Exploring the Unprecedented Ocean Temperatures of 2023

Tuesday - July 11 2023, 03:36 UTC - 1 year ago

Ocean temperatures have been exceptionally high in the past year and a half since mid-March 2023. Global warming, El Niño, the decrease of human-produced aerosol emissions, and Arctic sea ice melting are all suspected as factors behind the unusual heating of the ocean. Scientists are investigating further to uncover the full extent of the impact on our planet.

Ocean temperatures have been off the charts since mid-March 2023, with the highest average levels in 40 years of satellite monitoring, and the impact is breaking through in disruptive ways around the world. The sea of Japan is more than 7 degrees Fahrenheit (4 degrees Celsius) warmer than average. The Indian monsoon, closely tied to conditions in the warm Indian Ocean, has been well below its expected strength .

Spain, France, England and the whole Scandinavian Peninsula are also seeing rainfall far below normal, likely connected to an extraordinary marine heat wave in the eastern North Atlantic. Sea surface temperatures there have been 1.8 to 5 F (1 to 3 C) above average from the coast of Africa all the way to Iceland. So, what’s going on? El Niño is partly to blame. This climate phenomenon, now developing in the equatorial Pacific Ocean, is characterized by warm waters in the central and eastern Pacific, which generally weakens the trade winds in the tropics .

This weakening of those winds can affect oceans and land around the world. But there are other forces at work on ocean temperatures. Underlying everything is global warming – the continuing rising trend of sea surface and land temperatures for the past several decades as human activities have increased greenhouse gas concentrations in the atmosphere. The world just came off three straight years of La Niña – El Niño’s opposite, characterized by cooler waters rising in the equatorial Pacific .

La Niña has a cooling effect globally that helps keep global sea surface temperatures in check but can also mask global warming. With that cooling effect turned off, the heat is increasingly evident. Arctic sea ice was also unusually low in May and early June, and it may play a role. Losing ice cover can increase water temperatures, because dark open water absorbs solar radiation that white ice had reflected back into space .

These influences are playing out in various ways around the world. The effects of extraordinary Atlantic heat In early June 2023, I visited the NORCE climate center in Bergen, Norway, for two weeks to meet with other ocean scientists. The warm waters and mild winds across the eastern North Atlantic brought a long stretch of sunny, warm weather in a month when more than 70% of days normally would have been downpours .

The whole agricultural sector of Norway is now bracing for a drought as bad as the one in 2018, when yield was 40% below normal. Our train from Bergen to Oslo had a two-hour delay because the brakes of one car overheated and the 90 F (32 C) temperatures approaching the capital were too high to allow them to cool down. Many scientists have speculated on the causes of the eastern North Atlantic’s unusually high temperatures, and several studies are underway .

Weakened winds caused the Azores high, a semi-permanent high pressure system over the Atlantic that affects Europe’s weather, to be especially weak and brought less dust from the Sahara over the ocean during the spring, which may have increased the amount of solar radiation reaching the water. A decrease in human-produced aerosol emissions in Europe and in the United States ove the past 30 years can have a similar effect .