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

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doi: 10.5194/cp-13-249-2017
Author(s): Peyron, Odile; Combourieu-Nebout, Nathalie; Brayshaw, David; Goring, Simon; Andrieu-Ponel, Valérie; Desprat, Stéphanie; Fletcher, Will; Gambin, Belinda; Ioakim, Chryssanthi; Joannin, Sébastien; Kotthoff, Ulrich; Kouli, Katerina; Montade, Vincent; Pross, Jörg; Sadori, Laura; Magny, Michel
Author Affiliation(s): Primary:
Université de Montpellier, Institut des Sciences de l'Evolution, Montpellier, France
Other:
Institut de Paléontologie Humaine, France
University of Reading, United Kingdom
University of Wisconsin at Madison, United States
Aix Marseille Université, France
Université de Recherche Paris Sciences et Lettres, France
University of Manchester, United Kingdom
University of Malta, Malta
Institute of Geology and Mineral Exploration, Greece
Hamburg University, Germany
National and Kapodistrian University of Athens, Greece
Heidelberg University, Germany
Universita di Roma "La Sapienza", Italy
Université de Franche-Comté, France
Volume Title: Climate of the Past
Source: Climate of the Past, 13(3), p.249-265. Publisher: Copernicus, Katlenburg-Lindau, International. ISSN: 1814-9324
Note: In English. 102 refs.; illus., incl. 1 table
Summary: 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 (∼ 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 inferred 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 information, 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° 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 remained above modern values, even during the late-Holocene interval. In contrast, winter precipitation signals are less spatially coherent during the early Holocene but low precipitation 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 precipitation 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 anticyclonic 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.
Year of Publication: 2017
Research Program: ODP Ocean Drilling Program
Key Words: 24 Surficial Geology, Quaternary Geology; Adriatic Sea; Alboran Sea; Annual variations; Atmospheric precipitation; Cenozoic; Climate; Climate change; Cores; Data; Drought; East Mediterranean; Europe; Greece; HadAM3; HadRM3; Holocene; Italy; Leg 161; Lower Holocene; Malta; Marine environment; Mediterranean Sea; Mediterranean region; Metadata; Middle Holocene; Miospores; Model-data comparison; Models; Moisture; ODP Site 976; Ocean Drilling Program; Paleoclimatology; Palynomorphs; Patterns; Pollen; Pollen analysis; Quaternary; Reconstruction; Regional; Scale models; Seasonal variations; Sicily Italy; Signals; Simulation; Southern Europe; Spatial distribution; Spatial variations; Statistical analysis; Strait of Sicily; Temporal distribution; Terrestrial environment; Upper Holocene; West Mediterranean
Coordinates: N400000 N450000 E0150000 E0100000
N361219 N361219 W0041845 W0041845
N350000 N400000 E0200000 E0150000
Record ID: 2017050128
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Copernicus Gesellschaft, Katlenburg-Lindau, Germany