In physics, the word “dynamics” refers to studies of motion caused by forces. Both physical oceanography and atmospheric dynamics are branches of physics that focus on fluid dynamics at geophysical scales, sometimes referred to as geophysical fluid dynamics (GFD). Broadly, GFD refers to the study of fluid motion on planetary scales. In the case of Earth, it is the study of the circulation in both ocean and atmosphere. The circulation includes ocean currents, atmospheric wind systems, waves in both fluids and a continuum of motions down to those of the small-scale turbulence that acts to mix the fluids. The net sum of these motions contributes to predictions of our weather, our past and present climate as well changes to future climates. These studies contribute, at a very fundamental level, to both weather and climate predictions.
GFD is at its core an application of fundamental physical laws and principles such as the conservation of mass, momentum, and energy. The great complication of GFD is that it encompasses spatial scales from those of small-scale turbulence (mm to cm) to global scale (10s of thousands of km) and time scales from seconds (in the case of turbulence) to days (weather) to decades (climate change) to millennia (past climates). Not only are different processes dominant at different time and space scales, but all of the processes also interact across the spectrum of space and time. The vast range of scales precludes adequate observation and numerical simulation, confounding predictability.
Since the motions at the smallest scales of GFD influence the largest scales, it is important to understand how mixing occurs in both ocean and atmosphere and at what rate mixing proceeds. This is especially needed for the development of accurate numerical models of the ocean.
Mixing occurs at molecular scales by diffusion across gradients. In the case of the mixing of heat, mixing is across thermal gradients. Mixing is enhanced by turbulence, which represents the chaotic motions at the smallest scales and which increases small scale gradients by many orders of magnitude. So the study of mixing in the ocean is intrinsically linked to studies of turbulence and how turbulence is initiated.
Our studies focus on making measurements of turbulence in a wide range of geographic regions and dynamical regimes from the sea surface to the sea floor and from high latitudes to the tropics. From these measurements, we try to infer how the mixing of mass, momentum, heat, etc. affect the ocean’s circulation and how it communicates with the atmosphere above. Some of these studies and some of the instrumentation we have developed to execute these studies are briefly discussed in these web pages.
Research in Ocean Mixing at CEOAS is funded primarily by