*Hi everybody,* Why has no one mentioned one possible causes of the melting/sliding of the major and thick Greenland's ice sheet could be due to the minute temperature changes (primarily, warming up) of the earth/ground beneath ? Or have I missed out on this ?
Comments and advices, please ! *Raymond Law * On Tue, Nov 17, 2009 at 7:04 PM, John Nissen <[email protected]> wrote: > > Hi all, > > Professor Mike Hulme gave a talk at the RGS yesterday evening [1], in which > the Greenland ice sheet was shown as a tipping point, along with a dozen > others on a map of the world [2]. > > The BBC article below shows how positive feedbacks are building up in the > Arctic. What is not discussed is whether the whole sections of ice sheet > could become unstable and slip off into the sea, causing a massive step > change in sea level, as shown to have happened from time to time in the > geological record of the Ice Ages [3]. If we are to avoid a complete > tipping of this system, sooner or later giving us 7 metres of sea level > rise, there seems to be no alternative to geoengineering to cool the > Arctic. And the sooner we start the geoengineering, the more likely we are > to succeed in halting the tipping process. > > From http://news.bbc.co.uk/1/hi/sci/tech/8357537.stm > > --- > > *The Greenland ice sheet is losing its mass faster than in previous years > and making an increasing contribution to sea level rise, a study has > confirmed.* > > Published in the journal Science, it has also given scientists a clearer > view of why the sheet is shrinking. > > The team used weather data, satellite readings and models of ice sheet > behaviour to analyse the annual loss of 273 thousand million tonnes of ice. > > Melting of the entire sheet would raise sea levels globally by about 7m > (20ft). > > For the period 2000-2008, melting Greenland ice raised sea levels by an > average of about 0.46mm per year. > *If you multiply these numbers up it puts us well beyond the IPCC > estimates for 2100* > Professor Roger Barry > > Since 2006, that has increased to 0.75mm per year. > > "Since 2000, there's clearly been an accelerating loss of mass [from the > ice sheet]," said lead researcher Michiel van den Broeke from Utrecht > University in the Netherlands. > > "But we've had three very warm summers, and that's enhanced the melt > considerably. > > "If this is going to continue, I cannot tell - but we do of course expect > the climate to become warmer in the future." > > In total, sea levels are rising by about 3mm per year, principally because > seawater is expanding as it warms. > > *Sea change* > > Changes to the Greenland sheet and its much larger counterpart in > Antarctica are subjects commanding a lot of interest within the scientific > community because of the potential they have to raise sea levels to an > extent that would flood many of the world's major cities. > CLIMATE CHANGE GLOSSARY > Select a term from the dropdown: Glossary Adaptation Annex I countries Annex > II countries Anthropogenic climate change Atmospheric aerosols Bali action > plan Bali roadmap Baseline for cuts Black carbon Boxer-Kerry bill Business > as usual Cap and trade Carbon capture and storage (CCS) Carbon dioxide > (CO2) Carbon dioxide (CO2) equivalent Carbon intensity Carbon leakage Carbon > neutral Carbon offsetting Carbon sequestration Certified Emission > Reduction (CER) Clean Coal Technology Clean Development Mechanism (CDM) > Climate > change CFC CO2 COP15 Dangerous climate change Deforestation Emission > Trading Scheme (ETS) EU Burden-sharing agreement Fossil_fuels Geological > sequestration Global average temperature Global energy budget Global > dimming Global warming Greenhouse gases (GHGs) Greenhouse effect IPCC Joint > implementation Kyoto Protocol Major Economies Forum on Energy and Climate > Methane Mitigation Natural greenhouse effect Non-annex I countries Per-capita > emissions Pre-industrial levels of carbon dioxide REDD Stern review Technology > transfer UNFCCC Waxman-Markey energy bill Weather > > Climate change - A pattern of change affecting global or regional climate > as measured by yardsticks such as average temperature and rainfall, or an > alteration in frequency of extreme weather conditions. This variation may be > caused by both natural processes and human activity. > > Global warming is one aspect of climate change. > Suggest additions <http://news.bbc.co.uk/1/hi/sci/tech/8329823.stm> > Glossary in full <http://news.bbc.co.uk/1/hi/sci/tech/8314171.stm> > > The 2007 Intergovernmental Panel on Climate Change (IPCC) report projected > a sea level rise of 28-43cm during this century. > > But it acknowledged this was almost certainly an underestimate because > understanding of how ice behaves was not good enough to make reliable > projections. > > By combining different sources of data in the way it has, and by > quantifying the causes of mass loss, the new study has taken a big step > forwards, according to Roger Barry, director of the World Data Center for > Glaciology at the University of Colorado in Boulder, US. > > "I think it's a very significant paper; the results in it are certainly > very significant and new," he said. > > "It does show that the [ice loss] trend has accelerated, and the reported > contribution to sea level rise also shows a significant acceleration - so if > you multiply these numbers up it puts us well beyond the IPCC estimates for > 2100." > > Professor Barry was an editor on the section of the IPCC report dealing > with the polar regions. > > *On reflection* > > An ice sheet can lose mass because of increased melting on the surface, > because glaciers flow more quickly into the ocean, or because there is less > precipitation in the winter so less bulk is added inland. > > The new research shows that in Greenland, about half the loss comes from > faster flow to the oceans, and the other half from changes on the ice sheet > itself - principally surface melting. > [image: Artist's impression of Grace satellite in orbit] > The Grace satellites provide a twin eye on gravity at the Earth's surface > > Another analysis of satellite data, published in September, showed that of > 111 fast-moving Greenland glaciers studied, 81 were thinning at twice the > rate of the slow-moving ice beside them. > > This indicates that the glaciers are accelerating and taking more ice into > the surrounding sea. > > Melting on the ice sheet's surface acts as a feedback mechanism, Dr van den > Broeke explained, because the liquid water absorbs more and reflects less of > the incoming solar radiation - resulting in a heating of the ice. > > "Over the last 10 years, it's quite simple; warming over Greenland has > caused the melting to increase, and that's set off this albedo feedback > process," he told BBC News. > > "Quite likely the oceans have also warmed, and it's likely that explains > the [acceleration of] outlet glaciers because they're warmed from below." > > Data provided over just the last few years by the Grace satellite mission - > used in this study - is giving researchers a closer view of regional > variations across the territory. > > Grace's twin satellites map gravity at the Earth's surface in unprecedented > detail; and it is now possible to tease out from the data that most of the > mass is being lost in the southeast, southwest and northwest at low > elevations where the air will generally be warmer than at high altitudes. > > Professor Barry cautioned that the Grace mission, which has produced > valuable data about Antarctica as well as Greenland, has only a further two > years to run, and that no replacement is currently scheduled. > > --- > > For graphic illustration of what we're facing, I can recommend James > Balog's time-lapse photography: > > http://www.ted.com/talks/james_balog_time_lapse_proof_of_extreme_ice_loss.html > > Cheers from Chiswick, > > John > > [1] RGS lectures > http://www.rgs.org/WhatsOn/London+Lectures/Monday+night+Lectures.htm > > [2] Tipping points map > http://web.me.com/stewartbrand/DISCIPLINE_footnotes/Tipping_points.html > > [3] Hansen on scientific reticence and sea level rise > http://www.iop.org/EJ/article/1748-9326/2/2/024002/erl7_2_024002.html > > -- > You received this message because you are subscribed to the Google Groups > "geoengineering" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]<geoengineering%[email protected]> > . > For more options, visit this group at > http://groups.google.com/group/geoengineering?hl=. > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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