warming in the Gulf Stream and Kuroshio mode waters in the North Atlantic and North Pacific has been observed. Long-term cooling is observed in the North Atlantic subpolar gyre and in the central North Pacific. Since 1995, the upper North Atlantic subpolar gyre has been warming and becoming more saline. It is very likely that up to the end of the 20th ...