Saturday, May 22, 2021

Arctic Ocean invaded by hot, salty water


Sea surface temperatures on the Northern Hemisphere have been rising dramatically over the years, as illustrated by above image, indicating that the latent heat tipping point is getting crossed, while the methane hydrates tipping point could get crossed soon, depending on developments.

At the moment, the surface temperature of most of the Arctic ocean's is still below 0°C.

Heat is entering the Arctic Ocean from the south, as illustrated by the image on the right. Hot, salty water is entering the Arctic Ocean from the Atlantic Ocean as currents dive underneath the ice, causing the ice to melt from below. 
[ click on images to enlarge ]

The image on the right, from the NSIDC article A step in our Spring, compares sea ice age between March 12 to 18 for the years 1985 (a) and 2021 (b).

The bottom graph (c) shows a time series from 1985 to 2021 of percent ice coverage of the Arctic Ocean domain. The Arctic Ocean domain is depicted in the inset map with purple shading.

At the end of the ice growth season in mid-March, 73.3% of the Arctic Ocean domain was covered by first-year ice, while 3.5% was covered by ice 4+ years old. 

This compares to 70.6% and 4.4% respectively in March 2020.

In March 1985, near the beginning of the ice age record, the Arctic Ocean region was comprised of nearly equal amounts of first-year ice (39.3%) and 4+ year-old ice (30.6%).

Sea ice that hasn't yet survived a summer melt season is referred to as first-year ice. This thin, new ice is vulnerable to melt and disintegration in stormy conditions. Ice that survives a summer melt season can grow thicker and less salty, since snow that thickens the ice contains little salt. Thickness and salt content determine the resistance of the ice to melt. Multiyear ice is more likely to survive temperatures that would melt first-year ice, and to survive waves and winds that would break up first-year ice.

The image on the right shows a forecast of the thickness of the sea ice, run on May 20, 2021 and valid for May 21, 2021. 

An area is visible north of Severnaya Zemlya toward the North Pole where thickness is getting very thin, while there is one spot where the ice has virtually disappeared. 

The spot is likely a melting iceberg, the animation on the right shows that the spot has been there for quite a few days, while the freshwater in this spot appears to result from melting amid salty water. 

Overall, sea ice is getting very thin, indicating that the buffer constituted by the sea ice underneath the surface is almost gone, meaning that further heat entering the Arctic Ocean will strongly heat up the water. 

As the animation underneath on the right shows, freshwater is entering the Arctic Ocean due to runoff from land, i.e. rainwater from rivers, meltwater from glaciers and groundwater runoff from thawing permafrost. 

At the same time, very salty water is entering the Arctic Ocean from the Atlantic Ocean. 

The map below shows how salty and hot water from the Atlantic Ocean enters the Arctic Ocean along two currents, flowing on each side of Svalbard, and meeting at this area north of Severnaya Zemlya where thickness is getting very low. 

The blue color on the map indicates depth (see scale underneath). 

The image below, by Malcolm Light and based on Max & Lowrie (1993), from a recent post, shows vulnerable Arctic Ocean slope and deep water methane hydrates zones below 300 m depth. 

Malcolm Light indicates three areas: 
Area 1. Methane hydrates on the slope;
Area 2. Methane hydrates on the abyssal plane; 
Area 3. Methane hydrates associated with the spreading Gakkel Ridge hydro-thermal activity (the Gakkel Riidge runs in between the northern tip of Greenland and the Laptev Sea). 


The freezing point of freshwater is 0°C or 32°F. For salty water, the freezing point is -2°C or 28.4°F.

During April 2021, sea ice was about 160 cm thick.

In June and July 2021, thickness will fall rapidly, as illustrated by the image on the right by Nico Sun. 

Sea ice acts as a buffer, by consuming energy in the process of melting, thus avoiding that this energy causes a temperature rise of the water. 

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.

The accumulated ice melt energy until now is the highest on record, as illustrated by the image on the right, by Nico Sun.

The image below further illustrate the danger. As the temperature of the water keeps rising, more heat will reach sediments at the seafloor of the Arctic Ocean that contain vast amounts of methane, as discussed at this page and in this post.

Ominously, methane levels reached a peak of 2901 ppb at 469 mb on May 13, 2021. 

Research

In the extract of a 2008 paper, Natalia Shakhova et al. conclude: ". . we consider release of up to 50 Gt of predicted amount of hydrate storage as highly possible for abrupt release at any time."


The video below contains excerpts from Nick Breeze's interview with Natalia Shakhova at the European Geophysical Union in Vienna, 2012, on the likelihood and timeframe of a large methane release from the seafloor of the Arctic Ocean. 

Natalia Shakhova: "The total amount of methane in the atmosphere is about 5Gt. The amount of carbon in the form of methane in this Arctic shelf is - approximately - from hundreds to thousands Gt and, of course, only 1% of [such an] amount is required to double the atmospheric burden of methane."

"But to destabilize 1% of this carbon pool, I think, not much effort is needed, considering the state of the permafrost and the amount of methane involved, because what divides the methane from the atmosphere is a very shallow water column and the weakening permafrost, which is losing its ability to seal, to serve as a seal, and this is, I think, not a matter of thousands of years, it's a matter of decades, at most hundred years." 

(Natalia talks with Igor Semiletov)
Natalia Shakhova: "Just because this area is seismically and tectonically active, and there was some investigation that the tectonic activity was increasing, and the seismic activity, the destabiliation of the ground, just mechanical forcing destabiliation [may suffice to act as] additional pathway for this methane to escape. There are many factors that are very convincing for us [to conclude] that it might happen."

Elaborating on the timeframe.
Natalia Shakhova: "Not any time, any time sounds like it might happen today, it might happen tomorrow, the day after tomorrow . . " 
Igor Simelitov: "It might!"


The image below was created with content from a 2019 paper by Natalia Shakhova et al. It concludes that methane releases could potentially increase by 3-5 orders of magnitude, considering the sheer amount of methane preserved within the shallow East Siberian Arctic Shelf seabed deposits and the documented thawing rates of subsea permafrost reported recently.

In a 2021 paper by researchers from Europe, Russia and the U.S., results from field research are published showing that methane is getting released from locations deep below the submarine permafrost. Lead author, Julia Steinbach, from Stockholm University, says: “The permafrost is a closed lid over the seafloor that’s keeping everything in place. And now we have holes in this lid.” 

In the video below, Nick Breeze interviews Igor Semiletov on methane plumes detected during this 2020 field research over the East Siberian Arctic Shelf (ESAS).


In the video below, Nick Breeze interviews Örjan Gustafsson on field research on methane in the East Siberian Arctic Shelf (ESAS)


In the video below, Peter Wadhams analyses the threat of Arctic methane releases.


In the video below, Guy McPherson discusses the situation.


In conclusion, temperatures could rise dramatically soon. A 3°C will likely suffice for humans to go extinct, making it in many respects rather futile to speculate about what will happen in the longer term. On the other hand, the right thing to do is to help avoid the worst things from happening, through comprehensive and effective action as described in the Climate Plan.

Links

• NOAA Climate at a Glance

• Danish Meteorological Institute - Arctic temperature
http://ocean.dmi.dk/arctic/meant80n.uk.php

• Freezing point of water - Climate Change: Arctic sea ice

• Arctic surface temperature

• NSIDC: A step in our Spring, image credit: T. Tschudi, University of Colorado, and W. Meier and J.S. Stewart, National Snow and Ice Data Center/Image by W. Meier

• Arctic sea ice - thickness and salinity - navy.mil
https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/arctic.html

• CryosphereComputing - by Nico Sun
https://cryospherecomputing.tk

• A 4.5 km resolution Arctic Ocean simulation with the global multi-resolution model FESOM 1.4 - by Qiang Wang et al. 

• Max, M.D. & Lowrie, A. 1993. Natural gas hydrates: Arctic and Nordic Sea potential. In: Vorren, T.O., Bergsager, E., Dahl-Stamnes, A., Holter, E., Johansen, B., Lie, E. & Lund, T.B. Arctic Geology and Petroleum Potential, Proceedings of the Norwegian Petroleum Society Conference, 15-17 August 1990, Tromso, Norway. Norwegian Petroleum Society (NPF), Special Publication 2 Elsevier, Amsterdam, 27-53.
https://www.elsevier.com/books/arctic-geology-and-petroleum-potential/vorren/978-0-444-88943-0

• Extinction by 2027- by Malcolm Light
https://arctic-news.blogspot.com/2021/05/extinction-by-2027.html


• Anomalies of methane in the atmosphere over the East Siberian shelf: Is there any sign of methane leakage from shallow shelf hydrates? - by Shakhova, Semiletov, Salyuk and Kosmach (2008)
https://www.cosis.net/abstracts/EGU2008/01526/EGU2008-A-01526.pdf

• Understanding the Permafrost–Hydrate System and Associated Methane Releases in the East Siberian Arctic Shelf - by Natalia Shakhova, Igor Semiletov and Evgeny Chuvilin 
https://www.mdpi.com/2076-3263/9/6/251

• A Massive Methane Reservoir Is Lurking Beneath the Sea 


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