|Title||Sea surface temperature variability at the Scripps Institution of Oceanography Pier|
|Publication Type||Journal Article|
|Year of Publication||2014|
|Authors||Checkley DM, Lindegren M|
|Journal||Journal of Physical Oceanography|
|Type of Article||Article|
|Keywords||california; climate; fluctuations; north pacific; ocean; Pacific sardine; regime shifts; rip currents; sardine sardinops-sagax; southern; stock-recruit|
Sea surface temperature (SST) has been measured from near the end of the Scripps Institution of Oceanography (SIO) pier daily since 1916. It is one of the world's longest instrumental time series of SST. It is widely used in studies of climate and marine ecosystems and in fisheries management. The authors hypothesized that a discontinuity exists in 1988, when the old pier was replaced with the present pier. A regression of annual-mean SST at SIO (SSTSIO) on the Pacific decadal oscillation index for 1916-87 was used to predict annual-mean SST (SSTSIO,PDO) for 1916-present. The residual (ResSST(SIO) = SSTSIO - SSTSIO,PDO) time series shows a positive discontinuity in 1988, when the present SIO pier was first used to measure SSTSIO. No discontinuity in 1988 was observed for ResSST at 12 other shore stations or in nearby waters. Use of the first principal component of other shore station time series of annual-mean SST as the predictor yields similar results. SSTSIO measured over 3 days shows a diel cycle and short-term variability consistent with rip current transport of warm surf-zone water to the end of the SIO pier. This study hypothesizes that rip current transport increased with the change from the old to the present pier and contributed to the observed discontinuity in SIO pier SST. The authors estimate an artifact of about +0.45 degrees C due to both rapid (1988 pier change) and gradual processes. Adjusting the SIO pier SST time series for this artifact reduces the long-term trend from +1.1 degrees to +0.6 degrees C century(-1), consistent with the global rate of change of SST over the past century.
The researchers attributed a greater increase in sea-surface temperature recorded at the pier than the global average increase over this period in part to the replacement of the institution’s original pier in 1988. That replacement contributed to an increase—what scientists call an artifact—of temperature taken thereafter. Adjusting the Scripps Pier sea-surface temperature record to account for this increase “reduces the long-term trend from +1.1°C/century to +0.6°C/century, consistent with the global rate of change of sea-surface temperature over the past century,” wrote Checkley and Lindegren in the paper recently published in the Journal of Physical Oceanography.