ANTARCTICA (above) / Oct.15, 2017 https://go.nasa.gov/2ylu2r3
Subsea permafrost on East Siberian Arctic Shelf in accelerated decline
Written by Nick Breeze
Published: 24 June 2017
Interview by Nick Breeze with Dr Natalia Shakhova and Dr Igor Semiletov
A new scientific paper published in Nature Communication Journal demonstrates that the mechanisms of destabilisation of subsea permafrost, contrary to previous claims, provide new insights into increased emissions from the worlds largest deposits of methane, that exists in the East Siberian Arctic Shelf (ESAS).
The subsea permafrost has for thousands of years acted as a seal, restricting the flow of gas through the water column to the atmosphere. This paper clearly shows that permafrost degradation and the occurrence of gas migration pathways are key factors in controlling the emissions.
Knowing the rate of emission and mechanism of permafrost degradation is a prerequisite to meaningful predictions of near-future methane releases in the Arctic. In this interview with two of the leading authors of this paper, Dr Natalia Shakhova and Dr Igor Semiletov, we learn that the decay of the subsea permafrost, even that which was submerged relatively recently (less than 1000 years ago) is currently occurring and, due to manmade global warming, there is no known countervailing force to stop the trend of further decay and increased emissions. …
Greenland northeast coast (above) / Oct.17, 2017 https://go.nasa.gov/2zyl47R
Dr. Shakhova: Gas in the areas of hotspots is releasing from the seabed deposits, in which free gas has accumulated for hundreds of thousands, or even for a million years. This is why the amount of this gas and its power in releasing (due to its high pressure) is tremendous.
That would allow large releases of methane and whatever you call it – outburst, bomb, or whatever, I see no point to say no to such a possibility. I’m afraid to say yes because we still have to learn so much about the mechanism.
Dr. Shakhova: The importance of hydrates involvement in methane emissions is overestimated. The hydrate is just one form of possible reservoirs, in which pre-formed methane could be preserved in the seabed if there are proper pressure/temperature conditions; it is just the layer of hydrates composes just few hundred of meters – this is a very small fraction compared to thousands of meters of underlying gas-charged sediments in the ESAS.
Dr. Semiletov added that the 5 billion tonnes of methane that is currently in the Earth’s atmosphere represents about one percent of the frozen methane hydrate store in the East Siberian Arctic Shelf. He finishes emphasising “…but we believe the hydrate pool is only a tiny fraction of the total.” …
Dr. Shakhova: The area of hotspots is determined by the fraction of subsea permafrost that is disintegrated. The process of permafrost degradation started thousands of years ago and it is now a key driver triggering methane emissions from these long-preserved deposits.
Emissions that are occurring right now are the result of a combined effect of natural and anthropogenic warming and they will be accelerated until warming is turned to cooling. Even after it happens, there is no mechanism to stop permafrost disintegration in the ESAS besides shelf exposure above the sea level that would serve to freeze the gas migration paths so that they integrate with the permafrost. Before that, the amount of methane that is releasing will increase while the supply lasts.
As gas within the sedimentary basins of the ESAS have been accumulating for a million years with no way to be released earlier, the supply for currently occurring emissions is tremendous. Because the shelf area is very shallow (mean depth is less than 50 metres), a fraction of these emissions will reach the atmosphere. The problem is that this fraction would be enough to alter the climate on our planet drastically.
Sonar gas flux estimation by bubble insonification: Application to methane bubble flux from seep areas in the outer Laptev Sea
Article · June 2017
Sonar surveys provide an effective mechanism for mapping seabed methane flux emissions, with Arctic submerged permafrost seepage having great potential to significantly affect climate. We created in situ engineered bubble plumes from 40 m depth with fluxes spanning 0.019 to 1.1 L s⁻¹ to derive the in situ calibration curve (Q(σ)). These nonlinear curves related flux (Q) to sonar return (σ) for a multibeam echosounder (MBES) and a single-beam echosounder (SBES) for a range of depths. The analysis demonstrated significant multiple bubble acoustic scattering – precluding the use of a theoretical approach to derive Q(σ) from the product of the bubble σ(r) and the bubble size distribution where r is bubble radius. The bubble plume σ occurrence probability distribution function (Ψ(σ)) with respect to Q found Ψ(σ) for weak σ well described by a power law that likely correlated with small-bubble dispersion and was strongly depth dependent. Ψ(σ) for strong σ was largely depth independent, consistent with bubble plume behavior where large bubbles in a plume remain in a focused core. Ψ(σ) was bimodal for all but the weakest plumes. Q(σ) was applied to sonar observations of natural arctic Laptev Sea seepage after accounting for volumetric change with numerical bubble plume simulations.
Simulations addressed different depths and gases between calibration and seep plumes. Total mass fluxes (Qm) were 5.56, 42.73, and 4.88 mmol s⁻¹ for MBES data with good to reasonable agreement (4–37 %) between the SBES and MBES systems. The seepage flux occurrence probability distribution function (Ψ(Q)) was bimodal, with weak Ψ(Q) in each seep area well described by a power law, suggesting primarily minor bubble plumes. The seepage-mapped spatial patterns suggested subsurface geologic control attributing methane fluxes to the current state of subsea permafrost.
The Laptev Sea & Ostrov Strizheva Island, Russia https://go.nasa.gov/2zzs3NA
The Laptev Sea (Russian: мо́ре Ла́птевых, tr. more Laptevykh; Yakut: Лаптевтар байҕаллара) is a marginal sea of the Arctic Ocean. It is located between the northern coast of Siberia, the Taimyr Peninsula, Severnaya Zemlya and the New Siberian Islands. Its northern boundary passes from the Arctic Cape to a point with co-ordinates of 79°N and 139°E, and ends at the Anisiy Cape. The Kara Sea lies to the west, the East Siberian Sea to the east.
The sea is named after the Russian explorers Dmitry Laptev and Khariton Laptev; formerly, it had been known under various names, the last being Nordenskiöld Sea (Russian: мо́ре Норденшёльда), after explorer Adolf Erik Nordenskiöld. The sea has a severe climate with temperatures below 0 °C (32 °F) over more than 9 months per year, low water salinity, scarcity of flora, fauna and human population, and low depths (mostly less than 50 meters). It is frozen most of the time, though generally clear in August and September.
The sea shores were inhabited for thousands of years by indigenous tribes of Yukaghirs and then Evens and Evenks, which were engaged in fishing, hunting and reindeer husbandry. They were then settled by Yakuts and later by Russians. Russian explorations of the area started in the 17th century. They came from the south via several large rivers which empty into the sea, such as the prominent Lena River, the Khatanga, the Anabar, the Olenyok, the Omoloy and the Yana. The sea contains several dozen islands, many of which contain well-preserved mammoth remains.
Major human activities in the area are mining and navigation on the Northern Sea Route; fishing and hunting are practised but have no commercial significance. The largest settlement and port is Tiksi.
The Laptev Sea Rift is a divergent tectonic plate boundary between the North American Plate and the Eurasian Plate located on the Arctic Ocean coast of northeastern Siberia in Russia. The Laptev Sea Rift is the continuation of the Gakkel Ridge (Mid-Arctic Ridge) into the continental crust of Siberia. It starts offshore in the continental shelf and continues onshore to a point located in the Chersky Range where the boundary motion changes from extension to compression.
Ostrov Strizheva (Ostrov Strizhëva) is a island (class T – Hypsographic) in Respublika Sakha (Yakutiya) (Sakha (Yakutiya)), Russia (Europe) with the region font code of Russia/ Central Asia… Ostrov Strizhëva is also known as Ostrov Strizheva, Ostrov Strizhëva, Остров Стрижёва.
Its coordinates are 75°19’60” N and 135°19’1″ E in DMS (Degrees Minutes Seconds) or 75.3333 and 135.317 (in decimal degrees). Its UTM position is ND06 and its Joint Operation Graphics reference is NS53-02.
ANTARCTICA (above) / Oct.17, 2017 https://go.nasa.gov/2zyRoaA
Novaya Zemlya, Russia (above) / Oct.17, 2017 https://go.nasa.gov/2zyTJm2
Novaya Zemlya Russia
Novaya Zemlya (Russian: Но́вая Земля́; IPA: [ˈnovəjə zʲɪmˈlʲa], lit. new land), also known, especially in Dutch, as Nova Zembla, is an archipelago in the Arctic Ocean in northern Russia and the extreme northeast of Europe, the easternmost point of Europe lying at Cape Flissingsky on the Northern island. Novaya Zemlya is composed of two islands, the northern Severny Island and the southern Yuzhny Island, which are separated by Matochkin Strait. Administratively, it is incorporated as Novaya Zemlya District, one of the twenty-one in Arkhangelsk Oblast, Russia.Municipally, it is incorporated as Novaya Zemlya Urban Okrug.
Novaya Zemlya was a sensitive military area during the Cold War years and it is still used today. The Soviet Air Force maintained a presence at Rogachevo on the southern part of the island, on the westernmost peninsula (71.61787°N 52.47884°E). It was used primarily for interceptor aircraft operations but also provided logistical support for the nearby nuclear test area.
Novaya Zemlya was the site of one of the two major nuclear test sites managed by the USSR, used for air drops and underground testing the largest of the Soviet nuclear bombs, in particular the October 30, 1961 air burst explosion of Tsar Bomba, the largest, most powerful nuclear weapon ever detonated.
The Davis Strait, Labrador Sea & Greenland west coast (above) / Oct16, 2017 https://go.nasa.gov/2zz0Qe4
ARCTIC: Baffin Bay west coast of Greenland (above) / Oct.16, 2017 https://go.nasa.gov/2ynflnA
ARCTIC (above) / Oct.16, 2017 https://go.nasa.gov/2ztLtDG
Hudson Bay far northern Canada (above) / Oct.16, 2017 https://go.nasa.gov/2ypbtlQ
ANTARCTICA (above) / Oct.15, 2017 https://go.nasa.gov/2zqaS10
ANTARCTICA (above) / Oct.13, 2017 https://go.nasa.gov/2yj1AWO
ANTARCTICA: detail Amery Ice Shelf (above) / Oct.10, 2017 https://go.nasa.gov/2zev31N