Quantitatively, I have no idea how long it would be, and my guess is that the apparent oscillation in the extent of sea ice is not being driven by this mechanism but by an oscillation somewhere else. But anyway, it takes time for ice on Greenland to melt, then it takes time for the meltwater to flow, then it takes time for additional sea ice to form (I expect most of the melting of Greenland would be in the summer, and most of the resulting increase in sea ice would be in the winter), and then it takes some time for the region to cool. I don't know whether the melting of Greenland would mostly be in-situ, or whether it would mostly result from the ice flowing faster when it's warmer; in the latter case, it takes time for the ice to warm up and flow. On the upswing of temperature, it takes time for the less-salty water to mix or to become saltier by evaporation.
On Feb 8, 4:25 pm, "John Nissen" <[email protected]> wrote: > Hi dsw_s, > > There could be an oscillation, but your mechanism would not explain the four > year delay. Perhaps the delay in negative feedback, which would produce > such an oscillation, is due to the time for meltwater to flow from West > Greenland, through the David Strait [1], into the West Atlantic and nudge > the Gulf Stream a little southwards, thereby allowing a temporary increase > in the formation of sea ice. > > BTW, there is a theory that a massive meltwater pulse could have initiated > the rapid cooling at the start of the Younger Dryas, through the above > mechanism. > > However this oscillation, if it is an oscillation, could be coming to an > end, with the growing positive feedback overwhelming any negative feedback > effects. Then we could find the retreat of Arctic sea ice unstoppable, even > with SRM geoengineering. We'd be past the dreaded point of no return. > > Cheers from Chiswick, > > John > > [1] Seehttp://visibleearth.nasa.gov/view_rec.php?id=3240 > > ----- Original Message ----- > From: "dsw_s" <[email protected]> > To: "geoengineering" <[email protected]> > Sent: Saturday, February 07, 2009 1:49 PM > Subject: [geo] Re: The warming Arctic - a global crisis > > The figure athttp://nsidc.org/arcticseaicenews/looks like an > oscillation with a period of about four years, superimposed on a > downward trend. I had just been thinking of one thing that could > cause such an oscillation: When the arctic is warmer, more of > Greenland melts When more of Greenland melts, the arctic ocean is > less salty and more stratified. When the ocean is more stratified and > less salty, there's a temporary increase in the formation of sea ice. > Then there's the effect of arctic temperature and evaporation rate on > continental weather, including snow cover. The point is still that it > takes more than simple-and-obvious to sort it out. > > On Feb 7, 5:59 am, Stephen Salter <[email protected]> wrote: > > Hi All > > > There is more on February 09 ice at > > >http://nsidc.org/arcticseaicenews/ > > > Stephen > > > Emeritus Professor of Engineering Design > > School of Engineering and Electronics > > University of Edinburgh > > Mayfield Road > > Edinburgh EH9 3JL > > Scotland > > tel +44 131 650 5704 > > fax +44 131 650 5702 > > Mobile 07795 203 195 > > [email protected]http://www.see.ed.ac.uk/~shs > > > John Nissen wrote: > > > Talk about unpleasant surprises (see my previous posting below), look at > > > this: > > > > 'Warm everywhere' in Arctic this winter > > > > While parts of North America have been in the icy grips of an unusually > > > cold > > > and snowy winter recently, the Arctic has been downright balmy compared > > > to > > > past winters. > > > >http://www.msnbc.msn.com/id/29038734/from/ET/ > > > > (with thanks to Albert Kallio for finding this) > > > ---- > > > > 'Warm everywhere' in Arctic this winter > > > Expert: Dec.-Jan. temps drop, both are 'crucial ice-growing months' > > > > By Andrea Thompson > > > updated 5:13 p.m. ET Feb. 5, 2009 > > > While parts of North America have been in the icy grips of an unusually > > > cold > > > and snowy winter recently, the Arctic has been downright balmy compared > > > to > > > past winters. > > > > These warmer-than-normal temperatures mean that the sea ice in the > > > Arctic is > > > looking pretty anemic, despite the winter season. > > > > Arctic ice goes through a normal cycle of summer thaw and winter > > > re-freeze. > > > In recent decades, however, sea ice has become overall less extensive > > > and > > > thinner, leading to forecasts that in future decades the polar region > > > will > > > be ice-free during summer. The trend looks to be continuing this winter, > > > scientists now say. > > --~--~---------~--~----~------------~-------~--~----~ 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] For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en -~----------~----~----~----~------~----~------~--~---
