Abstract
Changes of high-latitude freshwater content (FWC) play an important role in shaping the variability of polar oceans. FWC is defined as depth-integrated departure of salinity from a reference salinity Sref divided by this Sref . A constant Sref is often used for high-latitude FWC estimates. Here it is argued that for analyzing FWC spatiotemporal changes the use of local mean Sref is a better choice. Analysis of 2007 FWC anomalies in the 25–75 m layer demonstrated, for example, that the choice of Sref = 34.8 (which is often used in climate studies) leads to FWC spatial anomalies exaggerated, on average, by ~0.6 m, which is a substantial fraction of total spatial FWC changes. The problem is aggravated in areas where the difference between the local Sref and Sref = 34.8 is greater. Thus, it is concluded that using climatological mean salinities as Sref provides superior estimates of spatiotemporal Arctic Ocean FWC changes.
Highlights
High-latitude regions play a special role in shaping variability in sub-polar oceans through regulating convection in the Labrador and Greenland seas via freshwater exchanges [e. g. 1, 2]
Using 2007 observational data as an example, this paper demonstrates substantial differences between 25–75 m Arctic Ocean mean and anomalous freshwater content (FWC) calculated using local mean Sref and the constant Sref = 34.8, which is often used in climate studies
Estimates based on the latter Sref may be useful in illustrating very different FWC in the upper and lower layers of the Arctic Ocean or the fresher state of the Polar Basin compared with sub-polar oceans
Summary
Changes of high-latitude freshwater content (FWC) play an important role in shaping the variability of polar oceans. FWC is defined as depth-integrated departure of salinity from a reference salinity Sref divided by this Sref. A constant Sref is often used for high-latitude FWC estimates. It is argued that for analyzing FWC spatiotemporal changes the use of local mean Sref is a better choice. The problem is aggravated in areas where the difference between the local Sref and Sref = 34.8 is greater. It is concluded that using climatological mean salinities as Sref provides superior estimates of spatiotemporal Arctic Ocean FWC changes. For Citation: Polyakov I.V. The effect of using local mean versus constant reference salinity to estimate Arctic Ocean freshwater content changes.
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