Eddy- and wind-sustained moderate primary productivity in the temperate East Sea (Sea of Japan)

Abstract

As part of the Dokdo East Sea Time Series Studies (DETS) in the East/Japan Sea, a DETS buoy system was moored on the 130 m deep continental shelf off the Dok Islets in the central part of the East Sea. Chlorophyll <i>a</i> concentrations in the surface water observed by the DETS buoy system exhibited low-frequency bimodal variations in the annual chlorophyll <i>a</i> concentration due to a spring phytoplankton bloom and a smaller fall bloom. In addition, between late spring and early fall when the water column is stratified, frequent low-concentration maxima occurred, which appear to have been triggered by the injection of nutrient-rich subsurface water to the sunlit surface water. The primary productivity in the nutrient-depleted surface ocean was found to be enhanced by subsurface water upwelling where the wind and water move in the same direction as the mesoscale eddy. New observations in the East/Japan Sea based on time-series measurements of chlorophyll <i>a</i>, wind, and other oceanographic variables at fixed sites in the center of the sea and using satellite measurements reveal that the vertical movement of water caused by wind-eddy interactions depends on the relative angle between the wind and the water current. The wind-eddy interaction appears to contribute to the unusually high primary productivity in the region where it was often sustained by the long-lived warm and cold eddies

Satellite-Observed Chlorophyll-a Concentration Variability and Its Relation to Physical Environmental Changes in the East Sea (Japan Sea) from 2003 to 2015

“…The consistent time series data of chl-a over a decade is valuable for evaluating annual dynamics of chl-a and its spatio-temporal variability throughout the EJS from the coastal area to the offshore. The EJS experiences bimodal phytoplankton blooms, which are typical in other temperate seas (Nagata 1994;Ishizaka et al 1997;Kim et al 2000;Yamada et al 2004Yamada et al , 2005Hong et al 2013;Jo et al 2014;Joo et al 2014). The spring bloom in the EJS generally begins in the south and propagates northward.…”

Summertime episodic chlorophyll &lt;i&gt;a&lt;/i&gt; blooms near the east coast of the Korean Peninsula

“…During summer, most rivers in the region become flooded and discharge large volumes of freshwater into the adjacent marginal seas, including the East Sea (Sea of Japan), Yellow Sea and East China Sea (Bae et al, 2008;Kong et al, Y.-T Son et al: Summertime episodic chlorophyll a blooms near the east coast of the Korean Peninsula 2013). Chl a distribution in the southwestern East Sea off the east coast of the Korean Peninsula has been found to be associated with physical processes at mesoscale or larger scales, including spring and fall blooms that have been detected using satellite ocean color data, data from short-duration ship surveys (Hyun et al, 2008;Kang et al, 2004) and time-series data collected continuously from moored buoys (Hong et al, 2013;Son et al, 2014). Despite wide-range images available from geostationary and polar-orbit satellite ocean color remote sensing (Yoo and Kim, 2004;Son et al, 2014;Hyun et al, 2008;Kim et al, 2011), phytoplankton blooms observed over several days to weeks near the coast, particularly during the well-stratified summer season, have rarely been examined.…”

“…Chl a distribution in the southwestern East Sea off the east coast of the Korean Peninsula has been found to be associated with physical processes at mesoscale or larger scales, including spring and fall blooms that have been detected using satellite ocean color data, data from short-duration ship surveys (Hyun et al, 2008;Kang et al, 2004) and time-series data collected continuously from moored buoys (Hong et al, 2013;Son et al, 2014). Despite wide-range images available from geostationary and polar-orbit satellite ocean color remote sensing (Yoo and Kim, 2004;Son et al, 2014;Hyun et al, 2008;Kim et al, 2011), phytoplankton blooms observed over several days to weeks near the coast, particularly during the well-stratified summer season, have rarely been examined. Thus, we aimed to address the episodic bloom events in summer and investigated the effects of river plumes on Chl a distribution near and away from the east coast of the Korean Peninsula.…”

Summer-time episodic chlorophyll-a blooms near east coast of Korea

“…During summer, most rivers in the region become flooded and discharge large volumes of freshwater into the adjacent marginal seas, including the East Sea (Japan Sea), Yellow Sea, and East China Sea (Bae et al, 2008;Kong et al, 2013). Chl a distribution in the southwestern East Sea off the east coast of Korea has been examined, and found to be associated with physical processes at mesoscale or larger scales, including spring and fall blooms that have been detected using satellite ocean color data, data from limited short-duration ship surveys (Hyun et al, 2008;Kang et al, 2004), and time-series data collected continuously from moored buoys (Hong et al, 2013;Son et al, 2014).…”