Abstract

Abstract. Sea surface temperature (SST) has been obtained from a variety of different platforms, instruments and depths over the past 150 yr. Modern-day platforms include ships, moored and drifting buoys and satellites. Shipboard methods include temperature measurement of seawater sampled by bucket and flowing through engine cooling water intakes. Here I review SST measurement methods, studies analysing shipboard methods by field or lab experiment and adjustments applied to historical SST datasets to account for variable methods. In general, bucket temperatures have been found to average a few tenths of a °C cooler than simultaneous engine intake temperatures. Field and lab experiments demonstrate that cooling of bucket samples prior to measurement provides a plausible explanation for negative average bucket-intake differences. These can also be credibly attributed to systematic errors in intake temperatures, which have been found to average overly-warm by >0.5 °C on some vessels. However, the precise origin of non-zero average bucket-intake differences reported in field studies is often unclear, given that additional temperatures to those from the buckets and intakes have rarely been obtained. Supplementary accurate in situ temperatures are required to reveal individual errors in bucket and intake temperatures, and the role of near-surface temperature gradients. There is a need for further field experiments of the type reported in Part 2 to address this and other limitations of previous studies.

Highlights

  • Sea surface temperature (SST) is a fundamental geophysical parameter

  • SST observations are used in climate change detection, as a boundary condition for atmosphere-only models and to diagnose the phase of the El Nino–Southern Oscillation (ENSO)

  • Brooks (1926) compared tin bucket and engine intake temperatures collected aboard the Canadian Pacific steamship RMS Empress of Britain on a cruise between New York and the West Indies in February and March 1924

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Summary

Introduction

Sea surface temperature (SST) is a fundamental geophysical parameter. SST observations are used in climate change detection, as a boundary condition for atmosphere-only models and to diagnose the phase of the El Nino–Southern Oscillation (ENSO). The importance of SST to climate science is reflected in its designation as an Essential Climate Variable of the Global Climate Observing System. I review methods of SST measurement, field and lab analyses of shipboard methods and adjustments applied to historical SST datasets to reduce heterogeneity generated by variable methods. Adjustments developed for bucket and engine cooling water intake temperatures are described in Sect.

History of SST measurement
Bucket-intake temperature comparisons
Canvas bucket experiments by the Sea Education Association
Field comparisons of different bucket types
Wind tunnel experiments
Bucket and engine intake temperature adjustments
Exposure time
Findings
Synthesis and conclusions
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