Séminaire
I will discuss two new pieces of work and then try to bring them together with an analysis of existing records of benthic foram d18O across the last glacial cycle. First, I will explain how we have used depth profiles of d18O in the Atlantic at the Last Glacial Maximum to measure the ratio of Southern Source water transport to vertical diffusion (psi/kappa in the notation of Physical Oceanography). This value is eight times larger at the LGM than it is in the modern ocean. We believe that this dramatic increase in due to reduced vertical mixing between Northern and Southern Source waters in the LGM Atlantic. In the second part of the talk I will explain some new GMC modeling work to investigate how Southern Source waters could have become more dense and volumetrically more important than Northern Source waters at the LGM, and how this would mean that they mix less. The essence of this idea comes down to the statement that 'Cooling NADW makes AABW saltier'. Finally I will try to show when in the decent into the LGM from the last interglacial some key climate and deep ocean reorganizations occurred. The MIS 5/4 boundary becomes very important in this analysis.