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A model for archaeologically relevant Holocene climate impacts in the Aegean-Levantine region (easternmost Mediterranean)

A model for archaeologically relevant Holocene climate impacts in the Aegean-Levantine region (easternmost Mediterranean)
A model for archaeologically relevant Holocene climate impacts in the Aegean-Levantine region (easternmost Mediterranean)
A repeating pattern of multi-centennial-scale Holocene climate events has been widely (globally) documented, and they were termed Rapid Climate Change (RCC) events. Non-seasalt potassium ion (K+) series in Greenland ice cores provide well-constrained timings for the events, and a direct timing relationship has been inferred between these events and the frequency of northerly cold polar/continental air outbreaks over the eastern Mediterranean Sea through gaps in the mountain ranges along the northern margin of the basin. There also appears to be a remarkable timing agreement with major archaeological turnover events in the Aegean/Levantine region. Yet no physically consistent assessment exists for understanding the regional climatic impacts of the events around this critical region. We present a simple 2-dimensional Lagrangian model, which yields a broad suite of physically coherent simulations of the impacts of frequency changes in winter-time northerly air outbreaks over the Aegean/Levantine region. We validate this with existing reconstructions from palaeoclimate proxy data, with emphasis on well-validated sea-surface temperature reconstructions and a highly resolved cave speleothem stable oxygen isotope record from Lebanon. Given that the RCCs were clearly marked by negative sea surface temperature anomalies in the region, we find that the predominant climatic impacts of this winter-time mechanism were “cold and wet,” in contrast with intercalated “warmer and more arid” conditions of non-RCC periods. More specifically, the RCCs are found to be periods of highly variable conditions, with an overall tendency toward cold and wet conditions with potential for flash flooding and for episodic snow-cover at low altitudes, at least in the lower-altitude (lower 1–1.5 km) regions of Crete and the Levant. The modelled winter-anomaly process cannot address underlying longer-term, astronomically forced trends, or the relatively warm and arid anomalies in between RCCs. The latter require further study, for example with respect to potential (summer-time?) extension of evaporative subtropical conditions over the region. Finally, our results imply that the “amount effect” observed in Levantine cave δ18O (and precipitation or drip-water δ18O) may not reflect the conventional concept related to temperature-dependent fractionation and Rayleigh distillation. Instead, it appears to arise from a complex and somewhat counter-intuitive mixing, in shifting proportionalities, between advected (external) and evaporated (Mediterranean) moisture.
0277-3791
38-53
Rohling, Eelco J.
a2a27ef2-fcce-4c71-907b-e692b5ecc685
Marino, Gianluca
40d6f3f2-0905-4c0f-8eb9-6d577b2833bb
Grant, Katharine M.
bc18079c-59af-45a0-9747-798c79a77c76
Mayewski, Paul A.
f54b7e29-788d-42b2-b286-2e78383e862f
Weninger, Bernhard
998a638b-3099-41b5-8b05-a03bb0c2e3a2
Rohling, Eelco J.
a2a27ef2-fcce-4c71-907b-e692b5ecc685
Marino, Gianluca
40d6f3f2-0905-4c0f-8eb9-6d577b2833bb
Grant, Katharine M.
bc18079c-59af-45a0-9747-798c79a77c76
Mayewski, Paul A.
f54b7e29-788d-42b2-b286-2e78383e862f
Weninger, Bernhard
998a638b-3099-41b5-8b05-a03bb0c2e3a2

Rohling, Eelco J., Marino, Gianluca, Grant, Katharine M., Mayewski, Paul A. and Weninger, Bernhard (2019) A model for archaeologically relevant Holocene climate impacts in the Aegean-Levantine region (easternmost Mediterranean). Quaternary Science Reviews, 208, 38-53. (doi:10.1016/j.quascirev.2019.02.009).

Record type: Article

Abstract

A repeating pattern of multi-centennial-scale Holocene climate events has been widely (globally) documented, and they were termed Rapid Climate Change (RCC) events. Non-seasalt potassium ion (K+) series in Greenland ice cores provide well-constrained timings for the events, and a direct timing relationship has been inferred between these events and the frequency of northerly cold polar/continental air outbreaks over the eastern Mediterranean Sea through gaps in the mountain ranges along the northern margin of the basin. There also appears to be a remarkable timing agreement with major archaeological turnover events in the Aegean/Levantine region. Yet no physically consistent assessment exists for understanding the regional climatic impacts of the events around this critical region. We present a simple 2-dimensional Lagrangian model, which yields a broad suite of physically coherent simulations of the impacts of frequency changes in winter-time northerly air outbreaks over the Aegean/Levantine region. We validate this with existing reconstructions from palaeoclimate proxy data, with emphasis on well-validated sea-surface temperature reconstructions and a highly resolved cave speleothem stable oxygen isotope record from Lebanon. Given that the RCCs were clearly marked by negative sea surface temperature anomalies in the region, we find that the predominant climatic impacts of this winter-time mechanism were “cold and wet,” in contrast with intercalated “warmer and more arid” conditions of non-RCC periods. More specifically, the RCCs are found to be periods of highly variable conditions, with an overall tendency toward cold and wet conditions with potential for flash flooding and for episodic snow-cover at low altitudes, at least in the lower-altitude (lower 1–1.5 km) regions of Crete and the Levant. The modelled winter-anomaly process cannot address underlying longer-term, astronomically forced trends, or the relatively warm and arid anomalies in between RCCs. The latter require further study, for example with respect to potential (summer-time?) extension of evaporative subtropical conditions over the region. Finally, our results imply that the “amount effect” observed in Levantine cave δ18O (and precipitation or drip-water δ18O) may not reflect the conventional concept related to temperature-dependent fractionation and Rayleigh distillation. Instead, it appears to arise from a complex and somewhat counter-intuitive mixing, in shifting proportionalities, between advected (external) and evaporated (Mediterranean) moisture.

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Rohling_et_al-2019_QSR - Accepted Manuscript
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Accepted/In Press date: 5 February 2019
e-pub ahead of print date: 14 February 2019
Published date: 1 March 2019

Identifiers

Local EPrints ID: 428486
URI: https://eprints.soton.ac.uk/id/eprint/428486
ISSN: 0277-3791
PURE UUID: 6bc8974b-50a2-4959-a8e8-93691e7c5d1e
ORCID for Eelco J. Rohling: ORCID iD orcid.org/0000-0001-5349-2158

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Date deposited: 28 Feb 2019 17:30
Last modified: 10 Dec 2019 01:55

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