Research & Projects
GENTOO
(Gliders: Excellent New Tools for Observing the Ocean)
In January 2012 we will travel to the Weddell Sea to collect measurements of local currents that have global significance for ocean circulation, climate and krill ecology. Glider measurements will provide temporal coverage over an extended period with complementary shipboard measurements. We will assess changes in dense bottom water properties as well as its variability. GENTOO will develop and demonstrate the capability of ocean gliders to play a key role in future polar ocean observing systems.
GENTOO study region, Weddell Sea.
Southern Ocean Jets
Atmospheric and oceanic flows have both turbulent and wave-like properties that cause large-scale motions to organize into persistent, narrow zonal (east-west) jets. The Southern Ocean's Antarctic Circumpolar Current (ACC) is an important site of jet formation. Traditionally, the ACC was thought to have three circumpolar jets or fronts. However, the advent of satellite altimetry and high-resolution numerical models has indicated that the ACC is comprised of numerous narrow, filamentary structures that play a crucial role in regulating global heat and tracer transport. (Image courtesy of Andrew Coward, NOC Southampton).
ACC surface speed (OCCAM circulation model).
ADELIE (Antarctic Drifter Experiment:
Links to Isobaths and Ecosystems)
The Weddell Sea is responsible for the export of unique water properties to the global ocean. Surface waters originating along the eastern coast of the Antarctic Peninsula have been suggested as possible sources for large plankton blooms observed in the Southern Ocean. The Weddell Sea is also a key site of Antarctic Bottom Water (AABW) formation, which spreads to cover most of the ocean bottom. In 2007, the ADELIE project measured the narrow region where this source water leaves the Weddell Sea in unprecedented detail using surface drifters floats and hydrographic data.
ADELIE drifter trajectories.
Baroclinic turbulence in the ocean and atmosphere
In the atmosphere and ocean a poleward heat flux arises to balance heating at the equator and cooling at the poles. Because these environments are stratified and feel the Earth's rotation, the large-scale temperature or density gradients stored in this differential heating can store enormous amounts of potential energy. Baroclinic instability is the mechanism by which this energy is converted to kinetic energy in the form of mesoscale eddies or atmospheric storms (with length scales of 50 km and 1000 km respectively). Heat transport by these coherent structures make an important contribution to the global energy balance. Inclusion of these eddy fluxes in general circulation models (GCMs) is essential for producing accurate representations of the global climate.
Baroclinic turbulence over bumpy topography.
OSMOSIS (Ocean Surface Mixing, Ocean Sub-mesoscale Interaction Study)
The ocean surface boundary layer (OSBL) deepens in response to convective, wind and surface wave forcing, which produce three-dimensional turbulence that entrains denser water, deepening the mixed layer. The OSBL shoals in response to solar heating and to mesoscale and sub-mesoscale motions that adjust lateral buoyancy gradients into vertical stratification. In 2012 and 2013, a major observational effort will attempt to resolve the evolution of these surface dynamics over a full annual cycle. Observations will include a continuous time series of upper ocean temperature, salinity, chlorophyll and velocity obtained from ocean gliders.
Keep an eye on ocean color!
Ocean surface boundary layer physics.
Geophysical fluid dynamics laboratory experiments
Stratification and rotation play a major role in determining ocean circulation. Laboratory experiments often provide key insight into how buoyancy effects, due to both temperature and salinity in the ocean, give rise to motion and impact transport and mixing. Previous studies include convection, solidification, double diffusion and gravity currents. Ongoing work by Alan Jamieson (U. Cambridge) will consider the downstream evolution of dense plumes they flow along the continental margins. This work is in collaboration with the GENTOO project (see above).
Doubly diffusive thermohaline intrusion in the lab.