High temperatures despite La Niña?

2 months ago 33

[ Northern Hemisphere SSTA - click on images to enlarge ]

Temperatures remain extremely high, even though La Niña conditions may already be present, as illustrated by the above image, showing sea surface temperature anomalies (SSTA) versus 1981-2011.

The image on the right shows Northern Hemisphere (45.00°,90.00°) SSTA on September 20, 2024. There are only very few cold spots, while massive amounts of ocean heat are present in the North Atlantic and the North Pacific.

SSTA are extremely high in the North Atlantic, reaching a record high for the time of year on September 22, 2024, as illustrated by the image below (SSTA vs 1882-2011).

The image below, by Brian McNoldy shows that ocean heat content in the Gulf of Mexico was at a record high on September 22, 2024.

The danger of methane hydrates getting destabilized

The Gulf Stream keeps pushing Ocean heat toward the Arctic Ocean, and this can be accelerated by storms that are amplified due to high sea surface temperatures, deformation of the Jet Stream and a freshwater lid forming at the surface of the North Atlantic.

At the same time, Arctic sea ice starts expanding rapidly in extent at this time of year, effectively sealing off the Arctic Ocean and making it hard for heat to get transferred from the surface of the Arctic Ocean to the atmosphere.

As discussed in earlier posts, Arctic sea ice has become very thin, diminishing its capacity to act as a buffer that consumes ocean heat entering the Arctic Ocean from the North Atlantic. Sea ice constitutes a latent heat buffer, consuming incoming heat as it melts. While the ice is melting, all energy (at 334 J/g) goes into changing ice into water and the temperature remains the same. Once all ice has turned into water, all subsequent energy goes into heating up the water, and will do so at 4.18 J/g for every 1°C the temperature of the water rises.

[ The Latent Heat Buffer ]

Ocean heat that was previously consumed by melting the sea ice, can no longer get consumed by melting of the sea ice once Arctic sea ice has become very thin, and further incoming heat instead gets absorbed by the Arctic Ocean, rapidly pushing up the temperature of the water of the Arctic Ocean.

The danger is that, as the water of the Arctic Ocean keeps heating up, more heat will reach the seafloor and destabilize methane hydrates contained in sediments at the seafloor, resulting in eruptions of huge amounts of methane.

The image below illustrates how incoming ocean heat that previously was consumed in the process of melting of the sea ice, is now causing the water of the Arctic Ocean to heat up, with more heat reaching the seafloor of the Arctic Ocean, which has seas that in many places are very shallow.

[ Latent heat loss, feedback #14 on the Feedbacks page ]

Eruptions from hydrates occur at great force, since the methane expands 160 times in volume when it vapoizes, resulting in the methane rapidly rising in the form of plumes, leaving little or no opportunity for microbes to decompose the methane in the water column, which especially applies to the many areas where the Arctic Ocean is very shallow. Furthermore, the atmosphere over the Arctic contains very little hydroxyl, resulting in methane persisting in the air over the Arctic much longer than elsewhere.

Climate Emergency Declaration

The situation is dire and the precautionary principle calls for rapid, comprehensive and effective action to reduce the damage and to improve the situation, as described in this 2022 post, where needed in combination with a Climate Emergency Declaration, as discussed at this group.