Atmosphere-ocean energy and nitrous oxide exchange and mixed layer dynamics in the Caribbean Sea and neighboring Atlantic Ocean.

摘要

The air-sea fluxes of energy and nitrous oxide (N2O) in oceanic waters of the Caribbean Sea and neighboring Atlantic Ocean (10°N--24°N, 48°W--88°W) were studied. These fluxes were estimated using parameterization formulas and five gas exchange turbulent models applied to 1980--1995 COADS data. The region was divided in four subregions that exhibit different patterns of wind speed (W) and sea surface temperature ( Ts), the main parameters controlling regional heat fluxes. Monthly averages on latitude bands of 2° width and time spectral analysis were obtained for Ts, air surface temperature (Ta), W, relative humidity (RH), cloud cover ( C) and sea level pressure (P). The spatial and temporal behavior of these climate parameters reveals that oceanic regions mainly have annual variation, while coastal areas show biannual variation.; The spatial distribution of Ts revealed that the Caribbean Sea is warmer than the Atlantic Ocean with a consistent difference of about 0.5°C--0.75°C throughout the year. Winds affect Ts at coastal areas inducing upwelling in the central (CC) and eastern Caribbean (EC) subregions. The southern part (11°N--13°N) of these subregions is cooler (∼0.5°C) than the rest of the Caribbean from January to March. The temperature difference between those latitudes and higher latitudes (24°N) increases up to about 1°C in July when wind speed strengthens. This strengthening is associated to the meridional gradient of P. During July at CC, the highest gradient (0.58 mb/°lat) simultaneously occurs with the highest wind speeds. At low latitudes (11°N--15°N), C presents a maximum during June, simultaneously with a minimum in the solar heat flux. Thermal stability (dTs = Ts-Ta ) is of significant importance in the sea-atmosphere energy exchange. Over the region, a high correlation coefficient (-0.92) was found between net heat flux and dTs. This parameter also controls the mixed layer depth, except in February and July when wind effects become important.; The N2O fluxes were similar among the different models, yielding a mean regional production of 0.1229 tera g/year, about 1%--3% of N 2O global emissions. This production is moderate considering that the study region represents 1.705% of the global oceanic area. There is no clear correlation between N2O fluxes and W, however these appear to be more influenced by surface salinity changes. From June to December, the eastern part of the region (68W--48W) shows slightly higher emissions, likely associated to Orinoco and Amazon River intrusions which spread over a large portion of the Eastern Caribbean Sea during September and October.