Water temperature and salinity data from southern elephant seals from Marion Island

Over the last decade, several hundred seals have been equipped with conductivity-temperature-depth sensors in the Southern Ocean for both biological and physical oceanographic studies. A calibrated collection of seal-derived hydrographic data is now available, consisting of more than 165,000 profiles. The value of these hydrographic data within the existing Southern Ocean observing system is demonstrated herein by conducting two state estimation experiments, differing only in the use or not of seal data to constrain the system. Including seal-derived data substantially modifies the estimated surface mixedlayer properties and circulation patterns within and south of the Antarctic Circumpolar Current. Agreement with independent satellite observations of sea ice concentration is improved, especially along the East Antarctic shelf. Instrumented animals efficiently reduce a critical observational gap, and their contribution to monitoring polar climate variability will continue to grow as data accuracy and spatial coverage increase.

Nd-isotope ratios of Cretaceous sediment samples

The role that meridional overturning circulation (MOC) patterns played in poleward heat transport during the extreme warmth of the Early to Late Cretaceous is a fundamental and unresolved question in climate dynamics. In order to address this question we must determine where deep waters formed, and how they may have circulated during periods of extreme warmth. Here we present late Albian through Maastrichtian (105 to 65 Ma) Nd isotope records from Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) sites in the proto-Indian Ocean and the tropical Pacific. Comparison of these data with previously published records indicates deep-water formation in the Indian sector of the Southern Ocean began at least ?105 Ma, extending the record of high-latitude convection back into the Early Cretaceous prior to the peak warmth of the mid-Cretaceous. The growing body of data supports a mode of MOC in part characterized by high-latitude downwelling during the peak of greenhouse warmth of the Mesozoic and Cenozoic. However, this mode of MOC likely was characterized by numerous locations of deep convection that were regionally important, but not significant in terms of a globally overturning circulation due to paleogeographic and bathymetric barriers.