Clayton Sophie, Palevsky Hilary I, Thompson LuAnne, Quay Paul D
Department of Ocean and Earth Sciences Old Dominion University Norfolk VA USA.
Department of Earth and Environmental Sciences Boston College Boston MA USA.
J Geophys Res Oceans. 2021 Nov;126(11):e2021JC017782. doi: 10.1029/2021JC017782. Epub 2021 Nov 18.
The Kuroshio current separates from the Japanese coast to become the eastward flowing Kuroshio Extension (KE) characterized by a strong latitudinal density front, high levels of mesoscale (eddy) energy, and high chlorophyll (Chl). While satellite measurements of Chl show evidence of the impact of mesoscale eddies on the standing stock of phytoplankton, there have been very limited synoptic, spatially resolved in situ estimates of productivity in this region. Here, we present underway measurements of oxygen/argon supersaturation (ΔO/Ar), a tracer of net biological productivity, for the KE made in spring, summer, and early autumn. We find large seasonal differences in the relationships between ΔO/Ar, Chl, and sea level anomaly (SLA), a proxy for local thermocline depth deviations driven by mesoscale eddies derived from satellite observations. We show that the KE is a pronounced hotspot of high ΔO/Ar in spring, but corresponding surface Chl values are low and have no correlation with ΔO/Ar. In summer, there is a hotspot of productivity associated with the Oyashio front, where ΔO/Ar and Chl are strongly positively correlated. In autumn, ΔO/Ar and Chl are consistently low throughout the region and also positively correlated. By combining our analysis of the in situ ΔO/Ar data with complementary Argo, BGC-Argo, repeat hydrography, and SLA observations, we infer the combination of physical and biological controls that drive the observed distributions of ΔO/Ar and Chl. We find that the KE and Oyashio currents both act to supply nutrients laterally, fueling regions of high productivity in spring and summer, respectively.
黑潮从日本海岸分离后成为向东流动的黑潮延伸带（KE），其特征是存在强烈的纬向密度锋、高水平的中尺度（涡旋）能量和高叶绿素（Chl）含量。虽然卫星对叶绿素的测量显示了中尺度涡旋对浮游植物存量的影响，但该区域生产力的同步、空间分辨原位估计非常有限。在此，我们展示了在春季、夏季和初秋对黑潮延伸带进行的氧/氩过饱和度（ΔO/Ar）的现场测量，ΔO/Ar是净生物生产力的一个示踪指标。我们发现，在ΔO/Ar、Chl和海平面异常（SLA）之间的关系上存在很大的季节差异，SLA是由卫星观测得出的中尺度涡旋驱动的当地温跃层深度偏差的一个代理指标。我们表明，黑潮延伸带在春季是一个明显的高ΔO/Ar热点区域，但相应的表层Chl值较低，且与ΔO/Ar没有相关性。在夏季，存在一个与亲潮锋相关的生产力热点区域，在那里ΔO/Ar和Chl呈强烈正相关。在秋季，整个区域的ΔO/Ar和Chl一直较低，且也呈正相关。通过将我们对现场ΔO/Ar数据的分析与补充的Argo、BGC - Argo、重复水文测量和SLA观测相结合，我们推断出驱动观测到的ΔO/Ar和Chl分布的物理和生物控制因素的组合。我们发现，黑潮延伸带和亲潮都起到了横向供应营养物质的作用，分别为春季和夏季的高生产力区域提供养分。
