Publication Date:
2022-05-26
Description:
Author Posting. © American Geophysical Union, 2009. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 114 (2009): C07020, doi:10.1029/2008JC004902.
Description:
The fate of particles in the mixed layer is of great relevance to the global carbon cycle as well as to the propagation of light in the sea. We conducted four manipulative field experiments called “Chalk-Ex” in which known quantities of uniform, calcium carbonate particles were injected into the surface mixed layer. Since the production term for these patches was known to high precision, the experimental design allowed us to focus on terms associated with particle loss. The mass of chalk in the patches was evaluated using the well-calibrated light-scattering properties of the chalk plus measurements from a variety of optical measurements and platforms. Patches were surveyed with a temporal resolution of hours over spatial scales of tens of kilometers. Our results demonstrated exponential loss of the chalk particles with time from the patches. There was little evidence for rapid sinking of the chalk. Instead, horizontal eddy diffusion appeared to be the major factor affecting the dispersion of the chalk to concentrations below the limits of detection. There was unequivocal evidence of subduction of the chalk along isopycnals and subsequent formation of thin layers. Shear dispersion is the most likely mechanism to explain these results. Calculations of horizontal eddy diffusivity were consistent with other mixed layer patch experiments. Our results provide insight into the importance of physics in the formation of subsurface particle maxima in the sea, as well as the importance of rapid coccolith production and critical patch size for maintenance of natural coccolithophore blooms in nature.
Description:
We would like to thank the Office of Naval
Research/Optical and Biological Oceanography Program for their support
of Chalk-Ex with awards N000140110042 (WMB) and N00014-01-1-0141
(AJP). Additional funding for this work came from ONR (N00014-05-1-
0111) and NASA (NNG04Gl11G, NNX08AC27G, NNG04HZ25C) to
W.M.B.
Keywords:
Calcium carbonate
;
PIC
;
Chalk
;
Coccoliths
;
Coccolithophores
;
Eddy diffusion
Repository Name:
Woods Hole Open Access Server
Type:
Article
Format:
application/pdf
Format:
text/plain
Format:
image/jpeg
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