Possible link between temperatures in the seashore and open ocean waters of Peru identified by using new seashore water data

Abstract

The linkage between environmental conditions in the coastal ocean and the open sea varies greatly by region. It is important to clarify, on an area-by-area basis, what coastal monitoring information reveals about the open ocean and how much predictive information for the open ocean may be applicable to the coastal ocean. The Pacific Ocean off the coast of Peru is a monitoring area for the El Niño/La Niña, an oceanic–atmospheric phenomenon of global importance. However, there are not many reliable data along the Peruvian coast. We deployed a network of 6 logger sites along the Peruvian coast during 2017–2020 and compiled a useful, high-resolution dataset of water temperatures. We examined a possible link between temperatures in the coastal waters of Peru and the open sea by comparing the new dataset with historical temperatures in the open ocean. We confirmed that monthly mean anomalies of seashore water temperatures in coastal Peru were strongly correlated with those of open ocean sea surface temperatures. With one exception, the correlation coefficients ranged from 0.80 to 0.92 and were significant at p < 0.01. This result suggested that data obtained from monitoring along the Pacific coast of Peru could be used to indicate the state of the open ocean and that El Niño forecasts for the open ocean could be applied to coastal forecasting as well. Spectral analysis revealed that the periods of changes of seashore water temperature peaked at 80 and 120 days in the region north of 5° S. This result suggested that coastal monitoring might capture intraseasonal dynamics of equatorial Kelvin waves. The absence of clear peaks south of 5° S implied that equatorial wave energy did not penetrate far into off-equatorial regions along the Peruvian coast on intraseasonal timescales.