Sunday, 13 October 2019

Report on the Arctic from Nicholas Humphrey

The Arctic Is In The Driver's 


13 September, 2019

The Arctic - a distant and mysterious place to most of the population on this planet - is increasingly controlling our destiny and future as a species, not to mention other species with regards to abrupt climate change and the 6th mass extinction. Humanity's extreme and accelerated burning of fossil fuels has altered the atmosphere in a cosmic blink of an eye, bringing about changes with a speed unprecedented in the past 66 million years. 
This fossil fuel "carbon bomb" is tied to the rapid economic growth of industrialization, fed by an abundant energy source, resulting in humanity's explosion in population and consumption.  The waste products of our fossil fuel burning have served as the ignition sequence for a new "carbon bomb" of permafrost melt, the decomposition of hundreds of thousands of years of accumulated organic material, as part of the destruction of the global cryosphere. 
1. The Arctic as a whole is already in the range of +3-4 C/5.5-7 F above pre-industrial times. The Arctic is now a permanently altered climate region. It will continue to warm rapidly given the existing greenhouse gas concentration in Earth's atmosphere. 
On a global scale, the current carbon dioxide equivalent concentration (based on the heating impact of all greenhouse gases) is near 500 parts per million (NOAA). In the past decade, the carbon dioxide equivalent concentration has risen, on average, near 3.5 ppm/yr. A (conservative) long-term warming expectation based on such a concentration would be over +2.5 C/4.5 F for the land air+sea surface. This would likely translate to +7-8 C/12.5-14.5 F of warming in the Arctic, supporting the rapid destruction of Arctic sea ice and permafrost discussed below.  
The rise in carbon dioxide and carbon dioxide equivalent since 1700 (NOAA). Note the "great acceleration" after 1950.

Average annual temperature anomalies in 2014-2018 relative to the 1880-1909 baseline.

2. Sea ice is collapsing. The current  *linear* trend (based on 1979-2019) shows September monthly averaged sea ice volume will fall below 1,000 cubic km by 2030. That's on average over the whole month. Such a low volume on a daily or weekly basis would be expected to happen years before. September sea ice volume was the 2nd lowest on record in 2019 (4,188 cubic km; the record is 3,787 cubic km in 2012).
Sea ice extent collapse in the 2nd half of the 20th century.
The loss of sea ice extent and volume - which serves both as a reflective feature to reduce heating and as a controller of the heat already in the climate system via melting and refreezing (latent heat) - will mean continued amplification of regional and ultimately global warming. It will also mean increasing extremes caused by jet stream waves which amplify and stall out for weeks at a time. These increasingly common standing waves/blocking patterns - caused by a reduction in the temperature difference between the Arctic and mid-latitudes - can drive destructive extreme weather events. Check out this recent presentation by Dr. Jennifer Francis of Rutgers University on the Arctic amplification-jet stream connection. 

3. Permafrost - both land-based and sub-sea permafrost under the shallow areas of the Arctic Ocean - is melting much faster than projected originally. Terrestrial permafrost is melting across the Northern Hemisphere abruptly by way of landslides, thaw lakes and coastal erosion as sea ice is lost. The terrestrial permafrost contains 1,450-1,600 billion tonnes of organic carbon (per the Intergovernmental Panel on Climate Change Cryosphere Report) and hundreds of billions of tonnes of it will be released assuming a high emissions scenario (the scenario we are currently on). For comparison, about 275 billion tonnes of carbon have been released to the atmosphere since 1750 in the form of carbon dioxide (1 ppm of additional carbon dioxide = 2.13 billion tonnes of carbon; The actual carbon dioxide concentration has risen 130 ppm from near 280 ppm in 1750 to 410 ppm in 2019). 
Much of these terrestrial permafrost emissions will be as carbon dioxide, but a portion of it will be methane (CH4), a powerful greenhouse gas on short-time scales (96 times more powerful than CO2 on a 20-yr timescale). There is also evidence that a significant amount of nitrous oxide, another powerful and long-lived greenhouse gas is already being released. These emissions will accelerate as rapidly as the permafrost holding the organic material melts.
Sub-sea permafrost in the East Siberian Arctic Shelf (under the East Siberian and Laptev Seas) is methane-bearing via methane hydrates and free pressurized gases. It is estimated that >1,400 billion tonnes of methane are stored in the ESAS, with its ability to be released into the free atmosphere by the fact that the sea is so shallow over the continental shelf. 
"Maps of the Arctic Ocean (AO) highlighting specific features of the East Siberian Arctic Shelf (ESAS): (a) Predicted areas of hydrate deposits over the AO, including the shallow ESAS, shown in blue; (b) bathymetry of the AO; red color refers to depth <50 m. As seen from the panels, the ESAS represents a major fraction of the AO shallow continental shelf." (From Shakhova, Semilitov & Chuvilin, 2019).
As the Arctic Ocean warms and sea ice is retreating from the peripheral seas for months at a time, methane emissions are increasing dramatically. With the sub-sea permafrost melting, the risk for abrupt releases of tens of billions of tonnes of methane is increasing as emissions pathways grow. High magnitude releases of methane would mean accelerated climate change on timescales of a decade or less.
Ice-free Siberian Arctic waters on October 11, 2019.

4. Greenland, as well as Antarctica, are accelerating in their ice mass loss. This is a major driver of sea level rise. 
Ice mass losses from Greenland and Antarctica; also sea level rise since the late-19th century. Sea level rise has been driven by ice mass loss from the ice sheet, land glaciers, as well as thermal expansion of the oceans.
The middle to worse-case scenarios for sea level rise by the National Ocean and Atmospheric Administration projects up to half a meter of sea level rise (2 feet; relative to the 1990s) by 2050, with 2.5 meters (8 feet) by 2100.

The Intergovernmental Panel on Climate Change, although more conservative in their sea level rise assessments (relative to more recent research), has stated that many coastal locations globally will see once a century extreme sea level events, at least once per year by 2050. The creeping rise of the sea will also enhance the damaging impacts of storm surge from tropical cyclones and other ocean storms. The rate of sea level rise is largely controlled by how rapidly Greenland and (particularly) Antarctica melt. Research by Hansen et al (2016) suggests Greenland and Antarctica melting may cause exponential multi-meter sea level rise during the 21st century. 
Exponential sea level rise as hypothesized by Hansen et al. (2016).
The changes occurring in the Arctic are truly shocking and profound. They will have global impacts on our climate. 1) The high carbon dioxide equivalent concentration will continue to drive climate change for decades even if emissions stop today. 2) The progressive loss of sea ice extent and volume will mean further amplification of regional warming, overall global warming and disrupting the polar jet stream, contributing to extreme weather events such as heat, drought and heavy precipitation. 3) The loss of permafrost - terrestrial and subsea - will mean increasing emissions of carbon dioxide and methane with parts of the Arctic becoming a net carbon emitter. This will accelerate global warming as warming forces more permafrost melt. 4) Further warming caused by humans and increasing Arctic sources will speed up ice sheet mass loss, leading to further sea level rise and extreme sea level events. Obviously, faster global warming is a threat to global agricultural production (extreme heat, multi-year droughts, very heavy precipitation/floods), infrastructure and human habitation (severe storms/sea level rise/permafrost melt), and a biosphere already in the early stages of a mass extinction event.
---Meteorologist Nick Humphrey

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