The relative contribution of orbital forcing and greenhouse gases to the North American deglaciation. Issue 22 (19th November 2015)

• Record Type: Journal Article
• Authors: Gregoire, Lauren J.; Valdes, Paul J.; Payne, Antony J.
• Is Part Of: Geophysical research letters. Volume 42:Issue 22(2015:Nov.)
• Page Start: 9970
• Page End: 9979
• Publication Date: 2015-11-19
• Subjects: deglaciation -- ice sheets -- North America -- orbit -- greenhouse gases -- Milankovic; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2015GL066005
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Understanding what drove Northern Hemisphere ice sheet melt during the last deglaciation (21–7 ka) can help constrain how sensitive contemporary ice sheets are to greenhouse gas (GHGs) changes. The roles of orbital forcing and GHGs in the deglaciation have previously been modeled but not yet quantified. Here for the first time we calculate the relative effect of these forcings on the North American deglaciation by driving a dynamical ice sheet model (GLIMMER‐CISM) with a set of unaccelerated transient deglacial simulations with a full primitive equation‐based ocean‐atmosphere general circulation model (FAMOUS). We find that by 9 ka, orbital forcing has caused 50% of the deglaciation, GHG 30%, and the interaction between the two 20%. Orbital forcing starts affecting the ice volume at 19 ka, 2000 years before CO2 starts increasing in our experiments, a delay which partly controls their relative effect. Key Points: We decompose the forcings of North American ice volume changes during the last deglaciation Orbital forcing drives 50%, greenhouse gases 30%, and forcing interactions 20% of the deglaciation The difference in timing of the forcings partly explains their relative contribution