Hi Stephen, Thanks for this paper with an interesting theory about the 100,000 year cycles. Generally speaking the warming in periods of de-glaciation is more rapid than the cooling during glaciation, so you get a saw-tooth curve, both for the 100,000 year cycle and sub-cycles within it. I hadn't considered that the increased ablation as ice sheet surface thins would provide a dominant feedback effect to speed the warming. During the warming since the last glacial maximum, about 20,000 years ago, there have been several large melt-water pulses, which have choked off the warming. I think what has been happening has been a cycle of Gulf Stream warming, sea ice retreat, warming Arctic, melt-water entering the NW Atlantic nudging the transatlantic currents further southwards allowing the sea ice to advance. (This cause the beginning of the Younger Dryas.) Then the Gulf Stream has warmed a bit more and the cycle repeats.
Into this cycle is an effect of the AMOC (Atlantic Meridian Overturning Circulation), which provides some negative feedback to slow the sea ice albedo feedback warming. Occasionally the AMOC may be switched off almost completely, as happened at the beginning of the Younger Dryas, I believe. So I don't think one does not need the increased ablation effect to explain the temperature trajectory of the past 20,000 years. But I'd appreciate other people's comments. Cheers, John On Thu, Aug 8, 2013 at 5:11 PM, Stephen Salter <s.sal...@ed.ac.uk> wrote: > Hi All > > The site > > http://www.nature.com/nature/**journal/v500/n7461/full/** > nature12374.html?WT.ec_id=**NATURE-20130808<http://www.nature.com/nature/journal/v500/n7461/full/nature12374.html?WT.ec_id=NATURE-20130808> > > has an interesting paper about cycles of ices ages. There are different > equilibrium states. > > Stephen > -- > Emeritus Professor of Engineering Design School of Engineering University > of Edinburgh Mayfield Road Edinburgh EH9 3JL Scotland s.sal...@ed.ac.ukTel +44 > (0)131 650 5704 Cell 07795 203 195 WWW.see.ed.ac.uk/~shs > > The University of Edinburgh is a charitable body, registered in > Scotland, with registration number SC005336. > > -- > You received this message because you are subscribed to the Google Groups > "AMEG" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to > arcticmethane+unsubscribe@**googlegroups.com<arcticmethane%2bunsubscr...@googlegroups.com> > . > For more options, visit > https://groups.google.com/**groups/opt_out<https://groups.google.com/groups/opt_out> > . > > > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to geoengineering+unsubscr...@googlegroups.com. To post to this group, send email to geoengineering@googlegroups.com. Visit this group at http://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/groups/opt_out.
