Map of the week - Sea surface temperature anomalies

An article published in The Guardian on the 4^th of March 2019[1] exposes the alarming effects of global warming on sea-life but also on humanity, which relies on the oceans for many vital needs such as food and oxygen.

Titled “Heatwaves sweeping oceans ‘like wildfires’, scientists reveal”, the text by journalist Damian Carrington mentions that ocean heatwaves have become far more frequent in recent years resulting in the loss of foundation species critical to life in the oceans, like seagrass meadows or coral reefs.

Our “Map of the week” on sea surface temperature anomalies presents data from the year 2015 that share the same conclusion as the article:  temperatures are rising in many oceans and seas. Sea surface temperature (SST) is the temperature of the water close to the sea surface[2]. An anomaly is the deviation from the average condition, which can be in two directions (colder or warmer). The map shows positive anomalies (above zero) in orange colour in most of the regions of European seas and oceans, which reveals the gradual overall heating of the oceans.

Some SST anomalies are transient, one-off, events while others are more regular with longer-term effects such as in the case of the El Niño and La Niña climate cycles[3]. These cycles are fluctuations in temperature between the ocean and atmosphere in the east-central Equatorial Pacific last nine to twelve months and can occur on average every two to seven years. These cycles can also affect global weather and climate patterns. This includes the North Atlantic Oscillation (NAO), a large-scale weather phenomenon based on atmospheric pressure changes between the Azores and Iceland, that can affect SST, sea level and sea life. SST anomalies that persist over many years can be signals of regional or global climate change.

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