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.


References

- South Greenland ice-sheet collapse during Marine Isotope Stage 11, Reyes et al. (2014)
http://www.nature.com/nature/journal/v510/n7506/full/nature13456.html

- Nonsustainable groundwater sustaining irrigation: A global assessment, Yoshihide Wada et al. (2012)
http://onlinelibrary.wiley.com/doi/10.1029/2011WR010562/abstract

- Groundwater Depletion Linked to Rising Sea Levels
http://www.waterworld.com/articles/2010/11/groundwater-depletion-linked-to-rising.html

- 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)
http://www.tandfonline.com/doi/abs/10.1080/01490419.2010.491029

- Feedbacks in the Arctic
http://climateplan.blogspot.com/p/feedbacks.html

- How many deaths could result from failure to act on climate change? (2014)
http://arctic-news.blogspot.com/2014/05/how-many-deaths-could-result-from-failure-to-act-on-climate-change.html

Post by Sam Carana.

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
wikipedia.org/wiki/Albedo

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.

Sources:

1. Albedo - Wikipedia
   wikipedia.org/wiki/Albedo
2. Albedo change in the Arctic
   arctic-news.blogspot.com/2012/07/albedo-change-in-arctic.html
3. Carbon dioxide enhances fragility of ice crystals
   by Zhao Qin and Markus J Buehler 2012
   Journal of Physics D: Applied Physics Volume 45 Number 44
   iopscience.iop.org/0022-3727/45/44/445302
4. Carter, P., Northern hemisphere loss of snow and ice albedo cooling
   youtube.com/watch?v=-18xi1hQXNc
5. Flanner et al. (2011a), Radiative forcing and albedo feedback from the Northern Hemisphere cryosphere between 1979 and 2008, Flanner et al.
   nature.com/ngeo/journal/v4/n3/full/ngeo1062.html
6. Flanner et al. (2011b), Presentation October 27, 2011, WCRP Open Science Conference
   wcrp-climate.org/conference2011/orals/B11/Flanner_B11.pdf
7. Glaciers Cracking - Press Release
   cms.iopscience.iop.org/alfresco/d/d/workspace/SpacesStore/bf99f6c7-1386-11e2-bc48-4d5160a0f0b4/Glaciers_cracking_press_release
8. IPCC 2007a, Climate Change 2007: Working Group I: The Physical Science Basis
   ipcc.ch/publications_and_data/ar4/wg1/en/ch4s4-1.html
   ipcc.ch/publications_and_data/ar4/wg1/en/ch4s4-2.html
9. IPCC 2007b, Changes in Atmospheric Constituents and in Radiative Forcing, IPCC (2007)
   ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter2.pdf
10. NASA, 2005 (at Archive.org)
    archive.org/details/albedo_ceres_mar05
11. NSIDC, NOAA - Northern Hemisphere snow and ice map
    nsidc.org/data/g02156.html