A water mass is defined primarily by its salinity, temperature, and chemical properties. North Atlantic Deep water (NADW) is a water mass that is derived from the warm salty waters of the Gulf Stream.  As this water travels north it cools and becomes denser.  At high northern latitudes, it becomes dense enough to sink, entraining ambient waters on its descent to fill most of the Atlantic Ocean between depths from 2000-4000 meters. The formation of NADW is important for the transport of heat to the higher latitudes.  In the modern ocean, fresher water masses from the southern ocean, Antarctic Bottom Water (AABW) and Antarctic Intermediate Water (AAIW) lie below and above NADW, respectively.  These different water masses can also be recognized by their carbon isotope signatures (See figure on left).

Reconstructions using carbon isotopes measured on benthic foraminifera suggest that during the peak of the last ice age, or the “last glacial maximum” (21,000-18,000 years ago), NADW did not sink as deeply as it does today. This less deep counter part to NADW is called Glacial North Atlantic Intermediate Water (GNAIW).  Given the reduced contribution by North Atlantic water, most of the western Atlantic below 2,000 m was filled with AABW.  How far north AAIW penetrated is unknown, because there are no sediment cores available between ~ 27S and 24N at appropriate depths to identify the water masses. 

The goal of this cruise is to recover cores along a depth transect between from 400 and 4000m to collect cores that sample modern AAIW, NADW, and AABW, as well as their glacial counterparts. 

See this article published in Oceanus for further explanation.

Curry and Oppo, 2005