Global Warming Art:Sea Level Rise Explorer Description

From Global Warming Art

The following is the description page for the Sea Level Rise Explorer. Please visit that page to see the full content.



Description

The map shown above allows you to explore the regions of the Earth that are most vulnerable to sea level rise.

As with other Google Maps, you can click-and-drag the window to scroll or double click to zoom.

Potential for Sea Level Rise

Sources of potential sea level rise
Thermal expansion of the oceans 0.2-0.4 m per degree C[1]
Mountain glaciers and ice caps 0.15-0.37 m[2]
Greenland Ice Sheet 7.3 m[3]
West Antarctica Ice Sheet 5 m[4]
East Antarctic Ice Sheet 52 m[4]

As global warming progresses, sea level is expected to rise primarily due to the melting of continental ice sheets in Greenland and Antarctica. However, the ultimate amount of flooding is highly uncertain. A full deglaciation of both poles would raise sea level as much as ~65 meters (210 feet), though it is very likely that the ultimate sea level rise will be only a fraction of this possible total.

During the twentieth century, sea level rose 20 cm. It is predicted that sea level rise will accelerate during the twenty-first century, but many model predictions still foresee a sea level rise of less than 1 additional meter by 2100. The greatest uncertainty in these predictions is the role of ice streams and iceberg calving from the major ice sheets. Current models are unable to predict the degree by which ice streams may accelerate in response to warming.[2] By one estimate, the glacial outflow from Greenland increased 200% from 1996 to 2005.[5] This increase in Greenland's outflow, if sustained, would add only ~3.5 cm to sea level by 2100. However, since this large increase was apparently triggered by relatively mild warming, the IPCC is unable to rule out dramatic further increases in outflow.[2] A further ten-fold increase in glacial outflow and corresponding increases in the glacial outflow of Antarctica could effectively double the total mass loss through 2100. Even so, the likely scenarios for twenty-first century sea level rise due to unrestrained global warming remain less than 2 m.

Sea Level Rise Risk for Sea Level Rise[6]
By the year 2100 By the year 3000 Beyond the year 3000
0-1 m High Virtually Certain Virtually Certain
1-2 m Low to Moderate Virtually Certain Virtually Certain
2-6 m Very Low High High
6-12 m None Low to Moderate Moderate
12-20 m None Low Low to Moderate
20-65 m None Very Low Low

However, even if global temperatures stabilize in 2100, the full magnitude of sea level rise is expected to take far longer to develop. By one estimate, carbon dioxide stabilization at 1100 ppmv (four times pre-industrial levels) would still only result in a 60% mass loss in Greenland after 1000 years of melting, and an additional 2000 years to melt the remainder.[7] (This estimate does not include the potential impact of ice stream acceleration.) The sheer size of the ice sheets involved essentially guarantee that the melting component of sea level rise will progress slowly.

Regardless of the time scale involved, an analogy to the previous interglacial suggests that a few degrees Celsius of sustained warming can cause enough melting to raise sea level 4-6 m before the ice sheets reach equilibrium.[8] This level of warming is likely to be achieved or even exceeded by 2100 in the absence of intervention to combat climate change, though as above, it would take far longer to realize the full sea level change.

Accuracy of Maps

The sea level data appearing in my maps is based primarily on version 2 of NASA's Shuttle Radar Topography Mission (SRTM), with post-processing by CGIAR to fill-in voids using data from other sources. The underlying data has a horizontal resolution of 90 m at the equator. Over the entire globe, the absolute vertical error is estimated as less than 9 m at 90% confidence, with substantial regions having an error of 5 m or less at 90% confidence.[9][10] No satellite-based elevation dataset has accuracy better than this. The largest errors are primarily associated with complex, rapidly varying terrain. Since coastal regions tend to flat and the ocean's surface provides a calibration target for the radar system, one can usually expect that near shore elevations will be somewhat more accurate than the average. However, it is reasonable to treat the smallest scale fluctuations at high magnification with a healthy dose of scepticism.

One of the limitations of the SRTM data is that radar beam sees only the uppermost surface in a given area and this may not reflect the ground level. This causes the data set to overestimate elevation in densely forested or urbanized areas. Consequently, cities like Manhattan appear to have significantly greater average elevation than one would perceive at street level. In addition, the radar system may underestimate the elevation of deserts due to poor radar reflection from dry sand.[10] Lastly, there are a number of holes in the SRTM data that CGIAR filled with lower quality data. Some of these fills will contain noticably defects (such as parts around Rhode Island).

The SRTM data are limited to a region of 60 S to 60 N latitude. Outside this region, sea level information was extracted from the Global Land One-km Base Elevation (GLOBE) Project which has a horizontal resolution of ~1 km at the equator and is often characterized by vertical errors of +/- 30 m. Obviously this resolution is quite crude and so data at high latitudes should be taken as a rough estimate of actual elevation. In addition, the stretching of the Mercator Projection near the poles increases the apparent distortion.

Lastly, since these maps don't include any information regarding tides, storm surges, or other coastal effects, they provide only a partial picture of how vulnerable a given terrain may be to sea level rise.

Though these data are amongst the best available for the purpose of estimating sea level rise effects, it should also be clear that their small scale accuracy is limited. Hence, one should view these maps as rough estimations of how sea level rise may affect coastal areas and not rely on them too heavily.

Related Materials

References

  1. ^ [abstract] [DOI] Knutti, Reto and Thomas F. Stocker (2000). "Influence of the Thermohaline Circulation on Projected Sea Level Rise". Journal of Climate 13 (12): 1997-2001. 
  2. ^ a b c [full text] Intergovernmental Panel on Climate Change (2007a). Climate Change 2007 - The Physical Science Basis: Contribution of Working Group I to the Fourth Assessment Report of the IPCC. Cambridge: Cambridge University Press. ISBN 978 0521 88009-1. 
  3. ^ [abstract] Bamber J.L., R.L. Layberry, and S.P. Gogenini (2001). "A new ice thickness and bedrock data set for the Greenland ice sheet". JGR Atmospheres 106 (D24): 33773-33780. 
  4. ^ a b [abstract] Lythe, Matthew B., David G. Vaughan, and the BEDMAP Consortium (2001). "BEDMAP: A new ice thickness and subglacial topographic model of Antarctica". Journal of Geophysical Research 106 (B6): 11335–11351. 
  5. ^ [abstract] [DOI] Rignot, Eric and Pannir Kanagaratnam (2006). "Changes in the Velocity Structure of the Greenland Ice Sheet". Science 311 (5763): 986-990. 
  6. ^ These descriptions reflect the qualitative opinions of the author based on a review of the literature.
  7. ^ [abstract] [DOI] J. K. Ridley, P. Huybrechts, J. M. Gregory, J. A. Lowe (2005). "Elimination of the Greenland Ice Sheet in a High CO2 Climate". Journal of Climate 18 (17): 3409–3427. 
  8. ^ [abstract] [DOI] Overpeck, Jonathan T., Bette L. Otto-Bliesner, Gifford H. Miller, Daniel R. Muhs, Richard B. Alley, Jeffrey T. Kiehl (2006). "Paleoclimatic Evidence for Future Ice-Sheet Instability and Rapid Sea-Level Rise". Science 311 (5768): 1747-1750. 
  9. ^ [abstract] [full text] [DOI] Farr, Tom G. and many others (2007). "The Shuttle Radar Topography Mission". Reviews of Geophysics 45: RG2004. 
  10. ^ a b [full text] Rodriguez, E., C.S. Morris, J.E. Belz, E.C. Chapin, J.M. Martin, W. Daffer, S. Hensley (2005). An assessment of the SRTM topographic products, Technical Report JPL D-31639. Pasadena, California: Jet Propulsion Laboratory.