Sentences with phrase «glacial ice forced»
Scientists have suggested that similar formations in Sweden formed when the immense weight of glacial ice forced sand and other loose material into fissures in underlying rocks.
http://www.sciencemag.org/ Not exact matches
These forces occur on Earth in glacial ice as it flows due to gravity, and in space as icy satellite bodies, such as the moons of Jupiter and Saturn, respond to tidal forces from their parent bodies.
It seems that after the climate cooled during the last glacial period, disappearing habitat inland forced brown bears toward the coasts, where they encountered polar bears shifted there by British - Irish ice sheets.
The Laurentide Ice Sheet, the major driving force for ocean circulation during the glacials, has also disappeared.
During the last glacial maximum, Wiens explained, the weight of the ice bent the Earth's crust, forcing the plastic rock in the upper layer of the Earth's mantle to flow away from the loaded region.
«the last glacial period is a good example of a large forcing (~ 7 W / m ^ 2 from ice sheets, greenhouse gases, dust and vegetation) giving a large temperature response (~ 5 ºC) and implying a sensitivity of about 3ºC (with substantial error bars).»
As we have discussed previously, the last glacial period is a good example of a large forcing (~ 7 W / m2 from ice sheets, greenhouse gases, dust and vegetation) giving a large temperature response (~ 5 ºC) and implying a sensitivity of about 3ºC (with substantial error bars).
In some sense, the search for a theory of glacial - interglacial cycles amounts to a search for the «rectifier» which turns the modulation of the amplitude of the seasonal forcing into a rectified signal in global ice volume.
On the studies of sensitivity based on the last glacial maximum, what reduction in solar forcing is used based on the increased Albedo of the ice - sheets, snow and desert.
26 Paul W asked, «On the studies of sensitivity based on the last glacial maximum, what reduction in solar forcing is used based on the increased Albedo of the ice - sheets, snow and desert.
Does this process run freely, or is it synchronized to some other forcing — like Huybers & Wunsch propose for ice ages in «Obliquity pacing of the late Pleistocene glacial terminations»?
Although the primary driver of glacial — interglacial cycles lies in the seasonal and latitudinal distribution of incoming solar energy driven by changes in the geometry of the Earth's orbit around the Sun («orbital forcing»), reconstructions and simulations together show that the full magnitude of glacial — interglacial temperature and ice volume changes can not be explained without accounting for changes in atmospheric CO2 content and the associated climate feedbacks.
«the last glacial period is a good example of a large forcing (~ 7 W / m ^ 2 from ice sheets, greenhouse gases, dust and vegetation) giving a large temperature response (~ 5 ºC) and implying a sensitivity of about 3ºC (with substantial error bars).»
At the last glacial maximum (20,000 yrs ago), forcings by ice sheets, vegetation, greenhouse gases and dust loading are estimated to be around -7 W / m2, and that sustained a climate 5 to 6 degrees cooler than present.
On the studies of sensitivity based on the last glacial maximum, what reduction in solar forcing is used based on the increased Albedo of the ice - sheets, snow and desert.
[Response: All forcings are calculated by changing the boundary conditions (in this case the distribution of glacial ice, and looking to see what the change in net radiation is while keeping everything else constant.
[Response: To pre-empt some mutual incomprehension, note that industrial CO2 rises are certainly an anthropgenic forcing and not a response (see here and here), but clearly CO2 changes over glacial - interglacial cycles is both a response (to Milankovitch - driven changes) and a forcing (since the additional radiative forcing from CO2 is about a third of that needed to keep the ice ages as cold as they are — see here).
Once the ice reaches the equator, the equilibrium climate is significantly colder than what would initiate melting at the equator, but if CO2 from geologic emissions build up (they would, but very slowly — geochemical processes provide a negative feedback by changing atmospheric CO2 in response to climate changes, but this is generally very slow, and thus can not prevent faster changes from faster external forcings) enough, it can initiate melting — what happens then is a runaway in the opposite direction (until the ice is completely gone — the extreme warmth and CO2 amount at that point, combined with left - over glacial debris available for chemical weathering, will draw CO2 out of the atmosphere, possibly allowing some ice to return).
Redistribution of C has acted as a positive feedback to orbitally - forced glacial - interglacial variations (ice ages)-- but this depends on some particulars and isn't necessarily a general feature applicable to every geologic age -LRB-?).
Other forcings, including the growth and decay of massive Northern Hemisphere continental ice sheets, changes in atmospheric dust, and changes in the ocean circulation, are not likely to have the same kind of effect in a future warming scenario as they did at glacial times.
article, Hansen estimates that the radiative forcing from all greenhouse gases together (glacial - interglacial) is -2.6 + / - 0.5 W / m ^ 2, and ice sheet albedo is -3.5 + / -1 W / m ^ 2.
We assess atmospheric versus oceanic influences on glacial discharge at this location, using analyses of diatom geochemistry to reconstruct atmospherically forced glacial ice discharge and diatom assemblage ecology to investigate the oceanic environment.
* It would take only a small further reduction in climate forcing (less long - lived GHGs or whatever) to yield more ice during the glacial phase of glacial - interglacial oscillations.
From the last glacial max — CO2 forcing had about a 2W / m2 increase and ice sheet albedo change amounted to some 25W / m2 less reflected SW..
---- Mayewski, 2016 http://meetingorganizer.copernicus.org/EGU2016/EGU2016-2567.pdf «The demonstration using Greenland ice cores that abrupt shifts in climate, Dansgaard - Oeschger (D - O) events, existed during the last glacial period has had a transformational impact on our understanding of climate change in the naturally forced world.
«Changes in the CO2 and CH4 content have played a significant part in the glacial - interglacial climate changes by amplifying, together with the growth and decay of the Northern Hemisphere ice sheets, the relatively weak orbital forcing»
And study authors found that 2 C to 5 C warming of local ocean waters with somewhat greater local air temperature increases was capable of flooding these basins in stages — forcing Totten's glacial ice to flow out into the Southern Ocean and provide significant contributions to sea level rise.
Overall, when taking a look at these newly realized ice - sheet weaknesses, it's worth noting that the total heat forcing impacting the world's ocean, air, and glacial systems is now rising into a range that is much more in line with Middle Miocene values.
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».
The reason why I think it's wrong is that in her calculation of ESS she takes the radiative forcing caused by albedo changes (resulting from the massive change in ice coverage between a glacial and interglacial state) and assumes it to be a feedback on the CO2 induced temperature - change.
Re # 5 As far as I understand it (drawing on my recollections of a lecture Hansen gave here at Yale a few weeks back), the actual net forcing associated with Milankovich cycles is relatively small, but it tends to trigger massive feedbacks (e.g. polar ice expanding, lowering albedo, cooling, expanding more) that «snowball» into a glacial period.
Because all 2013 Intergovernmental Panel on Climate Change scenarios — except Representative Concentration Pathway 2.6 (RCP2.6), which leads to the total radiative forcing of greenhouse gases of 2.6 W m − 2 in 2100 — imply that cumulative carbon emission will exceed 1,000 Gt in the twenty - first century, our results suggest that anthropogenic interference will make the initiation of the next ice age impossible over a time period comparable to the duration of previous glacial cycles.»
According to Petit et al. [2] the same sequence of events in each glacial termination involved «orbital forcing (with a possible contribution of local insolation changes) followed by two strong amplifiers, greenhouse gases acting first, then deglaciation and ice - albedo feedback».
The orbital forcings of the glacial interglacials were small but amplified by ice albedo feedbacks and GHG feedbacks and I believe the models can come close to approximating most aspects of those cycles.
In some sense, the search for a theory of glacial - interglacial cycles amounts to a search for the «rectifier» which turns the modulation of the amplitude of the seasonal forcing into a rectified signal in global ice volume.
Another way of saying this is to estimate ECS from the last glacial - interglacial transition, the albedo change due to ice sheet melting is taken as a forcing rather than as a feedback.