Casimir de Lavergne - Abyssal ocean overturning shaped by seafloor distribution

Event type: 
Seminar
Date: 
22 November 2017
Time: 
2.00pm - 3.00pm
Location: 

Climate Change Research Centre, Seminar Room, Mathews Building 4th floor, UNSW, Sydney

Presenter: 
Casimir de Lavergne
School of Mathematics and Statistics, UNSW
Host: 
Climate Change Research Centre, UNSW

The itinerary of dense waters from the surface high latitudes to the ocean abyss and back to the air-sea interface determines in large part the ocean’s ability to store carbon and heat on timescales exceeding a century. In this talk, using water mass transformation scenarios and maps of the radiocarbon content of seawater, I will show that the depth distribution of seafloor north of 30ºS compels dense southern-origin waters to flow north below 4 km depth and to return south predominantly deeper than 2.5 km. Unless ventilated from the north, the overlying mid-depths (1-2.5 km) host comparatively weak mean meridional flow. The results highlight a fundamental relationship between basin and circulation geometries, helping to constrain the past and present structure of the abyssal ocean circulation.

Biography: Casimir de Lavergne is a research associate working with Trevor McDougall at the School of Mathematics and Statistics (UNSW). His research focuses on the role of the deep and polar oceans in climate. Among his contributions feature studies of dense water formation in the Southern Ocean, Antarctic sea ice trends and water-mass transformation processes in the abyssal ocean. In his most recent work, he assesses the influence of seafloor geometry on deep ocean ventilation, using observations and theory.