Showing posts with label glaciers. Show all posts
Showing posts with label glaciers. Show all posts

Wednesday, January 28, 2015

Rain Storms Devastate Arctic Ice And Glaciers

by Veli Albert Kallio

The Norwegian Svalbard Islands are located just few hundred miles from the North Pole. It is a unique environment for glaciers: Here glaciers can survive almost at sea level. This means that ice is constantly brushed by thick low-altitude air, which also dumps increasinlgy rain instead of snow.

As a result of high ocean temperatures and of precipitation nowadays falling as rain for months, the melting of these glaciers now occurs 25 times faster than just some years ago.

This also spells bad news for Northern Greenland's low lying glaciers, which will face increasing summertime flash floods as the Arctic Ocean becomes ice free and warms up, and as precipitation falls in the form of rain, rather than snow.

Sea surface temperature of 17.5°C, west of Svalbard
click on image to enlarge
Last summer, for example, sea water west of the Svalbard reached +18C, which is perfect for swimming - but extremely bad for the cold glaciers on shore which mop up the warm moisture and rainfall from the warmed up ocean.

Flash floods falling on glacier soften the compacted snow very rapidly to honeycombed ice that is exceedingly watery and without any internal strength.

Such ice can collapse simply under its own weight and the pulverised watery ice in the basin forms a near frictionless layer of debris.

Darkening of the melting ice also hastens its warming and melting.

Aggressively honeycombed glacier ice floating on meltwater lake in nearby Iceland.   Image credit: Runólfur Hauksson

click on image to enlarge

Changes to the Jet Streams

As the Arctic continues to warm, the temperature difference between the equator and the Arctic declines. This slows down the speed at which the polar vortex and jet streams circumnavigate the globe and results in more wavier jet streams that can enter and even cross the Arctic Ocean and can also descend deep down over the continents, rather than staying between 50 and 60 degrees latitude, where the polar jet streams used to be (as discussed in a recent post).

Such deep descent over continents can cause very low temperatures on land, while at the same time oceans remain warm and are getting warmer, so the temperature difference between land and ocean increases, speeding up the winds between continents. On January 9, 2015, jet streams reached speeds between continents as high as 410 km/h (255 mps), as shown on above image. Also note the jet stream crossing the Arctic Ocean.

Faster winds means more water evaporation, and warmer air holds more water vapor, so this can result in huge rainstorms that can rapidly devastate the integrity of the ice.

[image and text in yellow panels by Sam Carana]


I suspect that climatically-speaking we are currently entering a methane-driven Bøllinger warming state with the Northern Cryosphere now entering a phase of rapid warming and melting of anything frozen (snow, sea ice, permafrost and sea bed methane clathrates).

This will be rapidly followed by a Heindrich Iceberg Calving event when the warmed and wet ice sheet in Greenland gives away to its increased weight (due to excessive melt water accumulation within and beneath the ice sheet).

This dislodges the ice sheet’s top, due to accumulation of “rotten ice” (honeycombed, soft ice with zero internal strength) at the ice sheet’s base and perimeters.

A huge melt water pulse to the ocean ensues with Jōkullhaups and ice debris loading the ocean with vast amounts of cold fresh water.

Within weeks an immense climatological reversal then occurs as the ocean gets loaded up with ice debris and cold water leading to the Last Dryas cooling and to world-wide droughts.

This loading of the ocean with ice and water leads to severe climatic flop, as the ocean and atmosphere cool rapidly and as falling salinity and sea water temperature briefly reverse all of the current Bøllinger warming, until the climatic forcing of the greenhouse gases again takes over the process, in turn leading to a new melt water pulse as another ice sheet or shelf disintegrates by the next warming.

Today’s rapid melt water lake formation in Greenland and the ultra-fast melting of glaciers are suggestive of near imminent deglaciation process in the Arctic.

Germany’s and Japan’s recent decisions to remove all their nuclear reactors from the sea sides may prove their worth sooner than many think in the far more conservative US and UK where “glacial speed” still means “eons of time”. Good luck UK/US!

I think cold 'Dryases' are not real Ice Ages, but hiatuses in a progressive melting process which results from changes in sea water salinity and temperature due to increases of meltwater and ice debris runoff from continental snow and ice that melt. As ocean gets less saline and colder the sea ice and snow cover temporarily grows.

But in the long run the greenhouse gas forcing and ocean wins and the warmth and melting resumes until the next big collapse of ice shelf and/or ice sheet. Hence there are meltwater pulses (such as 1a, 1b, 1c) and Heindrich Ice Berg Calving surges (2, 1, 0 - the last one being also called "Younger Dryas" as the Arctic Dryas octopetala grew in South once again after Ice Ages).

The next cooling from collapse of Greenland ice dome would be Heindrich Minus One as the zero has already been allocated to Younger Dryas ice berg surge. Here is an article worth reading on this risk. In Antarctica we see currently (already) a sea ice growth hiatus driven by increased runoff of melt water and ice debris from the continent and its surrounding ice shelves that are rapidly disintegrating.

Abrupt climate change happened in just one year

A 2008 study by Achim Brauer et al. of lake sediments concluded that abrupt increase in storminess during the autumn to spring seasons, occurring from one year to the next at 12,679 yr BP. This caused abrupt change in the North Atlantic westerlies towards a stronger and more zonal jet, leading to deglaciation.

A 2009 study by Jostein Bakke et al. confirmed that increased flux of fresh meltwater to the ocean repeatedly resulted in the formation of more extensive sea ice that pushed the jet south once more, thus re-establishing the stadial state. Rapid oscillations took place until the system finally switched to the interglacial state at the onset of the Holocene.


- An abrupt wind shift in western Europe at the onset of the Younger Dryas cold period, Brauer et al.

- Rapid oceanic and atmospheric changes during the Younger Dryas cold period, Bakke et al.

Tuesday, July 29, 2014

More than 2.5m Sea Level Rise by 2040?

A warming period more than 400,000 years ago pushed the Greenland ice sheet past its stability threshold (which may have been no more than several degrees above pre-industrial temperatures). This resulted in a nearly complete deglaciation of southern Greenland, raising global sea levels some 4.5-6 meters, found a recent study by Reyes et al. Due to melting elsewhere, global mean sea level then was 6 to 13 metres above the present level. Indeed, melting of the entire West Antarctic Ice Sheet can add a further 6-meter rise in sea levels. If the East Antarctic Ice Sheet (EAIS) were to melt as well, sea levels would rise by around 70 metres.

Sea level is now rising by 3.1mm (0.122 inch) per year. Much of this rise is due to rising temperatures, but there are also other factors. One quarter of the rise results from groundwater depletion, while run off from melting ice and glaciers adds another quarter and the remainder is attributed to thermal expansion of sea water. Furthermore, as temperatures rise, feedbacks start to kick in, e.g. the kinetic energy from stronger waves and more intense storms can speed things up.

Clearly, a rapid multi-meter rise would be devastating as it would flood many coastal cities, as well as much of the land now used to grow food. By how much have sea levels been rising recently and how fast can they be expected to rise in the near future?
NASA image, data by the JPL PODAAC, in support of the NASA's MEaSUREs program.
Sea levels have risen by some 60 mm over the past 20 years, as above NASA image shows, which has a linear trendline added. The question is whether a linear trendline is the most appropriate trendline, given that it suggests that a similar rise could be expected over the next 20 years. A polynomial trendline appears to fit the data better, as the animation below shows.

Such a polynomial trendline, however, points at a similar rise (of some 50 mm) in just four years time, with an even more steeper rise to follow, as illustrated by the image below.

And indeed, such a rise doesn't slow down there. A polynomial trendline applied to the data points at a sea level rise of more than 2.5 m (8.2 ft) by the year 2040.

The image below gives an idea of what a sea level rise of six feet (1.829 m) would do to the City of New York. Of course, this is only the sea level rise. Storm surge would come on top of this, as discussed at Ten Dangers of Global Warming.

So, what would be more appropriate, to expect sea levels to continue to rise in a linear way, or to take into account feedbacks that could speed things up? Where such feedbacks could lead to is illustrated by the image below.
[ from: How many deaths could result from failure to act on climate change? click on image to enlarge ]
This calls for comprehensive and effective action, as discussed at the Climate Plan blog.


- South Greenland ice-sheet collapse during Marine Isotope Stage 11, Reyes et al. (2014)

- Nonsustainable groundwater sustaining irrigation: A global assessment, Yoshihide Wada et al. (2012)

- Groundwater Depletion Linked to Rising Sea Levels

- Assessment of the Jason-2 Extension to the TOPEX/Poseidon, Jason-1 Sea-Surface Height Time Series for Global Mean Sea Level Monitoring, Beckley et al. (2010)

- Feedbacks in the Arctic

- How many deaths could result from failure to act on climate change? (2014)

Sunday, October 14, 2012

Glaciers cracking in the presence of carbon dioxide

Northern Hemisphere snow and ice map , October 14, 2012 (credit: NSIDC, NOAA)

Snow covers more than 33% of lands north of the equator from November to April, reaching 49% coverage in January. The role of snow in the climate system includes strong positive feedbacks related to albedo and other, weaker feedbacks related to moisture storage, latent heat and insulation of the underlying surface, which vary with latitude and season (IPCC, 2007a8).

Albedo or reflectivity of surfaces
Ice caps and glaciers cover 7% of the Earth—more than Europe and North America combined—and are responsible for reflecting 80–90% of the Sun’s light rays that enter our atmosphere and maintain the Earth’s temperature7. They are also a natural carbon sink, capturing a large amount of carbon dioxide7.

Snow and ice on the Northern Hemisphere has a cooling effect of 3.3 watts per square meter, peaking in May at ~ 9 watts per square meter. Snow and ice on the Northern Hemisphere has declined over the years and is now reflecting 0.45 watts less energy per square meter than it did in 1979 (Flanner, 2011). As discussed in Albedo change in the Arctic, this compares to warming of 1.66 watts per square meter for the net emission by people (IPCC, 2007b9).

A recent press release7 announced that researchers from the Massachusetts Institute for Technology have shown that the material strength and fracture toughness of ice are decreased significantly under increasing concentrations of carbon dioxide molecules, making ice more fragile and making ice caps and glaciers more vulnerable to cracking and splitting into pieces.

“If ice caps and glaciers were to continue to crack and break into pieces, their surface area that is exposed to air would be significantly increased, which could lead to accelerated melting and much reduced coverage area on the Earth,” said lead author of the study Professor Markus Buehler.

Buehler, along with his student and co-author of the paper, Zhao Qin, used a series of atomisticlevel computer simulations to analyse the dynamics of molecules to investigate the role of carbon dioxide molecules in ice fracturing, and found that carbon dioxide exposure causes ice to break more easily.

Notably, the decreased ice strength is not merely caused by material defects induced by carbon dioxide bubbles, but rather by the fact that the strength of hydrogen bonds—the chemical bonds between water molecules in an ice crystal—is decreased under increasing concentrations of carbon dioxide. This is because the added carbon dioxide competes with the water molecules connected in the ice crystal.

It was shown that carbon dioxide molecules first adhere to the crack boundary of ice by forming a bond with the hydrogen atoms and then migrate through the ice in a flipping motion along the crack boundary towards the crack tip.

The carbon dioxide molecules accumulate at the crack tip and constantly attack the water molecules by trying to bond to them. This leaves broken bonds behind and increases the brittleness of the ice on a macroscopic scale7.

A drop of as little as 1% in Earth’s albedo corresponds with a warming roughly equal to the effect of doubling the amount of carbon dioxide in the atmosphere, which would cause Earth to retain an additional 3.4 watts of energy for every square meter of surface area (NASA, 200510; Flanner et al., 2011b6).

Below, a video by Dr. Peter Carter4, showing loss of snow and ice albedo on the Northern Hemisphere from 1997 to 2009, using NOAA images, and also showing the relationship to global food security and Arctic methane.