 |
| Titel |
On the effect of orbital forcing on mid-Pliocene climate, vegetation and ice sheets |
| VerfasserIn |
M. Willeit, A. Ganopolski, G. Feulner |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1814-9324
|
| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 9, no. 4 ; Nr. 9, no. 4 (2013-08-01), S.1749-1759 |
| Datensatznummer |
250018104
|
| Publikation (Nr.) |
 copernicus.org/cp-9-1749-2013.pdf |
|
|
|
|
|
| Zusammenfassung |
We present results from modelling of the mid-Pliocene warm period (3.3–3
million years ago) using the Earth system model of intermediate complexity
CLIMBER-2 analysing the effect of changes in boundary conditions as well as
of orbital forcing on climate.
First we performed equilibrium experiments following the PlioMIP
(Pliocene Model Intercomparison Project) protocol with a CO2
concentration of 405 ppm, reconstructed mid-Pliocene
orography and vegetation and a present-day orbital configuration. Simulated
global Pliocene warming is about 2.5 °C, fully consistent with
results of atmosphere–ocean general circulation model simulations performed
for the same modelling setup. A factor separation analysis attributes
1.5 °C warming to CO2, 0.3 °C to orography,
0.2 °C to ice sheets and 0.4 °C to vegetation.
Transient simulations for the entire mid-Pliocene warm period with
time-dependent orbital forcing as well as interactive ice sheets and
vegetation give a global warming varying within the range
1.9–2.8 °C. Ice sheet and vegetation feedbacks in synergy act as
amplifiers of the orbital forcing, transforming seasonal insolation
variations into an annual mean temperature signal. The effect of orbital
forcing is more significant at high latitudes, especially during boreal
summer, when the warming over land varies in the wide range from
0 to 10 °C. The modelled ice-sheet extent and vegetation distribution
also show significant temporal variations. Modelled and reconstructed data
for Northern Hemisphere sea-surface temperatures and vegetation distribution
show the best agreement if the reconstructions are assumed to be
representative for the warmest periods during the orbital cycles. This
suggests that low-resolution Pliocene palaeoclimate reconstructions can
reflect not only the impact of increased CO2 concentrations and
topography changes but also the effect of orbital forcing. Therefore, the
climate (Earth system) sensitivity estimates from Pliocene reconstructions
which do not account for the effect of orbital forcing can be biased toward
high values. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|