Research Interests

Aerial Infrared Measurements of Sea Surface Temperature

We are currently using an infrared camera mounted on a small plane for measurements of sea surface temperature with high spatial resolution of 1-10 m. Mapping of an area of 15 km2 takes 30 min; the precision is 0.07oC. The instrument is used for rapid sampling of coastal eddies and fronts and is used to guide hydrographic in situ measurements. Starting in fall, hyperspectral measurements will be taken simultaneously in order to determine distribution and abundance of algae groups, sediments, or pollutants.

Rapid Hydrographic Measurements with a Towed Instrument Array

In order to capture short-lived small-scale oceanic eddies and fronts, we have developed a towed temperature-depth array with sensors at multiple depths. In field tests, it has been towed at speeds > 12 kt, allowing to measure the evolution of rapidly evolving eddies on scales of 0.5-10 km. Salinity and fluorescence measurements will be added.

Submesoscale Fronts, Eddies & Filaments

Submesoscale eddies and fronts are a likely route for energy transport from the large-scale ocean circulation to turbulence. Furthermore, they are closely linked to biogeochemical cycles. This is, for example, visible in ocean color and sea surface temperature in the upwelling regime off the coast of California, but also in mid-ocean eddies. Submesoscale features are very transient in nature, have a life time of several hours to a few days and spatial scales of < 10 km. Only few measurements exist on these scales. To confirm model results and improve parameterizations we are using quasi-synoptic aerial measurements of SST and ocean color from a small aircraft in combination with towed hydrographic in situ instrumentation.

Rogue Waves

Rogue Waves are unexpected waves that are more than twice as high as the significant wave height and can be extremely destructive for vessels or off-shore platforms. The coastal ocean offers a natural laboratory to study the formation of these waves, especially in areas of wave-current interaction. We are currently investigating several data sets and video footage to study the likelihood of rogue wave occurrence. It is planned to use a WaMoS wave radar to study the formation, and evolution of these waves.

Air-Sea Gas Exchange

The understanding of air-sea gas exchange is important for the coastal and global ocean (e.g. oxygen depletion, greenhouse effect). Direct bubble measurements are combined with indirect measurements of dissolved gases, which allows one to use dissolved gas concentrations as “fingerprint” of the entrainment mechanisms by utilizing the different physical and chemical properties of the gases. For this, especially the noble gases are of importance as they are not connected to biogeochemical cycles. To collect accurate long-term time-series measurements of all noble gases a Noble Gas Sampler (designed by D. Lott & W. Jenkins, WHOI) has been further developed and deployed off Bermuda. The results will be used for an improved and more physical parameterization of air-sea gas exchange that can be used by the global and coastal modeling community. For this purpose, a “bulk model” of gas bubble behavior was developed.

Flow-Topography Interaction & Tidal Fronts

The Fraser Estuary, BC, Canada, is a region of pronounced flow-topography interaction. Several tidal fronts develop around the islands of Haro Strait due to the strong tidal currents. Measurements were carried out during three research cruises with CCGS Vector in the tidal fronts at Stuart Island, Battleship Island, and Boundary Pass. Special attention was given to the strong hydraulic flow over a sharp sill at B oundar y Pass that proved to be of importance for the gas ventilation of intermediate water in the Strait of Georgia – a process that may be of significance to many estuaries with strong tidal currents. The flow over the sill is characterized by an arrested upper layer and intense detrainment of dense fluid with mixing rates of up to 60%. (Details)

Extreme Tidal Environments

Brief measurements of sea surface elevation, currents, and energy dissipation have been carried out in the extreme tidal environments of British Columbia, Canada (Dent, Arran, and Nakwakto Rapids). (Details)

Wave-Current Interaction

Tidal fronts are an area of intense wave-current interaction causing wave breaking even at low wind speeds. A model of wave energy dissipation in these fronts has been developed. Tidal fronts may also serve as a natural laboratory for understanding the formation of rogue waves. (Details)

Strait of Gibraltar

Extensive ship-board measurements of hydrography and currents were carried out in the Strait of Gibraltar as part of the international EU-project CANIGO (Canary Island Azores Gibraltar Observations; Uwe Send, IfM Kiel). A newly developed tidal inverse model provided accurate transport estimates through the Strait. These results were also used as comparison for acoustical tomography measurements during the same experiments. The work also focused on the dynamics of the hydraulically controlled exchange flow. (Details)

Bottom Water Formation in the Red Sea

The Gulf of Aqaba respresents an important source of bottom water in the Red Sea. This was shown in February 1999 by hydrographic ship-board measurements in combination with an analysis of the chlorofluorocarbon component CFC-12. (Details)

Physical-Biological Interaction

The coastal ocean is an area of strong interaction of biological and physical processes. A prime example is the entrance of the Saguenay Fjord, Quebec, Canada, where krill and fish distributions are greatly influenced by the strong tidal currents of a sill flow. An interdisciplinary project has been carried out in collaboration with collegues from UQAR/IML (Y. Simard, F. Saucier), and WHOI (W. Jenkins).