These are only two of ten tipping points that are hitting the Arctic, as described in a earlier post, while additionally there are further tipping points that do not specifically hinge on what happens in the Arctic, e.g. the ozone layer is very vulnerable.

• The latent heat tipping point

An earlier analysis indicates that the latent heat tipping point gets crossed when ocean temperature anomalies on the Northern Hemisphere get higher than 1°C above the 20th century average. The tipping point did get crossed temporarily on several occasions in recent years, but this year it looks to have been crossed irreversibly.

There still is sea ice present in terms of volume. However, there now is virtually no ice left underneath the surface of the Arctic Ocean to act as a buffer. In other words, the sea ice has virtually lost its capacity to act as a buffer to consume further heat entering the Arctic Ocean.

Once the latent heat tipping point is crossed, further incoming heat will have to get absorbed by the Arctic Ocean, instead of getting consumed by the melting of sea ice, as was previously the case.

As long as there is sea ice in the water, this sea ice will keep absorbing heat as it melts, so the temperature will not rise at the sea surface and remain at zero°C. The amount of energy that is consumed in the process of melting the ice is as much as it takes to heat an equivalent mass of water from zero°C to 80°C.

• Ocean Heat

Meanwhile, global heating continues and more than 90% of global heating is going into oceans.

Arctic sea ice is getting very thin and, at this time of year, it is melting rapidly, due to heat entering the Arctic Ocean from above, from the Atlantic Ocean and the Pacific Ocean, and from rivers that end in the Arctic Ocean.

The combination image shows the difference in sea surface temperatures of the Arctic Ocean, between August 4 and 22 (forecast), 2020, 12 GMT. The important difference between the two images is the shrinking of the pale blue area (where the sea surface temperature is below 0°C) in the Arctic Ocean and the increase in areas with other tints of blue (above 0°C).

AUGUST 27, 2020: ARCTIC ABOVE FREEZING POINT

On August 27, 2020, the mean air temperature in the Arctic (80°N to 90°N) was still above freezing point (0°C or 32°F or 273.15°K), well above the mean temperature for 1958-2002 and also above the year 2012 which had exceptionally high temperatures in September.

As long as the air temperature remains above freezing point, the sea ice will keep melting from above, on top of the melting from below that occurs from below as a result from ocean heat entering the Arctic Ocean from the Atlantic Ocean and the Pacific Ocean.

River water flowing into the Arctic Ocean also contributes to rising temperatures.

Furthermore, there are numerous feedbacks, e.g. when black carbon from forest fires settles on sea ice, this causes albedo changes in a self-reinforcing feedback loop, i.e. as less sunlicht gets reflected back up into the sky, more sunlight will be absorbed by the sea ice, speeding up its decline.

Another feedback of the rising heat is that it can cause stronger storms to bring more moisture into the Arctic.

Sea surface temperatures on the Northern Hemisphere are very high at the moment, as high as 33.8°C on August 26, 2020.

• The methane hydrates tipping point

The rising temperature of the Arctic Ocean threatens to destabilize methane hydrates contained in sediments at the seafloor of the Arctic Ocean.

The methane hydrates tipping point could be crossed soon, as the Arctic Ocean is heating up dramatically, which is in part the result of the latent heat tipping point getting crossed, which makes that the temperature of the Arctic Ocean can rise very rapidly.

The methane hydrates tipping point threatens to get crossed as ocean temperature anomalies on the Northern Hemisphere become higher than 1.35°C above the 20th century average, which threatens to occur early next year.

Because the Arctic Ocean in many places is very shallow, heat can quickly reach sediments at the seafloor, which threatens to destabilize methane hydrates. The water of the Arctic Ocean is particularly shallow over the East Siberian Arctic Shelf (ESAS), making that the water there can warm up very quickly during summer heat peaks with heat reaching the seafloor and penetrating cracks in frozen sediments at the seafloor, which can lead to abrupt destabilization of methane hydrates contained in these sediments.

The loss of subsurface sea ice is only one of ten tipping points hitting the Arctic. As the temperature of the oceans keeps rising, more heat will reach sediments at the seafloor of the Arctic Ocean that contain vast amounts of methane.

Large abrupt methane releases in one spot will quickly deplete the oxygen in shallow waters, making it harder for microbes to break down the methane there, while methane that is rising through waters that are only shallow will also be able to enter the atmosphere very quickly, leaving little time for microbes to break down the methane.

A large abrupt release of methane from hydrates in the Arctic can have more warming impact than all carbon dioxide emitted by burning of fossil fuel in a year. This is the result of the high global warming potential (GWP) of methane following its release.

As this warming is concentrated in the Arctic, it will contribute to further methane releases from hydrates in the Arctic.

The situation is extremely dangerous, given the vast amounts of methane present in sediments in the ESAS and given that there is very little hydroxyl in the air over the Arctic to break down the methane.

Ominously, the MetOp-1 satellite recorded a peak methane level of 2945 parts per billion (ppb), at 586 mb on the afternoon of August 18, 2020.

Two days later, the MetOp-1 satellite recorded a peak methane level of 2778 ppb, at 469 mb on the afternoon of August 20, 2020, while mean methane levels reached 1907 ppb.

That afternoon, on August 20, 2020, the MetOp-1 satellite recorded an even higher methane level, of 1923 ppb, at 293 mb, i.e. higher up in the atmosphere.

From the post 'Methane Hydrates Tipping Point threatens to get crossed', at:
https://arctic-news.blogspot.com/…/methane-hydrates-tipping…