Zhang Jia-Zhong, Baringer Molly O, Fischer Charles J, Hooper V James A
NOAA, Ocean Chemistry and Ecosystems Division, Atlantic Oceanographic and Meteorological Laboratory, Miami, FL, 33149, USA.
NOAA, Physical Oceanography Division, Atlantic Oceanographic and Meteorological Laboratory, Miami, FL, 33149, USA.
Sci Rep. 2017 Nov 23;7(1):16098. doi: 10.1038/s41598-017-15853-0.
A recent hydrographic survey of the Florida Current at 27°N revealed an enhanced upward flux of nutrients along the Florida coast. Geostrophic flow of the Gulf Stream through the narrow Florida Straits causes an uplift of the nutricline toward its western edge, shoaling the mixed layers into the base of the euphotic zone. At a nearshore station, nitrate, phosphate, and silicate concentrations reached 19, 1.4, and 10 µM, respectively, at a water depth of 27 m. Furthermore, nutrient vertical gradients below the mixed layer increased with decreasing seafloor depth toward the Florida coast. The estimated vertical eddy diffusive nutrient fluxes across diapycnal surfaces reached 0.40-83.7, 0.03-6.24, and 0.24-45.5 mmol m d for nitrate, phosphate, and silicate, respectively, along the shore. Estimated fluxes span a wide range due to the range of diffusivity measured. The lower end of estimated fluxes are comparable to open ocean values, but higher end of estimates are two orders of magnitude greater than those observed in open ocean. The diapycnal nutrient fluxes declined rapidly offshore as a result of decreasing vertical gradients of nutrient concentration.
最近在北纬27°对佛罗里达洋流进行的水文调查显示，佛罗里达海岸沿线营养物质的向上通量有所增加。湾流通过狭窄的佛罗里达海峡的地转流导致营养跃层向其西边缘隆起，使混合层变浅至真光层底部。在一个近岸站点，水深27米处的硝酸盐、磷酸盐和硅酸盐浓度分别达到19、1.4和10微摩尔/升。此外，混合层以下营养物质的垂直梯度随着靠近佛罗里达海岸海底深度的减小而增加。沿岸边，估计穿过斜压面的垂直涡动扩散营养通量，硝酸盐、磷酸盐和硅酸盐分别达到0.40 - 83.7、0.03 - 6.24和0.24 - 45.5毫摩尔/(米²·天)。由于测量的扩散率范围，估计通量跨度很大。估计通量的下限与开阔海洋的值相当，但估计通量的上限比在开阔海洋中观测到的值大两个数量级。由于营养物质浓度垂直梯度的减小，斜压营养通量在离岸方向迅速下降。
