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Extreme temperatures are the new normal

Climate change is changing our planet. This also applies to the world’s oceans: for more than half of our oceans, repeated heat waves are now normal. This means that the temperature of the affected sea areas is now permanently in ranges that were classified as rare heat waves 100 years ago. The South Atlantic, the Arctic Ocean and the Indian Ocean are particularly affected.

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Photo: The Atlantic Ocean, Milan Boers, Flickr, CC BY-SA 2.0

Historical data show changes in the seas

The fact that the oceans are not spared from constant climate change and are warming up is not surprising. The world’s oceans are an important climate buffer and, in this capacity, absorb a significant part of the heat caused by anthropogenic climate change. This has repeatedly led to record values ​​for several years now. In addition, there is an increase in marine heat waves, which are affecting entire ecosystems.

A team led by Kisei Tanaka from the Monterey Bay Aquarium in California and Kyle Van Houtan from Duke University have now investigated the occurrence of extreme heat phases in the oceans. This was based on measurement data from 1920 to 2019, which the researchers compared with historical data from the period between 1870 and 1919. The team paid particular attention to the trend towards extreme values. The extreme values ​​were considered to be the top two percent of the measured values.

In their study, the scientists determined when and how often these limit values ​​were exceeded for each of the seven seas and each sub-region including national sovereign waters. “We have also determined from which year at least half of a sea has remained permanently above these limit values“, according to the team.

Oceans are getting warmer

As a result, the researchers found that temperatures that were previously considered extreme are now completely normal in many parts of the world’s oceans. “Today, 57 percent of the global sea surface has permanent temperatures that more than a hundred years ago were still considered rare heat events that only occur once every 50 years“, says the study.

It happened for the first time in 2014 that all oceans crossed the threshold of their historical limits. In individual areas, however, the change from extreme values ​​to normality took place much earlier – in the South Atlantic this development has even been observed since 1998.

The researchers see their results as a sign of how clearly climate change is affecting the oceans in particular. “These drastic changes are another wake-up call. This change is happening now and is accelerating. This condition and further increases in heat extremes could push many ecosystems beyond their tolerance limits“, says Van Houtan.

Humans are also affected

In addition to corals, some of which are extremely sensitive to excessive water temperatures, and the marine ecosystems, the changes also affect people. As Van Houtan explains, important ecological services also suffer with the changes in ecosystems associated with the rise in temperature. This includes, for example, the protection of coastal areas from high tides and waves, the effect of the oceans as a climate buffer and the production of fish and seafood.

via Monterey Bay Aquarium

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Reference-www.trendsderzukunft.de

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