Publication Date:
2022-05-25
Description:
Author Posting. © American Meteorological Society, 2009. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 39 (2009): 2685-2710, doi:10.1175/2009JPO3980.1.
Description:
The aqueous thermal boundary layer near to the ocean surface, or skin layer, has thickness O(1 mm) and plays an important role in controlling the exchange of heat between the atmosphere and the ocean. Theoretical arguments and experimental measurements are used to investigate the dynamics of the skin layer under the influence of an upwelling flow, which is imposed in addition to free convection below a cooled water surface. Previous theories of straining flow in the skin layer are considered and a simple extension of a surface straining model is posed to describe the combination of turbulence and an upwelling flow. An additional theory is also proposed, conceptually based on the buoyancy-driven instability of a laminar straining flow cooled from above. In all three theories considered two distinct regimes are observed for different values of the Péclet number, which characterizes the ratio of advection to diffusion within the skin layer. For large Péclet numbers, the upwelling flow dominates and increases the free surface temperature, or skin temperature, to follow the scaling expected for a laminar straining flow. For small Péclet numbers, it is shown that any flow that is steady or varies over long time scales produces only a small change in skin temperature by direct straining of the skin layer. Experimental measurements demonstrate that a strong upwelling flow increases the skin temperature and suggest that the mean change in skin temperature with Péclet number is consistent with the theoretical trends for large Péclet number flow. However, all of the models considered consistently underpredict the measured skin temperature, both with and without an upwelling flow, possibly a result of surfactant effects not included in the models.
Description:
The work was initiated during
the Woods Hole Oceanographic Institution Geophysical
Fluid Dynamics Program, where AJW was supported by
a fellowship of the program. CC was supported by NSF
Grant OCE-82633900. JTF was supported in part by The
Penzance Endowed Fund in Support of Assistant Scientists.
CJZ was supported by NSF Grant OCE-0425395
and the Office of Naval Research Young Investigator
Program Grant N00014-04-1-0621. Additional funding
for this research came from the U.S. Office of Naval
Research through the Coupled Boundary Layer Air-Sea
Transfer Departmental Research Initiative (Grants
N00014-05-10090 and N00014-05-1-0036).
Keywords:
Sea/ocean surface
;
Sea surface temperature
;
Surface layer
;
Heat budgets
;
Model comparison
Repository Name:
Woods Hole Open Access Server
Type:
Article
Format:
application/pdf
Permalink
