Precipitation changes in the Mediterranean basin during the Holocene from terrestrial and marine pollen records: a model-data comparison

Type Article
Date 2017-03-24
Language English
Author(s) Peyron Odile1, Combourieu-Nebout Nathalie2, Brayshaw David3, Goring Simon4, Andrieu-Ponel Valerie5, Desprat Stephanie6, 7, Fletcher Will8, Gambin Belinda9, Ioakim Chryssanthi10, Joannin SebastienORCID1, Kotthoff Ulrich11, 12, Kouli KaterinaORCID13, Montade Vincent1, Pross Jörg14, Sadori LauraORCID15, Magny Michel16
Affiliation(s) 1 : Univ Montpellier, Inst Sci Evolut ISEM, Montpellier, France.
2 : MNHN, Inst Paleontol Humaine, UMR 7194, Paris, France.
3 : Univ Reading, Dept Meteorol, Reading, Berks, England.
4 : Univ Wisconsin, Dept Geog, Madison, WI 53706 USA.
5 : Aix Marseille Univ, Inst Mediterraneen Biodivers & Ecol Marine & Cont, Aix En Provence, France.
6 : PSL Res Univ, EPHE, Lab Paleoclimatol & Paleoenvironm Marins, Pessac, France.
7 : Univ Bordeaux, EPOC, UMR5805, Pessac, France.
8 : Univ Manchester, Sch Environm Educ & Dev, Geog, Manchester, Lancs, England.
9 : Univ Malta, Inst Earth Syst, Msida, Malta.
10 : Inst Geol & Mineral Explorat, Athens, Greece.
11 : Univ Hamburg, Ctr Nat Hist, Hamburg, Germany.
12 : Univ Hamburg, Inst Geol, Hamburg, Germany.
13 : Univ Athens, Dept Geol & Geoenvironm, Athens, Greece.
14 : Heidelberg Univ, Inst Earth Sci, Paleoenvironm Dynam Grp, Heidelberg, Germany.
15 : Univ Roma La Sapienza, Dipartimento Biol Ambientale, Rome, Italy.
16 : Univ Franche Comte, Chronoenvironm UMR6249, Besancon, France.
Source Climate Of The Past (1814-9324) (Copernicus Gesellschaft Mbh), 2017-03-24 , Vol. 13 , N. 3 , P. 249-265
DOI 10.5194/cp-13-249-2017
WOS© Times Cited 54
Note Special issues Human–land–sea interactions in the Mediterranean Basin: a Holocene perspective Editor(s): M.-A. Sicre, J. Guiot, L. Carozza, N. Combourieu Nebout, B. Martrat, and M.-F. Loutre
Abstract

Climate evolution of the Mediterranean region during the Holocene exhibits strong spatial and temporal variability, which is notoriously difficult for models to reproduce. We propose here a new proxy-based climate synthesis synthesis and its comparison -at a regional (similar to 100 km) level - with a regional climate model to examine (i) opposing northern and southern precipitation regimes and (ii) an east-to-west precipitation dipole during the Holocene across the Mediterranean basin. Using precipitation estimates in-ferred from marine and terrestrial pollen archives, we focus on the early to mid-Holocene (8000 to 6000 cal yr BP) and the late Holocene (4000 to 2000 cal yr BP), to test these hypotheses on a Mediterranean-wide scale. Special attention was given to the reconstruction of season-specific climate in-formation, notably summer and winter precipitation. The reconstructed climatic trends corroborate the north-south partition of precipitation regimes during the Holocene. During the early Holocene, relatively wet conditions occurred in the south-central and eastern Mediterranean regions, while drier conditions prevailed from 45 degrees N northwards. These patterns then reverse during the late Holocene. With regard to the existence of a west-east precipitation dipole during the Holocene, our results show that the strength of this dipole is strongly linked to the reconstructed seasonal parameter; early-Holocene summers show a clear east-west division, with summer precipitation having been highest in Greece and the eastern Mediterranean and lowest over Italy and the western Mediterranean. Summer precipitation in the east re-mained above modern values, even during the late-Holocene interval. In contrast, winter precipitation signals are less spatially coherent during the early Holocene but low precipita-tion is evidenced during the late Holocene. A general drying trend occurred from the early to late Holocene, particularly in the central and eastern Mediterranean. For the same time intervals, pollen-inferred precipita-tion estimates were compared with model outputs, based on a regional-scale downscaling (HadRM3) of a set of global climate-model simulations (HadAM3). The high-resolution detail achieved through the downscaling is intended to enable a better comparison between site-based paleo-reconstructions and gridded model data in the complex terrain of the Mediterranean; the model outputs and pollen-inferred precipitation estimates show some overall correspondence, though modeled changes are small and at the absolute margins of statistical significance. There are suggestions that the eastern Mediterranean experienced wetter summer conditions than present during the early and late Holocene; the drying trend in winter from the early to the late Holocene also appears to be simulated. The use of this high-resolution regional climate model highlights how the inherently patchy nature of climate signals and paleo-records in the Mediterranean basin may lead to local signals that are much stronger than the large-scale pattern would suggest. Nevertheless, the east-to-west division in summer precipitation seems more marked in the pollen reconstruction than in the model outputs. The footprint of the anomalies (like today, or dry winters and wet summers) has some similarities to modern analogue atmospheric circulation patterns associated with a strong westerly circulation in winter (positive Arctic Oscillation-North Atlantic Oscillation (AO-NAO)) and a weak westerly circulation in summer associated with anticy-clonic blocking; however, there also remain important differences between the paleo-simulations and these analogues. The regional climate model, consistent with other global models, does not suggest an extension of the African summer monsoon into the Mediterranean. Therefore, the extent to which summer monsoonal precipitation may have existed in the southern and eastern Mediterranean during the mid-Holocene remains an outstanding question.

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Peyron Odile, Combourieu-Nebout Nathalie, Brayshaw David, Goring Simon, Andrieu-Ponel Valerie, Desprat Stephanie, Fletcher Will, Gambin Belinda, Ioakim Chryssanthi, Joannin Sebastien, Kotthoff Ulrich, Kouli Katerina, Montade Vincent, Pross Jörg, Sadori Laura, Magny Michel (2017). Precipitation changes in the Mediterranean basin during the Holocene from terrestrial and marine pollen records: a model-data comparison. Climate Of The Past, 13(3), 249-265. Publisher's official version : https://doi.org/10.5194/cp-13-249-2017 , Open Access version : https://archimer.ifremer.fr/doc/00420/53173/