We've updated our Privacy Policy to make it clearer how we use your personal data. We use cookies to provide you with a better experience. You can read our Cookie Policy here.


New Climate Model Explains Ice-Age Variability

Sea ice in the arctic ocean.
Credit: MARUM – Center for Marine Environmental Sciences, University of Bremen; V. Diekamp.
Listen with
Register for free to listen to this article
Thank you. Listen to this article using the player above.

Want to listen to this article for FREE?

Complete the form below to unlock access to ALL audio articles.

Read time: 2 minutes

Dur­ing the last ice age, the last gla­cial max­imum about 20,000 years ago, the cli­mate in the North At­lantic un­der­went much greater multi-centen­nial vari­ab­il­ity than it does in the present warm period. This is sup­por­ted by evid­ence found in ice and sea­floor cores. Re­search­ers at MARUM – Cen­ter for Mar­ine En­vir­on­mental Sci­ences and the De­part­ment of Geosciences at the Uni­versity of Bre­men, and at the Vrije Uni­versiteit Am­s­ter­dam (The Neth­er­lands) have now shown for the first time, based on a cli­mate model, that in­ternal mech­an­isms such as tem­per­at­ure and sa­lin­ity dis­tri­bu­tion in the ocean are driv­ing this multi-centen­nial vari­ab­il­ity. Their res­ults are now pub­lished in the journal Science Advances.

The cyc­lic pro­cess is self-sus­tained, as the weak­en­ing of the AMOC res­ults in less low-sa­lin­ity wa­ter be­ing trans­por­ted north­ward again from the South At­lantic. Con­sequently, sa­lin­ity in the North At­lantic may in­crease again, res­ult­ing in the pro­duc­tion of more deep wa­ter. As Mat­thias Prange ex­plains, “These pro­cesses in­dic­ate that the multi-centen­nial cli­mate vari­ab­il­ity is closely re­lated to dif­fer­ences in the sa­lin­ity and tem­per­at­ure in the wa­ter column.” And al­though the amp­litudes of the vari­ation are low, there are clear ef­fects on the ex­tent of North At­lantic sea ice and on the tem­per­at­ures in Green­land. “The av­er­age an­nual tem­per­at­ures there vary by about four de­grees Celsius as a res­ult of the AMOC os­cil­la­tions,” con­cludes Prange.

High-resolution paleodata

In or­der to sup­port these find­ings of the mod­els, the sci­ent­ists in­vest­ig­ated the sea-sur­face tem­per­at­ures for that time period. “To do this, we com­piled and ana­lyzed all of the high-res­ol­u­tion re­con­struc­tions from mar­ine sed­i­ments of the North At­lantic," says Dr. Lu­kas Jonkers, co-au­thor of the study and mi­cro­pa­le­on­to­lo­gist at MARUM. “High-res­ol­u­tion here means that the data points of a series av­er­age no more than 200 years apart, with no single step greater than 1000 years.” The pa­leoarchives stud­ied provide evid­ence for re­cur­ring tem­per­at­ure os­cil­la­tions in the sur­face wa­ters every 150 to 1000 years dur­ing the last gla­cial max­imum, which is con­sist­ent with the mod­elled multi-centen­nial cli­mate vari­ab­il­ity with in­ternal for­cing mech­an­isms.

Want more breaking news?

Subscribe to Technology Networks’ daily newsletter, delivering breaking science news straight to your inbox every day.

Subscribe for FREE

The importance of understanding feedback processes

Re­cent re­search find­ings un­der­score the im­port­ance of de­tailed study and un­der­stand­ing of feed­back pro­cesses in the cli­mate sys­tem. Mat­thias Prange em­phas­izes the need for a deeper un­der­stand­ing of cli­mate vari­ab­il­ity at vari­ous time scales, as this could have rami­fic­a­tions for fu­ture cli­mate change that could lead to un­ex­pec­ted and un­desir­able sur­prises for so­ci­et­ies. These find­ings are also in­cor­por­ated into the work of the Cluster of Ex­cel­lence "The Ocean Floor – Earth’s Un­charted In­ter­face", which is based at MARUM.

Reference: Prange M, Jonkers L, Merkel U, Schulz M, Bakker P. A multicentennial mode of North Atlantic climate variability throughout the Last Glacial Maximum. Sci Adv. 2023;9(44):eadh1106. doi: 10.1126/sciadv.adh1106

This article has been republished from the following materials. Note: material may have been edited for length and content. For further information, please contact the cited source.