Heat waves in the Arctic Ocean | Polarjournal
Most areas of the world’s oceans, especially the polar oceans, were up to 5°C warmer on July 22 than the average between 1991 – 2020, NOAA’s map shows (Graphic: NOAA)

Many countries in Europe, parts of the USA and Canada, and also large parts of Russia are currently experiencing massive heat waves. Anyone thinking that a dip in the sea will cool things down will be disappointed, because the oceans are also affected by an unprecedented rise in temperature. Since May/June, this has been extending all the way to the Arctic Ocean.

Looking at NOAA’s most recent overview map of sea surface temperature anomalies from the long-term mean, large parts of the edges of the Arctic Ocean light up in colors ranging from yellow to dark red. Most affected are the western end of the Northwest Passage, parts of the Laptev and Kara Seas, and northwestern Svalbard, where a +5°C deviation from the long-term average 1991 – 2020 has been measured in each case. There are only two areas with lower temperatures than normal: the Disko Bay in Greenland and the north-eastern part of Iceland. In the Southern Ocean, most areas are also warmer than before, although not to the same extent as in the north. Overall, however, experts have been very concerned about this trend for months.

There is nothing new per se about the fact that the oceans are getting increasingly warmer. But what the satellites and measuring stations had reported over the past weeks startles expert groups all over the world: There is hardly a region without continuously reporting above-average water temperatures since May, much too early according to the European Space Agency: “The average temperatures observed last month are rather typical for late summer. Prior to June 2023, such temperatures have been observed in the ERA5 dataset since 1979, at the earliest toward the end of July.”

Also in the Arctic, extreme water temperatures were measured that the National Oceanic and Atmospheric Administration NOAA had declared the highest level in “Heat Wave Watch” (Category 5 = “Beyond Extreme”). Ever since, these extreme events have been repeated on an almost daily basis, with no end in sight.

The Southern Ocean has also been showing above-average water temperatures since last year, according to the World Meteorlogical Organization WMO. In particular, the west coast of the Antarctic Peninsula, the Weddell Sea sector, and the east coast in the Australian sector have been about 2°C warmer since July 2022, while parts of the Pacific sector have been cooler.

Summer, sun, Svalbard. Those who visited Svalbard in June enjoyed vastly warm conditions. Long lasting strong high pressure systems, created by a shifting jet stream, supported the continued warming of the water masses. Image: Mirjana Binggeli

Experts cite the lack of winds over the oceans, which prevent the mixing of water masses and intensify warming, as a direct cause of the above-average warming. At the same time, the Sahara dust in the atmosphere, which normally scatters solar radiation and reflects parts of the radiation, is missing. In addition, the jet stream has shifted, creating large areas of high pressure that have also accelerated warming.

However, in the long term, expert groups blame global warming and the multi-decade fluctuations in the North Atlantic circulation and associated heat transport. These stronger varying fluctuations are also caused by global warming and their own natural fluctuations.

The Arctic sea ice season has not been as bad as in previous years. But higher temperatures have now caused sea ice to melt rapidly in northwest and north Svalbard and along the Greenland coast. (Symbol image: Mirjana Binggeli)

The effects of the heat wave in large parts of the Arctic and Southern Oceans are, on the one hand, extreme weather events such as increased hurricane activity, extreme rainfall and thunderstorms in Europe with simultaneous heat waves. Widespread brush and forest fires are also linked to ocean events.

On the other hand, faster sea ice melts, or the non-formation of sea ice in parts of Antarctica, are due to the higher temperatures. In fact, this year’s Arctic season was somewhat better than previous years in terms of sea ice. But in recent weeks, the sea ice has now been melting quite rapidly in northern Svalbard as well, and even large parts of the East Greenland coast are now breaking up rapidly. On the other hand, on the coasts of Alaska and in western Nunavut, the ice has completely disappeared. Also in the Chukchi Sea, parts of the Laptev Sea and in the Kara Sea the search for sea ice is in vain.

Antarctica, on the other hand, is heading for a new negative record, already lacking more than 2.5 million square kilometers of ice on average, and the current extent is 1.6 million square kilometers lower than the last negative record in 2022. What impact this lack of sea ice will have on Antarctic ecosystems and inhabitants is difficult to assess at this time.

Dr Michael Wenger, PolarJournal

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