The 4.2 ka event in the central Mediterranean: new data from a Corchia speleothem (Apuan Alps, central Italy)

Isola, Ilaria; Zanchetta, Giovanni; Drysdale, Russell N.; Regattieri, Eleonora; Bini, Mónica; Bajo, Petra; Hellström, John; Baneschi, Ilaria; Lionello, Piero; Woodhead, Jon; Greig, Alan

doi:10.5194/cp-15-135-2019

Cited by 35 publications

(35 citation statements)

References 95 publications

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“…Between 4.2 and 3.8 kyr cal BP, the anthropogenic indicator index of Lake Ledro, which is the closest anthropogenic record in the region, shows no human impact . The long-term increase of the SCTF at that period is, thus, supposed to be linked to a transition toward regionally wetter climate conditions (Isola et al, 2019). Here, the increase of the SCTF is synchronous with the increases that were observed on other Alpine Lakes flood chronicles (Fig.…”

Section: Accepted Manuscriptmentioning

confidence: 52%

Holocene-long record of flood frequency in the Southern Alps (Lake Iseo, Italy) under human and climate forcing

Rapuc

Sabatier

Arnaud

et al. 2019

Global and Planetary Change

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Develle, et al.. Holocene-long record of flood frequency in the Southern Alps (Lake Iseo, Italy) under human and climate forcing. Global and Planetary Change, Elsevier, 2019, pp.Abstract A high-resolution sedimentological and geochemical analysis of a 21 m sediment sequence of Lake Iseo (Southern Alps, Italy) allowed for the reconstruction of the long-term flood frequency by visual identification of the event layers over the last 12 kyr cal BP. In a previous study that was undertaken on another sediment core from Lake Iseo, these layers were attributed to extreme surface runoff events. However, in this former core, large mass-wasting deposits that induce significant hiatuses did not permit a continuous record of flood events to be established. Such disturbances were absent in the core studied in the present paper. This permitted to establish a high-resolution continuous Holocene record. Based on the flood chronicle and sedimentological and XRF geochemical analyses, ACCEPTED MANUSCRIPT A C C E P T E D M A N U S C R I P Twe found evidence of a major palaeohydrological transition at approximately 3.8 kyr cal BP, which was previously described as occurring in the western Mediterranean region. The oldest part of the record indeed presents a very low frequency of flood events (< 1 flood/century), while after 4 kyr cal BP, the flood frequency increased. This pattern appears to be in agreement with other Southern Alpine paleo flood records. The transition is interpreted as a nonlinear climate response to the orbital-driven gradual decrease in summer insolation at 60°N, which together with the influence of the Mediterranean mesoscale precipitation events, is typical for the Mediterranean climate. However, the comparison of the flood record with the archaeological and historical data from the watershed suggests that human activity during the Roman period in the vicinity of the main tributaries also influenced the flood frequency. Even in a large Alpine lake and more than 2000 years ago, extreme precipitation events that were recorded through the sedimentation process can hence be impacted by the anthropization of the catchment area pointing the requirement of deeper studies of Earth surface critical zone pluri-millennial dynamics.

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Section: Accepted Manuscriptmentioning

confidence: 52%

Holocene-long record of flood frequency in the Southern Alps (Lake Iseo, Italy) under human and climate forcing

Rapuc

Sabatier

Arnaud

et al. 2019

Global and Planetary Change

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“…At Lago Grande di Monticchio, a slight decrease in AP is recorded (−5 %) just before a gap in the pollen record from 4 to 3.5 ka (Allen et al, 2002) that may have contributed to masking the 4.2 ka event. At Lago Trifoglietti, the authors report an intense dry episode around 4.2 ka shown by the reconstructed annual precipitation record, which is not visible in the pollen record (Joannin et al, 2012). One possible explanation for this discrepancy is that in this mountain area a high mean annual precipitation (ca.…”

Section: Discussionmentioning

confidence: 90%

“…Lago Trifoglietti (1048 m a.s.l.) is part of a natural highaltitude lacustrine system located in the Calabria region (Joannin et al, 2012). The closest meteorological station indicates a mean annual precipitation of 1850 mm.…”

Section: Lago Grande DImentioning

confidence: 99%

The 4.2 ka event in the vegetation record of the central Mediterranean

Rita

Magri

2019

Clim. Past

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Abstract. In this paper, the variation in forest cover in the central Mediterranean region, reflected by percentage changes in the arboreal pollen record, has been examined in relation to the 4.2 ka event. A total of 36 well-dated and detailed pollen records from latitudes between 45 and 36∘ N were selected and their vegetation dynamics between 5 and 3 ka examined in relation to the physiographic and climatic features of the study area and to the influence of human activity on past vegetation, as suggested by anthropogenic pollen indicators. We have found that the sites located between 43 and 45∘ N do not show any significant vegetation change in correspondence with the 4.2 ka event. Several sites located on the Italian Peninsula between 39 and 43∘ N show a marked opening of the forest, suggesting a vegetation response to the climate instability of the 4.2 ka event. Between 36 and 39∘ N, a forest decline is always visible around 4.2 ka, and in some cases it is dramatic. This indicates that this region was severely affected by a climate change towards arid conditions that lasted a few hundred years and was followed by a recovery of forest vegetation in the Middle Bronze Age. Human activity, especially intense in southern Italy, may have been favored by this natural opening of vegetation. In Sardinia and Corsica, no clear change in vegetation is observed at the same time. We suggest that during the 4.2 ka event southern Italy and Tunisia were under the prevalent influence of a north African climate system characterized by a persistent high-pressure cell.

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“…However, this interpretation runs counter to the speleothem evidence from central Mediterranean indicating drier conditions (Renella, Corchia, and Mavri Trypa;Drysdale et al, 2006;Regattieri et al, 2014;Finné et al, 2017). This is further confirmed by new speleothem data (stable isotopes and trace elements) reported by Isola et al (2019), from Apuan Alps in central Italy. Figure 9 shows the NAO index inferred by Olsen et al (2011); during the 4.2 ka BP Event, the NAO is mostly positive, if not particularly prominent, suggesting that NAO configuration alone would not be particularly useful to interpret this period of time.…”

Section: Is a Synthesis Possible?mentioning

confidence: 80%

The 4.2 ka BP Event in the Mediterranean region: an overview

et al. 2019

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The Mediterranean region and the Levant have returned some of the clearest evidence of a climatically dry period occurring around 4200 years ago. However, some regional evidence is controversial and contradictory, and issues remain regarding timing, progression, and regional articulation of this event. In this paper, we review the evidence from selected proxies (sea-surface temperature, precipitation, and temperature reconstructed from pollen, δ 18 O on speleothems, and δ 18 O on lacustrine carbonate) over the Mediterranean Basin to infer possible regional climate patterns during the interval between 4.3 and 3.8 ka. The values and limitations of these proxies are discussed, and their potential for furnishing information on seasonality is also ex-plored. Despite the chronological uncertainties, which are the main limitations for disentangling details of the climatic conditions, the data suggest that winter over the Mediterranean involved drier conditions, in addition to already dry summers. However, some exceptions to this prevail -where wetter conditions seem to have persisted -suggesting regional heterogeneity in climate patterns. Temperature data, even if sparse, also suggest a cooling anomaly, even if this is not uniform. The most common paradigm to interpret the precipitation regime in the Mediterranean -a North Atlantic Oscillation-like pattern -is not completely satisfactory to interpret the selected data.

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The 4.2 ka event in the central Mediterranean: new data from a Corchia speleothem (Apuan Alps, central Italy)

Cited by 35 publications

References 95 publications

Holocene-long record of flood frequency in the Southern Alps (Lake Iseo, Italy) under human and climate forcing

Holocene-long record of flood frequency in the Southern Alps (Lake Iseo, Italy) under human and climate forcing

The 4.2 ka event in the vegetation record of the central Mediterranean

The 4.2 ka BP Event in the Mediterranean region: an overview

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