Measurements of the Diurnal Warm Layer and Biologically-Induced Heating during the CIRENE Campaign

Woods Hole Oceanographic Institution, Woods Hole MA

Investigators

Abstract

Atmospheric convection in the Indian Ocean has a strong impact on the monsoon. During winter, the maximum amplitude of convection is located between the equator and 20 S, and is generally referred to as the Madden-Julian oscillation (MJO). Recent studies based on satellite data have shown that the intraseasonal activity in this region is associated with large sea surface temperature (SST) variability (up to 3 C), and it has been suggested that air-sea interaction plays an important role. Heretofore there have been only satellite data and numerical modelling used to investigate the variability in these regions. It is proposed to participate in a French Campaign the objective of which is to understand ocean-atmosphere coupling at the intraseasonal timescale in this region of the Indian Ocean, and to explain the mechanisms of the SST variability and its influence on the atmospheric evolution. Measurements will be made using the Air-Sea Interaction Profiler (ASIP), augmented with 5 Lagrangian floats, with 24-node temperature chains attached. ASIP, previsouly funded by the NSF Oceanographic Technology program, will provide profiles of temperature, conductivity, shear, fluorescence/turbidity, and PAR over the full depth of the mixed layer at sub-centimeter spatial resolution and repeat intervals of 5 minutes. This proposal will address the following fundamental problems: 1. the relative importance of local SST conditions and the diurnal cycle of the warm layer versus large scale atmospheric conditions 2. the biological contribution to heat trapping in the near-surface layer, and its role in the overall heat budget. The broader impacts of the objectives relate to climate change by addressing some of the issues pertinent to atmospheric convection in the Indian Ocean; the MJO interacts with the El Nino-Southern Oscillation, the monsoons, and extratropical weather, and therefore of global importance.