Sentences with phrase «ice sheet response times»

Second, the abstract admits that, «Pleistocene climate oscillations yield a fast - feedback climate sensitivity of 3 ± 1 °C for a 4 W m − 2 CO2 forcing if Holocene warming relative to the Last Glacial Maximum (LGM) is used as calibration, but the error (uncertainty) is substantial and partly subjective» and also «Ice sheet response time is poorly defined».

Ice sheet response time is poorly defined, but we show that the slow response and hysteresis in prevailing ice sheet models are exaggerated.

Not exact matches

More specifically, can one define the response time of a particular ice sheet?

... Polar amplification explains in part why Greenland Ice Sheet and the West Antarctic Ice Sheet appear to be highly sensitive to relatively small increases in CO2 concentration and global mean temperature... Polar amplification occurs if the magnitude of zonally averaged surface temperature change at high latitudes exceeds the globally averaged temperature change, in response to climate forcings and on time scales greater than the annual cycle.

[this is useful, the pre-ice age era, ~ 2.5 — 3.6 million years ago, last time CO2 levels were as high as today] In response to Pliocene climate, ice sheet models consistently produce near - complete deglaciation of the Greenland ice sheet (+7 m) and West Antarctic ice sheet (+4 m) and retreat of the marine margins of the Eastern Antarctic ice sheet (+3 m)(Lunt et al., 2008; Pollard and DeConto, 2009; Hill et al., 2010), altogether corresponding to a global mean sea level rise of up to 14 m.

[Response: Here's a simple back - of - envelope consideration for the future: if the Greenland ice sheet melts completely over the next ~ 1,000 years (Jim Hansen argues in the current Climatic Change that the time scale could be centuries), this would contribute an average flux of ~ 0.1 Sv of freshwater to the surrounding ocean.

«This uncertainty is illustrated by Pollard et al. (2015), who found that addition of hydro - fracturing and cliff failure into their ice sheet model increased simulated sea level rise from 2 m to 17 m, in response to only 2 °C ocean warming and accelerated the time for substantial change from several centuries to several decades.»

Of course I can not prove that my choice of a ten - year doubling time for nonlinear response is accurate, but I am confident that it provides a far better estimate than a linear response for the ice sheet component of sea level rise under BAU forcing.

To quote «Proof is obtained by considering the contrary: ice sheet forcing approximately 3W / m ^ 2 and a 5 kyr timing gap between forcing and response, as appears to be the case at Termination IV (figure 2c), is 15,000 W yr / m ^ 2, enough to warm the upper kilometre of the ocean by approximately 160 C» (pdf page 7) This is his justification for modifying the data - not my «characterization» of what he said.

The millennial (500-2000 year) time scale of deep ocean ventilation affects the time scale for natural CO2 change and thus the time scale for paleo global climate, ice sheet, and sea level changes, but this paleo millennial time scale should not be misinterpreted as the time scale for ice sheet response to a rapid large human - made climate forcing.

This thin ice cap is very different from the Greenland Ice Sheet where the enormous thickness gives it a very slow response time and the type of process you are suggesting can operaice cap is very different from the Greenland Ice Sheet where the enormous thickness gives it a very slow response time and the type of process you are suggesting can operaIce Sheet where the enormous thickness gives it a very slow response time and the type of process you are suggesting can operate.

A lowering of atmospheric carbon dioxide levels near the beginning of this time period occurred in response to the rise of land plants and likely cooled Earth, but the rapid growth of extensive Gondwanan ice sheets was delayed for tens of millions of years, until the Late Mississippian.»

To avoid long response times in extreme climates, today's ice sheets are assigned surface properties of the tundra, thus allowing them to have a high albedo snow cover in cold climates but darker vegetation in warm climates.

This millennial carbon cycle time scale should not be misinterpreted as the ice sheet time scale for response to a rapid human - made climate forcing.

We argue that ice sheets in contact with the ocean are vulnerable to non-linear disintegration in response to ocean warming, and we posit that ice sheet mass loss can be approximated by a doubling time up to sea level rise of at least several meters.

Examples: Weertman (1976a)(Northwestern Univ., IL, and the U.S. Army Cold Regions Research and Engineering Laboratory, Hanover, NH); note also his pioneering calculation of ice sheet buildup and shrinkage times, Weertman (1964); Sergin (1979)(Laboratory for Mathematical Modeling of the Climate, Pacific Institute of Geography of Academy of Sciences, Vladivostok, but written while visiting NCAR, Boulder, CO); Budd and Smith (1981)(Meteorology Dept., U. Melbourne); as a perhaps more typical example, Young (1979)(Antarctic Division, Dept. of Science and Technology, Kingston, Tasmania) conservatively showed a response time of perhaps 20,000 years; an especially influential model involving ice sheet buildup delay was Imbrie and Imbrie (1980); a good review is Budd (1981).

The Greenland and Antarctic ice sheets have much larger masses and consequently much longer time constants, but there is already observational evidence of nonlinear response.

For the ice sheets the answer is probably no (but experts on the subject might have a better idea), but for the overturning circulation or the ecosystem changes, the answer is probably yes — i.e. a slower rate of warming could lead to a different response (allowing time for ocean mixing to mitigate the effects, or adaptation of species to the new conditions).