Earthquakes in the Arctic Ocean

Earthquakes in the Arctic Ocean

indications of imminent catastrophic methane eruptions?

1. Methane over Greenland

The image below shows high methane concentrations over Greenland and over the Arctic Ocean.

[ Yellow areas indicate methane readings of 1950 ppb and higher - click on image to enlarge ]

The large yellow areas on this image indicate that the methane entered the atmosphere there. This is especially likely when such large yellow areas keep appearing in the same area over a few days. In the case of the large yellow areas around Novaya Zemlya, the methane is likely to have travelled there underneath the sea ice, from the Gakkel Ridge, to enter the atmosphere where the sea ice was thin or fractured enough for the methane to pass through, as discussed in earlier posts.

As described in the post High methane readings over Greenland, huge temperature swings can hit areas over Greenland over the course of a few days. Temperature anomalies may go down as low as as -20°C one day, then climb as high as 20°C a few days later, to hit temperature anomalies as low as -20°C again some days later.

This could explain the methane over Greenland. Methane is present in the Greenland ice sheet in the form of hydrates and free gas. These huge temperature swings are causing the ice to expand and contract, thus causing difference in pressure as well as temperature. The combined shock of wild pressure and temperature swings is causing movement and fractures in the ice, and this enables methane to rise to the surface and enter the atmosphere.

To further illustrate this, the image below shows recent temperature anomaly forecasts over Greenland.

[ click on image to enlarge ]

2. What is causing these extreme weather events?

Frigid cold weather in the U.S., torrential rain and flooding in the U.K., and wild temperature swings over Greenland. What is causing these extreme weather events? 

As discussed in many previous posts, the Arctic has become warmer than it used to be and temperatures in the Arctic are rising several times faster than global temperatures. This decreases the temperature difference between the areas to the north and to the south of the Jet Stream, which in turn decreases the speed at which the Jet Stream circumnavigates the globe, making the Jet Stream more wavier and increasing opportunities for cold air to descend from the Arctic and for warm air to enter the Arctic.

3. Did temperature swings also trigger earthquakes?

[ click on image to enlarge ]

These wild temperature swings may be causing even further damage, on top of the methane eruptions from the heights of Greenland. Look at the above map, showing earthquakes that hit the Arctic in March 2014.

Topographic map of Greenland
without the Greenland Ice Sheet.

BTW, above map doesn't show all earthquakes that occurred in the Arctic Ocean in March 2014. An earthquake with a magnitude of 4.5 on the Richter scale hit the Gakkel Ridge on March 6, 2014.

Importantly, above map shows a number of earthquakes that occurred far away from faultlines, including a M4.6 earthquake that hit Baffin Bay and a M4.5 earthquake that hit the Labrador Sea. These earthquakes are unlikely to have resulted from movement in tectonic plates. Instead, temperature swings over Greenland may have triggered these events, by causing a succession of compression and expansion swings of the Greenland ice mass, which in turn caused pressure changes that were felt in the crust surrounding the Greenland Ice Sheet.

Glaciers could be the key to make this happen. Glaciers typically move smoothly and gradually. It could be, however, that such wide temperature swings are causing glaciers to come to a halt, temporarily, causing pressure to build up over a day or so, to then suddenly start moving again with a shock. Intense cold can literally freeze a glacier in its track, to be shocked into moving again as temperatures rise abruptly by 40°C or so. This can send shockwaves through the ice sheet into the crust and trigger earthquakes in areas prone to destabilization. The same mechanism could explain the high methane concentrations over the heights of Greenland and Antarctica.

Ominously, patterns of earthquakes can be indicators of bigger earthquakes yet to come.

4. Situation looks set to get a lot worse

This situation looks set to get a lot worse. Extreme weather events and wild temperature swings look set to become more likely to occur and hit Greenland with ever greater ferocity. Earthquakes could reverberate around the Arctic Ocean and destabilize methane held in the form of free gas and hydrates in sediments underneath the Arctic Ocean.

Meanwhile, as pollution clouds from North America move (due to the Coriolis Effect) over the Atlantic Ocean, the Gulf Stream continues to warm up and carry warmer water into the Arctic Ocean, further increasing the likelihood of methane eruptions from the Arctic seafloor.

The above image shows the Gulf Stream off the coast of North America, while the image below shows how the Gulf Stream continues, carrying warmer water through the Atlantic Ocean into the Arctic Ocean.

Feedbacks, such as the demise of the Arctic's snow and ice cover, further contribute to speed up the unfolding catastrophe. Methane eruptions from the seafloor of the Arctic Ocean have become especially noticeable over the past half year. The big danger is that this will develop into runaway global warming, as discussed in the recent post Feedbacks in the Arctic.

Furthermore, as-yet-unknown feedbacks may start to kick in. As an example, submarine earthquakes and volcanoes could add nutrients into the water that feed methane-producing (methanogenic) microbes. A recent study found that expansion of such microbes could have played a large role in the end-Permian extinction, and that it was catalyzed by increased availability of nickel associated with volcanism. Authors support their hypothesis with an analysis of carbon isotopic changes leading up to the extinction, phylogenetic analysis of methanogenic archaea, and measurements of nickel concentrations in South China sediments.

5. Need for comprehensive and effective action

The situation is dire and calls for comprehensive and effective action as described at the Climate Plan.




Related

- Methane Release caused by Earthquakes
http://arctic-news.blogspot.com/2013/09/methane-release-caused-by-earthquakes.html

- Seismic activity
http://arctic-news.blogspot.com/p/seismic-activity.html

- Climate Plan
https://arctic-news.blogspot.com/p/climateplan.html

High methane readings over Greenland

High methane readings have been recorded over Greenland since the start of February 2014. The image below shows methane readings of 1950 ppb and higher in yellow on February 9, 2014.

The animation below shows that high methane readings (1950+ ppb in yellow) have been showing up over Greenland since the start of February 2014.

[ Note: this animation is a 3.28 MB file that may take some time to fully load ]

What could have caused these high methane readings? The persistence with which the methane shows up over Greenland indicates that it did indeed originate from Greenland.

The above animation also illustrates that high methane readings show up every other image. The IASI readings come from a satellite that is orbiting the poles twice daily, with a 12-hour interval, so the satellite passes the North Pole twice every day. This makes that the images follow a day-versus night pattern, indicating that the high methane readings follow a circadian rhythm, suggesting a pattern that is in line with temperature differences between day and night.

There often is a difference in methane readings between day and night, but rarely is it as distinct as is currently the case over Greenland. And indeed, more is currently happening to temperatures over Greenland than mere differences in temperature between day and night.

As discussed in earlier posts such as this one, the once-common temperature difference between the Arctic and lower latitudes has been shattered, and this is weakening the Jet Stream and the Polar Vortex, in turn making it easier for cold air to flow down to lower latitudes and for warmer air to enter the Arctic. As a result, temperatures over Greenland can go from one extreme to another and back, as illustrated by the image with selected cci-reanalyzer.org forecasts below.

[ click on image to enlarge ]

Above image shows that, in some areas over Greenland, temperature anomalies may go down as low as as minus 20 degrees Celsius one day, then climb as high as 20 degrees Celsius a few days laters, to hit temperature anomalies as low as minus 20 degrees Celsius again some days later. These are swings of 40 degrees Celsius that can hit an area over the course of a few days. 

This could explain the methane over Greenland. Methane is present in the Greenland ice sheet in the form of hydrates and free gas. These huge temperature swings are causing the ice to expand and contract, thus causing difference in pressure as well as temperature. The combined shock of wide pressure and temperature differences is causing movement and fractures in the ice allowing methane to rise to the surface and enter the atmosphere.

The image below puts things in perspective, comparing methane over Greenland with methane over the Arctic Ocean.

Above image shows that the amounts of methane over Greenland are huge, while methane is still being released from the seafloor of the Arctic Ocean, in particular along the faultline that runs from the north of Greenland to the Laptev Sea. 

Few people seem to have anticipated these methane releases from the mountains of Greenland. Even worse, similar processes could be going at times on Antarctica, the Himalayas and the Qinghai-Tibet Plateau. I warned about this danger, e.g. in the May 2013 post Is Global Warming breaking up the Integrity of the Permafrost?. The danger that methane will be released in large (and growing) quantities from hydrates and free gas contained in the ice over mountains appears to have been ignored by the IPCC, which puts more weight on my estimate that methane release from hydrates currently amounts to 99 Tg annually, vastly more than the most recent IPCC estimates of 6 Tg per year. 

Without action on climate change, these methane releases threaten to rise even further and cause runaway global warming. This calls for comprehensive and effective action as discussed at the Climate Plan blog. 

Heatwave to hit Greenland

A heatwave with temperature anomalies exceeding 36°F (20°C) is expected to hit Greenland between August 16 and 22, 2014, as illustrated by the image on the left and the animation on the right. 

Such heatwaves can be expected to hit the Arctic more frequently and with greater intensity, as temperatures in the Arctic are rising faster than elsewhere on Earth.

Such heatwaves can result in massive melting on Greenland, as persistent heat changes the texture of the snow and ice cover, in turn reducing its reflectivity. This makes that less sunlight is reflected back into space and is instead absorbed. 

The image below illustrates what a difference the presence of sea ice can make.

from: Arctic Warming due to Snow and Ice Demise

As the NSIDC/NOAA graphs below shows, melting on Greenland has been relatively modest this year when compared to the situation in 2012. By July 12, 2012, 97% of the ice sheet surface had thawed, according to this NASA analysis and this NOAA Arctic Report Card.

Melting on Greenland directly affects sea level rise, and melting on Greenland is accelerating due to a number of factors.

Projections of melting on Greenland have long been based on a warming atmosphere only, ignoring the warmer waters that lubricate glaciers and that warm Greenland's bedrock canyons that sit well below sea level.

Furthermore, there are growing quantities of black carbon deposits as a result of burning of fossil fuel and biomass. High temperatures have recently caused ferocious wildfires in Canada that have in turn caused a lot of black carbon to go up high into the atmosphere.

And of course, the atmosphere over the Arctic is warming up much faster than most models had projected. This in turn causes triggers further feebacks, including more extreme weather events such as heatwaves and rain storms that can be expected to hit Greenland with ever more frequency and ferocity. Further feedbacks include methane eruptions from the heights of Greenland, as discussed at the Arctic Feedbacks Page.

When also taking into account the accelerating impact of such factors on melting in Greenland, sea levels could rise much faster than anticipated, as illustrated by the image below.

from: more than 2.5m sea level rise by 2040? 

Note that sea level rise is only one of the many dangers of global warming, as discussed in the 2007 post Ten Dangers of Global Warming.

The image on the right shows a temperature forecast for August 16, 2014, with parts of Greenland changing in color from blue into green, i.e. above the melting point for snow and ice.

Such high temperatures are now hitting locations close to the North Pole ever more frequently, due to the many feedbacks that are accelerating warming in the Arctic, as discussed at this Feedbacks page.

One of the most dangerous feedbacks is a sudden eruption of huge quantities of methane from the seafloor of the Arctic Ocean, as discussed in a recent post.

The impact of such feedbacks can be accumulative and interactive, resulting in self-reinforcing feedbacks loops that can escalate into runaway warming.

Below is another forecast by ClimateReanalyzer for August 16, 2014, showing the remarkable ‘greening’ of Greenland, as well as the very high temperatures reaching the higher latitudes of North America.

Also see the very high sea surface temperatures around Greenland on the image below, created with ClimateReanalyzer.

Sea surface temperature anomalies on August 15, 2014. 

In conclusion, the situation is dire and calls for comprehensive and effective action, as discussed at the Climate Plan blog. 

Post by Sam Carana.

Huge patches of warm air over the Arctic

Over the past month or so, huge patches with temperature anomalies of over 20 degrees Celsius have been forming over the Arctic.

The three images below show such patches stretch out from Svalbard to Novaya Zemlya (top), north of Eastern Siberia (middle) and over West Greenland and Baffin Bay (bottom).

How these patches with warm air developed is further illustrated by the animation below, which goes from February 12, 2013, to March 18, 2013.

Methane, Earthquake and Sudden Stratospheric Warming

On the morning of March 12, 2020, peak methane levels were as high as 2902 ppb (parts per billion) at a pressure level of 469 mb (millibar, equivalent to an altitude of some 6 km (almost 20,000 feet).

What did cause this very high peak? The image on the right shows the situation at 695 mb.

High levels of methane, colored in magenta, show up over the oceans at high latitudes north, especially around Greenland and around Svalbard.

The image underneath on the right shows methane even closer to sea level, at 1000 mb. At this altitude, such magenta-colored high levels of methane only show up over an area in between Greenland and Svalbard.

It appears that these high methane levels did originate from this area. What could have triggered this?

The image below shows that an earthquake with a magnitude of 4.6 on the Richter scale hit an area in between Greenland and Svalbard on March 11, 2020, at 21:30:03 (UTC), 2020, at depth of 10 km.

It appears that the earthquake did cause destabilization of sediments at the seafloor of the Arctic Ocean in between Greenland and Svalbard, containing methane in the form of hydrates and free gas, with the destabilization resulting in the eruption of methane that subsequently reached the atmosphere.

As illustrated by the image on the right, there were strong differences in pressure in the atmosphere over Greenland on the one hand and over the Arctic Ocean on the other hand, on March 11, 2020, 21:00 UTC.

The next question is if there was something that triggered the earthquake. The image below shows a forecast for March 22, 2020, of conditions in the stratosphere at 10 hPa.

Above image shows a forecast for March 22, 2020, of temperatures as high as 6.2°C or 43.2°F and as low as -68.8°C or -91.9°F at another location at 10 hPa (Polar Vortex), with wind reaching speeds as high as 369 km/h or 229 mph.

The image on the right shows a huge temperature difference between two locations in the stratosphere on March 23, 2020, resulting in wind reaching speeds as high as 341 km/h or 212 mph.

This indicates a strong updraft, carrying huge amounts of relatively warm air from low altitudes over the Arctic up into the stratosphere.

Following a steep fall, Arctic sea ice extent was at a record low for the time of year on March 28, 2020, as illustrated by the image below.

Since the start of 2020, Arctic sea ice volume has been at a record low for the time of year, as the image on the right shows.

These conditions may have acted as a sink plunger, triggering the earthquake and destabilizing sediments at the seafloor, resulting in the methane eruptions.

More generally, the events reflect a huge and growing overall imbalance in the temperature of the atmosphere, and the added methane releases further contribute to this imbalance.

Meanwhile, sea surface temperatures off the coast of North America on March 21, 2020, were as much as 13.2°C or 23.7°F higher than 1981-2011 (at the green circle on the image on the right).

With sea ice thickness this low, it looks like there will be no buffer left to consume ocean heat that gets carried along the path of the Gulf Stream into the Arctic Ocean, which threatens to further destabilize sediments containing huge amounts of methane, as also discussed in an earlier post.

On top of this, high temperatures keep showing up over the Arctic Ocean in forecasts, as illustrated by the two forecasts below (for March 21, 2020, and for March 31, 2020).

Temperature anomaly forecast for March 21, 2020

Temperature anomaly forecast for March 31, 2020

Discussion

As said above, it appears that this M4.6 earthquake on March 11, 2020, caused destabilization of sediments at the seafloor of the Arctic Ocean in between Greenland and Svalbard.

The image on the right shows that earlier, a M5 earthquake hit an area a bit to the north, i.e. on March 3, 2020.

While not much methane showed up locally following that M5 earthquake, high methane readings were recorded elsewhere over large parts of the Arctic Ocean early March 2020, which could have resulted from destabilization along the fault line that crosses the Arctic Ocean (red line).

The next image on the right shows that earthquakes between Greenland and Svalbard over the past decade did predominantly occur on this fault line.

The high methane readings in between Greenland and Svalbard following the M4.6 earthquake could have occurred for the very reason that this earthquake hit an area outside the fault line, where sediments had until now rarely been shaken.

This could imply there could be huge amounts of methane contained in areas outside the fault line, supporting the above warning that ocean heat that gets carried along the path of the Gulf Stream into the Arctic Ocean threatens to further destabilize sediments containing huge amounts of methane. After all, such destabilization can occur as a result of higher temperatures or changes in pressure, or both.

Update

South Greenland was hit by M4.3 and M4.5 earthquakes on April 17, 2020. North Greenland was earlier hit by a M4.6 earthquake, on March 30, 2020.

Earthquakes that hit the Greenland mainland are rare. Earthquakes typically take place on or close to the faultline (red line) that goes over Iceland and extends north, running in between Greenland and Svalbard, as was the case with the M4.2 east of Greenland on April 2, 2020.

This faultline runs across the seafloor of the Arctic Ocean all the way to Russia. Multiple earthquakes hit this faultline recently, including two M4.3 eartquakes, one east of Severnaya Zemlya on April 12, 2020, and one near Tiksi on March 27, 2020.

The situation is dire and calls for immediate, comprehensive and effective action, as described in the Climate Plan.


Links

• Arctic Ocean January 2020
https://arctic-news.blogspot.com/2020/02/arctic-ocean-february-2020.html

• Seismic Events
https://arctic-news.blogspot.com/p/seismic-events.html

• Arctic Ocean February 2020
https://arctic-news.blogspot.com/2020/02/arctic-ocean-february-2020.html

• Climate Plan
https://arctic-news.blogspot.com/p/climateplan.html

M5.1 Earthquake hits Greenland Sea

An earthquake with a magnitude of 5.1 on the Richter scale hit the Greenland Sea on April 26, 2014, at 03:55:33 UTC at a depth of 10.00 km (6.21 mi). The epicenter of the earthquake is located right on the faultline that crosses the Arctic Ocean, at 73.479°N 7.974°E, some 567km (352mi) SSW of Longyearbyen, Svalbard.

[ click on image to enlarge ]

This follows four further recent earthquakes close to Svalbard or on the faultline north of Greenland, as indicated on above map. All these earthquakes struck at a depth of 10.00 km (6.21 mi).

Some of these earthquakes have also been discussed in earlier posts:
M4.6 - North of Franz Josef Land, 2014-04-13 02:12:19 UTC, also discussed in this post

M4.2 - North of Franz Josef Land, 2014-04-04 07:01:30 UTC

M4.4 - 262km NE of Nord, Greenland, 2014-04-22 10:30:23 UTC, also discussed in this post

M4.3 - 148km SSE of Longyearbyen, Svalbard, 2014-04-24 08:33:06 UTC
M5.1 - Greenland Sea, 2014-04-26 03:55:33 UTC

M4.5 - Gakkel Ridge, 2014-03-06 11:17.17.0 UTC, also discussed in this post

There have been a large number of earthquakes around Greenland since early 2014, as illustrated by the image below. This could be an indication of isostatic rebound, as also discussed in this earlier post.

[ click on image to enlarge ]

As melting of the Greenland Ice Sheet speeds up, isostatic rebound could cause earthquakes around Greenland to become stronger and occur more frequently. Earthquakes in this region are very worrying, as they can destabilize hydrates contained in the sediment under the seafloor of the Arctic Ocean. Furthermore, one earthquake can trigger further earthquakes, especially at locations closeby on the same faultline.

An uncharted 21-23rd centuries’ climate territory

by Andrew Glikson

Precis

21–23ʳᵈ centuries’ transient ocean cooling events (stadials), triggered by ice melt flow from the Greenland and Antarctic ice sheets into the adjacent oceans, herald conditions analogous in part to those of the Younger Dryas stadial (12.9–11.7 kyr) which succeeded the pre-Holocene Bölling-Allerod thermal maximum. The subsequent Younger Dryas cooling event was associated with penetration of polar air masses and ocean currents, leading to storminess, analogous to recent breaching of the weakened polar jet stream boundary, ensuing in major snow storms in North America and Europe and cooling of parts of the North Atlantic Ocean and parts of the circum-Antarctic ocean triggered by the flow of ice melt water from melting glaciers.

21–23ʳᵈ Centuries’ Stadial freeze events

IPCC climate change projections for 2100-2300 portray linear to curved temperature progressions (SPM-5). By contrast, examination of transient cooling events (stadials) which ensued from the flow of ice melt water into the oceans during peak interglacial warming events portray abrupt temperature variations (Fig. 1). The current flow of ice melt water from Greenland and Antarctica ensuing from Anthropogenic global warming is leading to regional ocean cooling in the North Atlantic near Greenland and around Antarctica (Rahmstorf et al, 2015; Hansen et al. (2016); Bronselaer et al. 2018; Purkey et al. 2018; Vernet et al. 2019) (Fig. 2). The incipient developments of ice melt-derived cold water pools in ocean regions adjacent to the large ice sheets imply portents of future stadial events such as, inexplicably, are not indicated by the predominantly linear IPCC climate projections for the 21–23ʳᵈ centuries (IPCC AR5). By contrast, as modelled by Hansen et al. (2016) and Bronselaer et al. (2018), under high greenhouse gas and temperature rise trajectories (RCP8.5), the ice meltwater flow into the oceans from the Antarctic and Greenland ice sheets would lead to cooling of large regions of the ocean, with major consequences for future climate projections. This would include the build-up of large cool ocean pools in the North Atlantic south of Greenland (Rahmstorf et al, 2015) (Fig. 2A) and around Antarctica (Fig. 2B).

Depending on different greenhouse emission scenarios (IPCC 2019; van Vuren et. al. (2011), including the CO₂ forcing-equivalents of methane (CH4) and nitrous oxide (N2O), the total CO₂–equivalent rise amounts to 496 ppm (NOAA, 2019), close to transcending the melting points of large parts of the Greenland and Antarctica ice sheets. Given the extreme rise in temperature since the mid-20th Century, where the oceans heat contents is rising, an incipient cooling of near-surface sub-Greenland and sub-Antarctic ocean regions raises the question whether incipient stadial events, perhaps analogous to the Younger Dryas stadial (Johnsen et al. 1972; Severinghaus et al. 1998), may be developing?

Interglacials, late Pleistocene and early Holocene stadial events

Stadial effects in the late Pleistocene record follow peak interglacial temperatures (Cortese et al., 2007) (Fig. 1). During the last glacial termination (LGT) stadial effects included the Oldest Dryas at ~16 kyr, the Older Dryas at ~14 kyr and the Younger Dryas at 12.9 - 11.7 kyr (Fig. 3), the latter with sharp transitions as short as 1 to 3 years (Steffensen et al., 2008), signifying a return to glacial conditions. A yet younger stadial event is represented at ~8.4 - 8.2 kyr when large-scale melting of the Laurentian ice sheet ensued in the discharge of cold water via Lake Agasiz (Matero et al. 2017; Lewis et al., 2012) into the North Atlantic Ocean. The Laurentian cooling involved temperature and CO₂ decline of ~25 ppm over ~300 years (Fig. 3B and C) and a decline of the North Atlantic Thermohaline circulation.

Figure 1. (a) Evolution of sea surface temperatures in 5 glacial-interglacial transitions recorded in
ODP 1089 at the sub-Antarctic Atlantic Ocean. Grey lines – δ¹⁸O measured on Cibicidoides plankton; 
Black lines – sea surface temperature. Marine isotope stage numbers are indicated on top of diagrams.
Note the stadial following interglacial peak temperatures (Cortese et al. 2007).
 (b) The last glacial maximum and the last glacial termination.
Olds – Oldest Dryas; Old – Older Dryas; Yd – Younger Dryas.

Greenland and Antarctica ice melt events

Oxygen isotopes (¹⁸O/¹⁹O), argon isotopes (⁴⁰Ar/³⁹Ar) and nitrogen isotopes (¹⁵N/¹⁴N) studies of Greenland ice cores (Johnsen et al. 1972; Severinghaus et al. 1998) indicate a rise in temperature to -36°C, followed by a sharp fall to -50°C (Table 1; Fig. 3A). At lower latitudes the mean temperatures drop about -2°C and 6°C (Table 1). In the southern hemisphere temperatures dropped by about -2°C in lower latitudes and about -8°C at high latitudes and (Fig. 4; Table 1) Shakun and Carlson, 2010).

Figure 2. A. The cold ocean region south of Greenland visible on NASA's 2015 global mean temperatures, the warmest year on record since 1880. Colors indicate temperature anomalies (NASA/NOAA; 20 January 2016);
B. Circum-Antarctic summer surface temperatures, showing the large Weddell Sea cold anomaly
and a seasonal warming anomaly in the Ross Sea due to upwelling of warm salty water.

Table 1.
Cooling intervals (stadial events) during late Pleistocene and early Holocene interglacial phases.

Isotopic Stage	Agemax kyr	Agemin kyr	∆tkyr	TmaxoC SST	TminoC SST	∆ToC
Stadial MIS 11-12 Ref. A	434 kyr	424 kyr	10 kyr	19.3oC SST	13.4oC SST	-5.9oC
Stadial MIS 9-10  Ref. B	346 kyr	331 kyr	5 kyr	19oC SST	13oC SST	-6oC
Stadial MIS 7-8   Ref. C	243.5 kyr	241.5 kyr	2.0 kyr	18oC SST	15.5oC SST	-2.5oC
Stadial MIS 5-6 Ref. D	136 kyr	130 kyr	6.0 kyr	19oC SST	15.2oC SST	-3.8oC
Younger Dryas stadial ice core In Greenland MIS 1-2-3  Ref. E	12.86 kyr	11.64 kyr	1.22 kyr	-36oC Greenland ice core	-50oC Greenland ice core	-14±3oC Greenland ice core
Younger Dryas at lower and mid-latitudes of the NH (Fig. 4) Ref. F	12.86 kyr	11.64 kyr	1.22 kyr			-2 to -6oC
8.3 kyr Stadial  Ref. G	8.45 kyr	8.1 kyr	0.35 kyr	-28oC CO₂=310 ppm	-30oC CO₂=275 ppm	-2.0oC

Figure 3. A. Temperature variations during the late Pleistocene to the beginning of the Younger Dryas stadial
and the onset of the Holocene, determined as proxy temperatures from ice cores of the central Greenland ice sheet;
B. The ~8.2 kyr stadial event in a coupled climate model (Wiersma et al. 2011);
C. Reconstructed CO₂ concentrations for the interval between ~8,700 and ~6,800 B.P. 
based on CO₂ extracted from air in Antarctic ice of Taylor Dome (Wagner et al. 2002).

Figure 4. Magnitude of late Holocene glacial-interglacial temperature changes in relation to latitude.
Black squares are the Northern Hemisphere (NH), gray circles the
Southern Hemisphere (SH) (Shakun and Carlson, 2010)

Antarctic ice melt dynamics

Circum-Antarctic surface air temperatures, precipitation and sea-ice cover (Bronselaer et al. (2018), including testing the effects of ice-shelf melting, identifies penetration of relatively warm circumpolar deep water below 400 m into the grounding line underlying the ice shelf (Figs 5, 6A). The flow of ice melt water into the adjacent ocean forms an upper cold water layer away from ice shelf areas (Figure 6B). These authors indicate the flow of ice-sheet meltwater results in a decrease of global atmospheric warming, shifts rainfall northwards, and increases sea-ice area and offshore subsurface Antarctic Ocean temperatures.

Figure 5. Schematic circulation and water masses in the Antarctic continental shelf (Purkey et al., 2018) displaying layering of the sub-Antarctic into a cold ice melt-derived upper layer (-2.1°C) overlying a warmer water zone (-1.0°C) which acts as a source of modified warm water penetrating the grounding zone of the glacial ice shelf.

Figure 6. A. The grounding zone where the bedrock-grounded ice sheet transits to a freely floating ice shelf over several km. The floating ice shelf changes in elevation in response to tides, atmospheric air pressure and oceanic processes. B. The Helium (∆He% - Temperature proxy) profile in the Amundsen Sea. The black dots indicate the sampling depth, and the grey dotted lines indicate the isopycnal (density) lines. The shelf break is located at about ∼280 km).

In turn warmer salty water from the circum-polar deep water (CDW) from the circum-Antarctic current can penetrate below the cold off-shelf layer, as is the case in the Weddell Sea Gyre (Figures 5, 6 and 7).

Figure 7. Penetration of relatively warm and salty water from the circum-Antarctic current below the cold off-shelf surface layer of the Weddell Sea Gyre.

Global stadial cooling events

Hansen et al. (2016) suggest that, depending on ice melt rates of the polar ice sheets, transient cooling events (stadials) can be expected to develop at times dependent on the rates of ice melt (Fig. 8). The model is consistent with a slowdown of the Atlantic Meridional Ocean Circulation (AMOC) (Weaver et al. 2012) and the exceptional growth of a cold water region southeast of Greenland, (Rahmstorf et al, 2015). These authors suggest stadial cooling of about -2°C lasting for several decades (Fig. 8B), depending on ice melt rates, can affect temperatures in Europe and North America.

Figure 8. A. Model surface air temperature (°C) change in 2055–2060 relative to 1880–1920 for modified forcings.
B. Surface air temperature (°C) relative to 1880–1920 for several ice melt scenarios.

According to Bronselaer et al. (2018) temporal evolution of the global-mean surface-air temperature (SAT) shows meltwater-induced cooling translates to a reduced rate of global warming (Fig. 9), with a maximum divergence between standard models and models which include the effects of meltwater induced cooling of 0.38 ± 0.02°C in 2055. The SAT response shows the effect of ice meltwater becomes weaker as the ocean becomes more stratified as a result of both moderate to deep level warming and cooling/freshening at the surface (Fig. 6B). As stated by the authors “We demonstrate that the inclusion in the model of ice-sheet meltwater reduces global atmospheric warming, shifts rainfall northwards, and increases sea-ice area”, and “Antarctic meltwater is therefore an important agent of climate change with global impact, and should be taken into account in future climate simulations and climate policy.”

Figure 9. A. 2080–2100 meltwater-induced sea-air temperature anomaly relative to the standard RCP8.5 ensemble. Hatching indicates where the anomalies are not significant at the 95% level.
B. Time series of the global-mean sea-air temperature (SAT) anomaly relative to the 1950–1970 mean.
Orange shows the standard ensemble and blue shows the meltwater-included ensemble. Solid lines show ensemble means, the dark shading shows the 95% uncertainty in the mean and the light shading shows the full ensemble spread of 20-year means. The green bar indicates the period when the standard and meltwater ensembles diverge.

Based on the paleoclimate record, global warming and rates of melting and surface cooling around parts of Antarctica and the North Atlantic (Fig. 2) would determine the future climate of large parts of Earth. Transient stadial cooling events, inherently associated with meters-scale sea level rise, would result in increased temperature polarities between subpolar and tropical latitudes, leading to storminess where polar-derived and tropical-derived air masses and ocean currents collide. Regional to global stadial cooing would, in principle, last as long as ice sheets remain. Once the large ice sheets are exhausted a transition takes place toward tropical Miocene-like and even Eocene-like conditions about 4 to 5 degrees Celsius warmer than Holocene climate conditions, which allowed agriculture and thereby civilization to emerge.

Andrew Glikson

Dr Andrew Glikson
Earth and Paleo-climate scientist
ANU Climate Science Institute
ANU Planetary Science Institute
Canberra, Australia

Books:
The Asteroid Impact Connection of Planetary Evolution
http://www.springer.com/gp/book/9789400763272
The Archaean: Geological and Geochemical Windows into the Early Earth
http://www.springer.com/gp/book/9783319079073
Climate, Fire and Human Evolution: The Deep Time Dimensions of the Anthropocene
http://www.springer.com/gp/book/9783319225111
The Plutocene: Blueprints for a Post-Anthropocene Greenhouse Earth
http://www.springer.com/gp/book/9783319572369
Evolution of the Atmosphere, Fire and the Anthropocene Climate Event Horizon
http://www.springer.com/gp/book/9789400773318
From Stars to Brains: Milestones in the Planetary Evolution of Life and Intelligence
https://www.springer.com/us/book/9783030106027
Asteroids Impacts, Crustal Evolution and Related Mineral Systems with Special Reference to Australia
http://www.springer.com/us/book/9783319745442