Knowledge of coastal currents can help commercial fishing and shipping industries, search-and-rescue operations, and those tasked with monitoring marine ecosystem health. Thus, any sudden changes in the behavior of currents could affect economies, safety, and environmental management.
Recently, scientists have discovered a seasonal anomaly of an ocean current off the Korean Peninsula—the current, which was thought to only flow north, reverses its course in the summer. In their recent paper, Park et al. confirmed these observations and offered an explanation for this anomalous behavior.
The switching current occurs inshore of the East Korea Warm Current in the Sea of Japan (East Sea), which flows poleward for most of the year. The researchers observed a robust current reversal between 2007 and 2012 that sent it flowing down toward the equator from June to September.
To find the source driving the current reversal, the scientists measured current flow, temperature, salinity, and wind in the region. The data revealed that the anomaly is caused by changes in wind patterns. Specifically, when spatially varying wind blows over the surface of the ocean, it produces spatial density differences in the interior of the ocean, resulting in sharp changes in water pressure. The contrasts between wind-induced pressure highs and lows drive the reversed summer current.
The results of this reversed current can have an impact on the ecosystems in this area. The researchers noticed that warmer, fresher water is carried down by the southward summertime current, which potentially brings in more nutrients to the ecosystem and feeds the coastal food chain. Future research in this area will analyze how this summer current reversal impacts the biology of this area. (Geophysical Research Letters, doi:10.1002/2016GL069322, 2016)
—Alexandra Branscombe, Freelance Writer