Dependence of Eemian Greenland temperature reconstructions on the ice sheet topography

Merz, Niklaus; Born, Andreas; Raible, Christoph; Fischer, Hubertus; Stocker, Thomas (2014). Dependence of Eemian Greenland temperature reconstructions on the ice sheet topography. Climate of the past, 10(3), pp. 1221-1238. Copernicus Publications 10.5194/cp-10-1221-2014

[img]
Preview
Text
cp-10-1221-2014.pdf - Published Version
Available under License Creative Commons: Attribution (CC-BY).

Download (3MB) | Preview

The influence of a reduced Greenland Ice Sheet (GrIS) on Greenland's surface climate during the Eemian interglacial is studied using a set of simulations with different GrIS realizations performed with a comprehensive climate model. We find a distinct impact of changes in the GrIS topography on Greenland's surface air temperatures (SAT) even when correcting for changes in surface elevation, which influences SAT through the lapse rate effect. The resulting lapse-rate-corrected SAT anomalies are thermodynamically driven by changes in the local surface energy balance rather than dynamically caused through anomalous advection of warm/cold air masses. The large-scale circulation is indeed very stable among all sensitivity experiments and the Northern Hemisphere (NH) flow pattern does not depend on Greenland's topography in the Eemian. In contrast, Greenland's surface energy balance is clearly influenced by changes in the GrIS topography and this impact is seasonally diverse. In winter, the variable reacting strongest to changes in the topography is the sensible heat flux (SHF). The reason is its dependence on surface winds, which themselves are controlled to a large extent by the shape of the GrIS. Hence, regions where a receding GrIS causes higher surface wind velocities also experience anomalous warming through SHF. Vice-versa, regions that become flat and ice-free are characterized by low wind speeds, low SHF, and anomalous low winter temperatures. In summer, we find surface warming induced by a decrease in surface albedo in deglaciated areas and regions which experience surface melting. The Eemian temperature records derived from Greenland proxies, thus, likely include a temperature signal arising from changes in the GrIS topography. For the Eemian ice found in the NEEM core, our model suggests that up to 3.1 °C of the annual mean Eemian warming can be attributed to these topography-related processes and hence is not necessarily linked to large-scale climate variations.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Climate and Environmental Physics
10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR)

UniBE Contributor:

Merz, Niklaus; Born, Andreas; Raible, Christoph; Fischer, Hubertus and Stocker, Thomas

Subjects:

500 Science > 530 Physics
500 Science > 550 Earth sciences & geology

ISSN:

1814-9324

Publisher:

Copernicus Publications

Language:

English

Submitter:

Doris Rätz

Date Deposited:

18 Aug 2014 15:12

Last Modified:

13 Jul 2015 14:57

Publisher DOI:

10.5194/cp-10-1221-2014

BORIS DOI:

10.7892/boris.54295

URI:

https://boris.unibe.ch/id/eprint/54295

Actions (login required)

Edit item Edit item
Provide Feedback