Black Sea subsurface temperature anomaly

'''DEFINITION'''

The subsurface temperature anomaly (T') is the average temperature (T) of a given year at a specific depth minus the reference temperature (<T>) at the same depth. {{su|p=y|b=k}}T'={{su|p=y|b=k}}T-{{su|p=y|b=k}}<T>. The superscripts y and subscript k respectively indicate the specific year and depth. The reference is the time-averaged temperature computed from 1993 to 2014 using the own reanalysis results.

'''CONTEXT'''

The temperature anomaly describes more accurately the Black Sea temperature variability as compared to the absolute temperature, so that the anomalies can provide a more valuable comparison between different ocean depths along the time. A positive anomaly means that the temperature at a specific time is warmer than the reference temperature, whereas a negative anomaly indicates a cooler temperature with respect to the reference one. The reference temperature is usually the average temperature calculated from a long period of time, by utilizing model results as reanalysis or observations. The anomalies can also provide key information about the temperature trends over time.

'''CMEMS KEY FINDINGS'''

The Black Sea Physics Reanalysis shows in general positive temperature anomalies from the surface down to layer 500 m, during period of time 2005-2017. The replenishment of the Cold Intermediate Layer (CIL) at depth 50-70 m in the winter months of 2006, 2012 and 2017 is also well represented. These years are known to be anomalously cold during winter year and freezing over the north part was observed."