The ends of the last two ice ages were very unlike , and now paleoclimatologists think they realise why . The finding reward how the same global average temperature can develop giving remainder in regional temperatures , which in turn can touch how much ocean point rise .
“ Ice - age cycles may superficially look similar to one another,”saidDr . Gianluca Marino of the Australian National University . “ But there are of import difference in the relationship between thaw of continental ice sheets and world climate variety . ”
When the meth age before last finish 135,000 - 128,000 years ago , ocean levels rose even more dramatically than when the last one ended 20,000 - 10,000 years ago . “ We knew the ocean level had overshoot its present levels during the last interglacial catamenia , but did not know why , ” Marino said .
The reason , Marinoreveals inNature , lies in the sea currents that distribute rut around the major planet . The 2nd - to - last crank long time saw , “ A dramatic crash of the Northern Hemisphere chalk flat solid into the North Atlantic Ocean [ that ] suppress the ocean circulation and cause chilling in the North Atlantic , ” fit in to conscientious objector - author Professor Eelco Rohling .
Some people havebecome excited byreports that a weakening of the Gulf Stream may lead toa cool North Atlantic , suppose it will counterbalance ball-shaped thaw . However , such changes may cause a redistribution of heating , rather than make it go off .
When the second - to - last sparkler old age terminate , the suppression of Atlantic control surface currents go away the Southern Ocean even warm than it would otherwise have been . Rohling explained that this , “ Destabilized Antarctic kingdom icing , causing a sequel of melting that eventually drive ocean level rise to several metre above the present level . ”
The author attain these conclusions by reckon the timing of events at the end of the penultimate methamphetamine age more precisely than before . By linking nautical records obtained from ocean drilling at two point in the Mediterranean with incisively dated cave records , they were able-bodied to establish in item when changes in climate and sea levels occurred , Marino assure IFLScience . “ We were able-bodied to establish a vulgar chronology from all important climate parameters , orbicular ocean point , North Atlantic and Antarctic temperature , and powerful nursery gases like carbon paper dioxide and methane . ”
Stalactites and stalagmite like these from Soreq Cave in Israel preserve a disk of local climatical conditions at the time they formed . Credit : Eelco Rohling . When warming of the Southern Ocean occurred 135,000 years ago , the Earth was experiencing a sharper raise in Northern Hemisphere solar radiotherapy than at the destruction of the last water ice eld , Marino state . This caused the dramatic collapse of the Northern Hemisphere ice sail and climate change across the planet . When the Earth emerged from the last meth age , however , speedy northern Methedrine collapse and climate change happen at different times , which produced less thawing in Antarctica and prevented ocean level from arise as much as the previous fourth dimension .
Marino aver the work does not provide a direct indication of the future tense of ice sheets as humans warm the world , since circumstances are now so unlike , with warm find faster to much smaller glass canvass . Nevertheless , he pronounce , “ Understanding how climate and sea level changed in the past can learn us much about the sensitiveness of methamphetamine hydrochloride bed sheet to clime change . ”
