Scientists puzzled by record-breaking ocean warmth

12 May, 2023

The world’s oceans have been warmer than usual recently. The weather phenomenon El Niño is pointed out as a possible culprit, but the top rating is also part of a larger problem that is expected to set many new heat records.

However, something strange has been happening in recent months beneath the surface of the world’s oceans. At the beginning of March, the surface waters suddenly got warmer, reaching an unusually high temperature.

In April, the average temperature was measured at 21.1 degrees in the surface waters of the world’s oceans. The temperature has not been this high since the US weather agency NOAA began its measurements 40 years ago.

Normally, the global average temperature in the oceans usually reaches its peak in March and drops again in early April. But this time, the surface water temperature remained unusually high for an unusually long time and only recently dropped below 21 degrees – but is still higher than has ever been recorded for this time of year.

The curve looks a bit peculiar, compared to how it usually looks. It usually peaks and then falls off some more. But what it is due to is too early to speculate, says Magnus Hieronymus, research leader for ocean climate at SMHI, to TT.

The annual variation of the average global ocean temperature. Graphics: Johan Hallnäs/TT

Looking for explanation

Scientists worldwide are currently studying the causes behind the recent heat record. Some experts believe that the warming phase caused by El Niño may be responsible and predict that the powerful weather phenomenon could make an appearance in the tropical Pacific in the next few months. Meanwhile, the opposite weather event La Niña, which has had a cooling effect on both the sea and climate in recent years, has retreated.

I am increasingly convinced that we are heading into an El Niño. While it is still too early to confirm, we will likely find out during the year, says ocean climate research leader Magnus Hieronymus.

However, other researchers note that several warm areas, such as those in the North Pacific near Alaska and off the coast of Spain, do not fit the El Niño pattern.

-This is an unusual pattern, and it is an extreme event on a global scale and a powerful signal. I think it will take some effort to understand what it is all about, says climate scientist Gabe Vecchi from Princeton University to the AP news agency.

-It is an extreme event on a global scale and a powerful signal. I think it will take some effort to understand what it is all about.

New records

It is becoming increasingly clear that as long as human emissions of greenhouse gases continue to drive global temperatures upward, new record highs in both ocean and atmospheric temperatures can be expected.

-Human influence is making it hotter and hotter all the time, which makes it easier to break heat records and harder to break cold records. I think we will see many heat records broken during this century, warns Hieronymus.

The oceans are particularly vulnerable to climate change, absorbing over 90% of the extra heat. Consequently, the average ocean temperature has increased noticeably in recent decades, with significant consequences for the planet and its inhabitants.

The ocean expands

Warmer oceans lead to increased risks of marine heat waves, which can cause fish kills and other ecological imbalances. Additionally, as water temperatures increase, ocean levels rise due to thermal expansion, posing a significant threat to coastal communities.

Furthermore, as oceans warm, extreme weather events such as storms, hurricanes, and heavy rains can become more frequent and intense, exacerbating flooding. Additionally, a warmer ocean is less capable of absorbing greenhouse gases that contribute to global warming.

-As we continue to heat up, the situation will only get worse, cautions Hieronymus.

Global warming has several serious consequences for the ocean.

The water takes up more space and the sea level rises, in addition, water is added from melting glaciers. The sea level is estimated to rise by 20–60 centimeters by the year 2100, depending on how much greenhouse gases are released, according to the UN’s climate panel IPCC.

The increase in carbon dioxide content in the air has caused a pH drop in the surface layer of the ocean by 0.1 units.

Some coral reefs have bleached and died, likely due to an increase in sea temperatures of two degrees in the late 1990s. This warming was mainly due to an unusually strong El Niño.

Source: The National Encyclopedia

Text: Sofia Eriksson/TT
Photo: Caleb Jones/AP/TT
Graphics: Johan Hallnäs/TT

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