Abstract
During the winter of 2013–2014, the averaged tide gauge (TG) coastal sea level (CSL) anomaly north of 40°N was a record low of −107 mm for the period of 1948–2016. Statistical analysis indicates that this large drop was a once-in-a-century event and closely related to an unusual ocean warming event known as “The Blob”. The Blob developed in the NE Pacific during the winter of 2013–2014. Both the Blob and record-low CSL can be attributed to wind changes associated with an unusually high sea level pressure (SLP) pattern over the NE Pacific. The anomalous local longshore winds induced by the positive SLP anomalies caused strong offshore Ekman transport along the coast of NE Pacific, thereby leading to the record-low CSL. In addition, the steric sea level changes also contributed a significant part (17%) to the record-low CSL. The Pacific Decadal Oscillation (PDO), as the primary variability mode in the NE Pacific on decadal time scales, did not contribute to the emergence of this extreme CSL event.
Highlights
Coastal sea levels (CSL) manifest important variability and changes of the coupled ocean-atmosphere system
We find that large-scale climate modes did not contribute to the emergence of the record-low coastal sea level (CSL) in the NE Pacific in winter 2013–2014
The North Pacific Gyre Oscillation (NPGO), El Niño and Pacific Decadal Oscillation (PDO) can be linked by the evolution of the positive sea level pressure (SLP) anomaly over the NE Pacific for the winter of 2013–2014 and the following two winters[10,24,25,26,27]
Summary
Coastal sea levels (CSL) manifest important variability and changes of the coupled ocean-atmosphere system. Thompson et al.[6] used the method of multiple linear regression to examine the relative contributions from remote equatorial wind stress, local longshore wind stress, and local wind stress curl, and suggested that the decreased rate of sea level rise along the coast of NE Pacific from 1992–2010 is primarily due to the ocean’s response to the strengthened trade winds, with longshore wind stress becoming important to CSL trends from 37°N to 48°N Most of these studies were concerned about the CSL trends in the NE Pacific over the past three decades, but extreme year-to-year changes have received less attention. The cause for this extreme CSL anomaly and the role of large-scale climate modes are investigated
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