scholarly journals Deglacial and Holocene vegetation and climatic changes at the southernmost tip of the Central Mediterranean from a direct land-sea correlation

2012 ◽  
Vol 8 (6) ◽  
pp. 5687-5741 ◽  
Author(s):  
S. Desprat ◽  
N. Combourieu-Nebout ◽  
L. Essallami ◽  
M. A. Sicre ◽  
I. Dormoy ◽  
...  
Keyword(s):  
Late Holocene ◽  
Winter Precipitation ◽  
Climatic Changes ◽  
Last Deglaciation ◽  
Central Mediterranean ◽  
The Holocene ◽  
Southern Central ◽  
The Last Deglaciation ◽  
Trees And Shrubs ◽  
Vegetal Cover

Abstract. Despite a large number of studies, the long-term and millennial to centennial-scale climatic variability in the Mediterranean region during the last deglaciation and the Holocene is still debated, in particular in the Southern Central Mediterranean. In this paper, we present a new marine pollen sequence (MD04-2797CQ) from the Siculo-Tunisian Strait documenting the regional vegetation and climatic changes in the Southern Central Mediterranean during the last deglaciation and the Holocene. The MD04-2797CQ marine pollen sequence shows that semi-desert plants dominated the vegetal cover in the Southern Central Mediterranean between 18 and 12.3 kyr BP indicating prevailing dry conditions during the deglaciation, even during the Greenland Interstadial (GI)-1. Such arid conditions likely restricted the expansion of the trees and shrubs despite the GI-1 climatic amelioration. Across the transition Greenland Stadial (GS)-1 – Holocene, Asteraceae-Poaceae steppe became dominant till 10.1 kyr. This record underlines with no chronological ambiguity that even though temperatures increased, deficiency in moisture availability persisted into the Early Holocene.Temperate trees and shrubs with heaths as oak forest understorey or heath maquis expanded between 10.1 and 6.6 kyr, while Mediterranean plants only developed from 6.6 kyr onwards. These changes in vegetal cover show that the regional climate in Southern Central Mediterranean was wetter during Sapropel 1 (S1) and became drier during the Mid- to Late Holocene. Wetter conditions during S1 were likely due to increased winter precipitation while summers remained dry. We suggest, in agreement with published modelling experiments, that the increased melting of the Laurentide Ice Sheet between 10 to 6.8 kyr in conjunction with weak winter insolation played a major role in the development of winter precipitation maxima in the Mediterranean region in controlling the strength and position of the North Atlantic storm track. Finally, our data provide evidences of centennial-scale vegetation and climatic changes in the Southern Central Mediterranean. During the wet Early Holocene, alkenones-derived cooling episodes are synchronous to herbaceous composition changes that indicate muted changes in precipitation. In contrast, enhanced aridity episodes, as detected by strong reduction in trees and shrubs, are recorded during the Mid- to Late Holocene. We show that the impact of the Holocene cooling events depend on the baseline climate states insolation and ice sheet volume, shaping the response of the mid-latitude atmospheric circulation.

scholarly journals Deglacial and Holocene vegetation and climatic changes in the southern Central Mediterranean from a direct land–sea correlation

2013 ◽  
Vol 9 (2) ◽  
pp. 767-787 ◽  
Author(s):  
S. Desprat ◽  
N. Combourieu-Nebout ◽  
L. Essallami ◽  
M. A. Sicre ◽  
I. Dormoy ◽  
...  
Keyword(s):  
Winter Precipitation ◽  
Climatic Changes ◽  
Early Holocene ◽  
Last Deglaciation ◽  
Central Mediterranean ◽  
The Holocene ◽  
Southern Central ◽  
The Last Deglaciation ◽  
The Mediterranean ◽  
Trees And Shrubs

Abstract. Despite a large number of studies, the long-term and millennial to centennial-scale climatic variability in the Mediterranean region during the last deglaciation and the Holocene is still debated, including in the southern Central Mediterranean. In this paper, we present a new marine pollen sequence (core MD04-2797CQ) from the Siculo-Tunisian Strait documenting the regional vegetation and climatic changes in the southern Central Mediterranean during the last deglaciation and the Holocene. The MD04-2797CQ marine pollen sequence shows that semi-desert plants dominated the vegetal cover in the southern Central Mediterranean between 18.2 and 12.3 ka cal BP, indicating prevailing dry conditions during the deglaciation, even during the Greenland Interstadial (GI)-1. Across the transition Greenland Stadial (GS)-1 – Holocene, Asteraceae-Poaceae steppe became dominant till 10.1 ka cal BP. This record underlines with no chronological ambiguity that even though temperatures increased, deficiency in moisture availability persisted into the early Holocene. Temperate trees and shrubs with heath underbrush or maquis expanded between 10.1 and 6.6 ka, corresponding to Sapropel 1 (S1) interval, while Mediterranean plants only developed from 6.6 ka onwards. These changes in vegetal cover show that the regional climate in southern Central Mediterranean was wetter during S1 and became drier during the mid- to late Holocene. Wetter conditions during S1 were likely due to increased winter precipitation while summers remained dry. We suggest, in agreement with published modeling experiments, that the early Holocene increased melting of the Laurentide Ice Sheet in conjunction with weak winter insolation played a major role in the development of winter precipitation maxima in the Mediterranean region in controlling the strength and position of the North Atlantic storm track. Finally, our data provide evidence for centennial-scale vegetation and climatic changes in the southern Central Mediterranean. During the wet early Holocene, alkenone-derived cooling episodes are synchronous with herbaceous composition changes that indicate muted changes in precipitation. In contrast, enhanced aridity episodes, as detected by strong reduction in trees and shrubs, are recorded during the mid- to late Holocene. We show that the impact of the Holocene cooling events on the Mediterranean hydroclimate depend on baseline climate states, i.e. insolation and ice sheet extent, shaping the response of the mid-latitude atmospheric circulation.

A 45 kyr laminae record from the Dead Sea: Implications for basin erosion and floods recurrence

2020 ◽  
Author(s):  
Nicolas Waldmann ◽  
Yin Lu ◽  
Revital Bookman ◽  
Shmulik Marco
Keyword(s):  
High Frequency ◽  
Lake Level ◽  
Dead Sea ◽  
Last Deglaciation ◽  
The Holocene ◽  
Lamina Thickness ◽  
The Last Deglaciation ◽  
The Dead ◽  
Basin Erosion ◽  
The Last Glacial

<p>Recording and analyzing how climate change impacts flood recurrence, basin erosion, and sedimentation can improve our understanding of these systems. The aragonite-detritus laminae couplets comprising the lacustrine formations that were deposited in the Dead Sea Basin are considered as faithful monitors of the freshwater supply to the lakes. We count a total of ~5600 laminae couplets deposited in the last 45 kyr (MIS3-MIS1) at the Dead Sea depocenter, which encompass the upper 141.6 m of the ICDP Core 5017-1. The present study shows that aragonite and detritus laminae are thinner and occur at high frequency during MIS 3-2, while they are much thicker and less frequent during MIS 1. By analyzing multiple climate-connected factors, we propose that significant lake-level drops, enhanced dust input, and low vegetative cover in the drainage basin during the last deglaciation (22-11.6 ka) have considerably increased erodible materials in the Dead Sea watershed. We find a decoupling existed between the significant lake-level drop/lake size reduction and lamina thickness change during the last deglaciation. We argue that during the last glacial and the Holocene, the variation of lamina thickness at the multiple-millennium scale was not controlled directly by the lake-level/size change. We interpret this decoupling implying the transport capacity of flash-floods is low and might be saturated by the oversupply of erodible materials, and indicating a transport-limited regime during the time period. We suggest that the observed thickness and frequency distribution of aragonite-detritus laminae points to the high frequency of small-magnitude floods during the last glacial period, in contrast to low frequency, but large-magnitude floods during the Holocene.</p>

scholarly journals Climatic and in-cave influences on δ18O and δ13C in a stalagmite from northeastern India through the last deglaciation

2017 ◽  
Vol 88 (3) ◽  
pp. 458-471 ◽  
Author(s):  
Franziska A. Lechleitner ◽  
Sebastian F.M. Breitenbach ◽  
Hai Cheng ◽  
Birgit Plessen ◽  
Kira Rehfeld ◽  
...  
Keyword(s):  
Late Glacial ◽  
Masking Effect ◽  
Last Deglaciation ◽  
Local Conditions ◽  
The Holocene ◽  
Oxygen And Carbon Isotope ◽  
Ne India ◽  
Precipitation Seasonality ◽  
Stable Oxygen ◽  
The Last Deglaciation

AbstractNortheastern (NE) India experiences extraordinarily pronounced seasonal climate, governed by the Indian summer monsoon (ISM). The vulnerability of this region to floods and droughts calls for detailed and highly resolved paleoclimate reconstructions to assess the recurrence rate and driving factors of ISM changes. We use stable oxygen and carbon isotope ratios (δ18O and δ13C) from stalagmite MAW-6 from Mawmluh Cave to infer climate and environmental conditions in NE India over the last deglaciation (16–6ka). We interpret stalagmite δ18O as reflecting ISM strength, whereas δ13C appears to be driven by local hydroclimate conditions. Pronounced shifts in ISM strength over the deglaciation are apparent from the δ18O record, similarly to other records from monsoonal Asia. The ISM is weaker during the late glacial (LG) period and the Younger Dryas, and stronger during the Bølling-Allerød and Holocene. Local conditions inferred from the δ13C record appear to have changed less substantially over time, possibly related to the masking effect of changing precipitation seasonality. Time series analysis of the δ18O record reveals more chaotic conditions during the late glacial and higher predictability during the Holocene, likely related to the strengthening of the seasonal recurrence of the ISM with the onset of the Holocene.

scholarly journals Antarctic temperature and CO<sub>2</sub>: near-synchrony yet variable phasing during the last deglaciation

2018 ◽  
Author(s):  
Jai Chowdhry Beeman ◽  
Léa Gest ◽  
Frédéric Parrenin ◽  
Dominique Raynaud ◽  
Tyler J. Fudge ◽  
...  
Keyword(s):  
Phase Relationship ◽  
Ice Cores ◽  
Complex Nature ◽  
Temperature Phase ◽  
Last Deglaciation ◽  
The Holocene ◽  
Uncertainty Range ◽  
Major Transition ◽  
The Last Deglaciation ◽  
Temperature Proxy

Abstract. The last deglaciation, which occurred from 18,000 to 11,000 years ago, is the most recent large natural climatic variation of global extent. With accurately dated paleoclimate records, we can investigate the timings of related variables in the climate system during this major transition. Here, we use an accurate relative chronology to compare regional temperature proxy data and global atmospheric CO2 as recorded in Antarctic ice cores. We build a stack of temperature variations by averaging the records from five ice cores distributed across Antarctica, and develop a volcanic synchronization to compare it with the high-resolution, robustly dated WAIS Divide CO2 record. We assess the CO2/Antarctic temperature phase relationship using a stochastic method to accurately identify the probable timings of abrupt changes in their trends. During the large, millenial-scale changes at the onset of the last deglaciation at 18 ka and the onset of the Holocene at 11.5 ka, Antarctic temperature most likely led CO2 by several centuries. A marked event in both series around 16 ka began with a rapid rise in CO2, which stabilized synchronously with temperature. CO2 and Antarctic temperature peaked nearly synchronously at 14.4 ka, the onset of the Antarctic Cold Reversal (ACR) period. And CO2 likely led Antarctic temperature by around 250 years at the end of the ACR. The five major changes identified for both series are coherent, and synchrony is within the 2 σ uncertainty range for all of the changes except the Holocene onset. But the often-multimodal timings, centennial-scale substructures, and likely-variable phasings we identify testify to the complex nature of the two series, and of the mechanisms driving the carbon cycle and Antarctic temperature during the deglaciation.

The Impact on Europe of Large-Scale Climatic Changes: The Onset of Glaciation and the Last Deglaciation

1986 ◽  
pp. 28-44 ◽  
Author(s):  
J. C. Duplessy ◽  
L. Labeyrie ◽  
J. Moyes ◽  
J. L. Turon ◽  
J. Duprat ◽  
...  
Keyword(s):  
Large Scale ◽  
Climatic Changes ◽  
Last Deglaciation ◽  
The Last Deglaciation ◽  
The Impact

scholarly journals Seemingly divergent sea surface temperature proxy records in the central Mediterranean during the last deglaciation

2013 ◽  
Vol 9 (3) ◽  
pp. 1375-1383 ◽  
Author(s):  
M.-A. Sicre ◽  
G. Siani ◽  
D. Genty ◽  
N. Kallel ◽  
L. Essallami
Keyword(s):  
Adriatic Sea ◽  
Planktonic Foraminifera ◽  
Sea Surface ◽  
Last Deglaciation ◽  
Central Mediterranean ◽  
Proxy Record ◽  
Proxy Records ◽  
The Last Deglaciation ◽  
Temperature Proxy ◽  
Two Temperature

Abstract. Sea surface temperatures (SSTs) were reconstructed over the last 25 000 yr using alkenone paleothermometry and planktonic foraminifera assemblages from two cores of the central Mediterranean Sea: the MD04-2797 core (Siculo–Tunisian channel) and the MD90-917 core (South Adriatic Sea). Comparison of the centennial scale structure of the two temperature signals during the last deglaciation period reveals significant differences in timing and amplitude. We suggest that seasonal changes likely account for seemingly proxy record divergences during abrupt transitions from glacial to interglacial climates and for the apparent short duration of the Younger Dryas (YD) depicted by the alkenone time series, a feature that has already been stressed in earlier studies on the Mediterranean deglaciation.

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