Source water distribution and quantification of North Atlantic Deep Water and Antarctic Bottom Water in the Atlantic Ocean

- ISOW and LSW were the two main source water masses at the southern boundary of NADW.
- WSDW and WSBW contribute up to 15% of deep waters at 45°N.
- Equatorial region and North Western Boundary are important to mixing of deep waters.
- Larger temporal variability was attributed to ISOW and DSOW.

The distribution and quantification of the source waters of the North Atlantic Deep Water (NADW) and the Antarctic Bottom Water (AABW) in the Atlantic Ocean were investigated using 40 years of climatology data (1973-2014) constructed from the dataset available in the 2013 World Ocean Database. The quasi-interdecadal variability of NADW and AABW source waters spanned the late 1980s until early 2010 in the analysis of three World Ocean Circulation Experiment sections (WOCE A05, A10 and A16). The study was performed by applying optimum multiparameter analysis to quantify the mixture of six NADW and AABW source waters (four for NADW and two for AABW). The NADW source waters decrease their contributions from north to south, except for the region between 30°S and 45°S where the Labrador Sea Water (LSW) contribution suggests an upper NADW deepening. In addition, Iceland-Scotland Overflow Water (ISOW) and LSW contribute to the southernmost boundary of NADW in the Southern Ocean. The AABW source waters were observed as far as 45°N with a 15% contribution, with significant recirculation in equatorial regions and higher contributions in Argentine and Brazil basins. The Denmark Strait Overflow Water (DSOW) and ISOW showed the highest temporal variability (±20%) not only near their formation region but also in the South Atlantic. The AABW source waters did not present high temporal variability, although temporal changes were found near their formation region. Based on their spatial distribution, the Argentine and Brazil basins were noted as the main locations to use for investigating this issue. The results provide new insights into the mixing inside the deep Atlantic Ocean and the global circulation cell; the results also specify the source water masses that present higher temporal variability and the suitable locations to observe these changes.

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