Figure 2. Deep ocean circulation patterns in the modern Atlantic and during the LGM. Contours on each plot are of the 13C/12C ratio in dissolved inorganic carbon. For the modern map these data were collected by shipboard bottles that can retrieve samples from any depth in the ocean. For the LGM map the carbonate shells of benthic were analyzed for their carbon isotopic composition. These animals record the isotopic chemistry of the water in which they grew, ~20,000 years ago. For our purposes the most important difference between these two maps is the larger influence of AABW at the latitude of the New England Seamounts during the glacial period.
Image courtesy of Jess Adkins, California Institute of Technology, as modified from Duplessy et al. (1988) Deep water source variations during the last climatic cycle and their impact on the global deep water circulation, Paleoceanography, 3, 343-360.