Revisiting the Meteor 1925–1927 hydrographic dataset reveals centennial full-depth changes in the Atlantic Ocean

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Abstract

[1] The hydrographic data set of the German Atlantic Expedition (GAE) 1925–1927 is compared with the contemporary profiling float and ship-based hydrography to reveal full-depth changes in the Atlantic Ocean between 19°N and 64°S. The volume-mean warming over the last 80 years amounts to 0.119 ± 0.067 °C, accompanied by an increase in salinity of 0.014 ± 0.010. A clear vertical structure of these changes is observed: on average, the ocean has warmed by 0.272 ± 0.093 °C and became saltier by 0.030 ± 0.014 down to about 2000 m, but cooled and freshened slightly in the deeper layers. These changes can be traced throughout the whole hydrographic survey, indicating the basin-wide character of the observed changes on a centennial timescale. The observed warming is consistent with climate model simulations over the 20th century, suggesting an attribution to anthropogenic forcing. Comparison with the pre-GAE cruises reveals no discernible warming between the 1870s and 1906/1911.

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