Papers by Giulia Margaritelli
Climatic variability over the last 3000 years in the central - western Mediterranean Sea (Menorca Basin) detected by planktonic foraminifera and stable isotope records
Planktonic foraminifera response to Sapropel S1 in the south Adriatic Sea, 2019
La ricostruzione della temperatura superficiale del mare (SST) degli ultimi millenni nell'area me... more La ricostruzione della temperatura superficiale del mare (SST) degli ultimi millenni nell'area mediterranea rappresenta un'importante sfida per documentare il possibile legame tra la variabilità del clima del passato e l'ascesa e la caduta delle antiche civiltà. Inoltre, nell'ultimo rapporto dell'IPCC (2018), è emersa l'esigenza di valutare i feedback climatici di episodi passati più caldi di quello attuale (1,5ºC-2°C). In questo contesto, presentiamo la ricostruzione dell'anomalia di SST degli ultimi cinque millenni basata sul rapporto Mg/Ca misurato su Globigerinoides ruber in un record proveniente dal settore occidentale del Canale di Sicilia (SW104-ND11, profondità: 475 m, Mediterraneo centrale). Questo nuovo record è stato confrontato con altri dati SST presenti in letteratura e provenienti da vari settori del Mediterraneo (Mare di Alboran, bacino di Minorca, Mar Egeo, emisfero settentrionale). Questo lavoro si pone l'obiettivo di gettare le basi per la discussione sull'impatto regionale del Periodo Romano e sul suo legame con lo sviluppo socio-economico dell'area Mediterranea. Secondo il record SST Mg/CaG.ruber, le temperature massime dell'Olocene superiore (22,7°C) sono state raggiunte a ca. 424 CE durante il Periodo Romano, dopo un trend generale di riscaldamento iniziato a ca. 3300 BCE interrotto da numerose oscillazioni a breve termine. Dopo il Periodo Romano, il record SST Mg / CaG.ruber presenta un trend di sostanziale raffreddamento che raggiunge i valori minimi di temperatura (18.2°C) a ca. 1673 CE, durante la Piccola Era Glaciale. Durante gli ultimi tre secoli, invece, il record SST Mg / CaG.ruber mostra un trend di riscaldamento fino ad arrivare ai giorni nostri (20.3 °C). Il confronto di questo record con altri dati SST ricostruiti sia su Mg/Ca che su Alkenoni e provenienti da diverse aree del Mediterraneo, supporta l'istaurarsi, in maniera omogenea, di condizioni calde a scala regionale tra il 100 BCE e il 500 CE, e documenta una chiara fase di riscaldamento di ca. 2 °C all'inizio del Periodo Romano, durante il cosiddetto "Roman Climatic Optimum". Questo periodo corrispose, storicamente, ad un importante incremento demografico durante l'Impero Romano. A ca. 600 CE viene, invece, viene registrata una fase di raffreddamento corrispondente all'evento della Late Antique Little Ice Age (LALIA); dopo questo evento, la ricostruzione SST Mg/CaG.ruber documenta la comparsa, a ca. 1180 CE, del famoso Periodo Caldo Medievale. Il raffreddamento associato alla Piccola Era Glaciale si è verificato tra il 1320 CE e ca. 1850 CE con un'anomalia negativa di ca. 2 °C. Il record studiato del Canale di Sicilia termina con un inversione, dal 1850 al 2014 CE, verso un riscaldamento di ca. 1°C probabilmente associato all'inizio del Periodo industriale / Periodo caldo moderno.
A B S T R A C T The climate evolution of the last 2700 years in the central-western Mediterranean... more A B S T R A C T The climate evolution of the last 2700 years in the central-western Mediterranean Sea has been reconstructed from marine sediment records by integrating planktonic foraminifera and geochemical signals. The results provide the characterization of six climatic phases: Balearic Bronze Age (BA), Roman Period (RP), Dark Age (DA), Medieval Climate Anomaly (MCA), Little Ice Age (LIA) and Industrial Period (IP). Paleoclimatic curve inferred from planktonic foraminifera associated with heavy values in δ 18 O Globigerinoides ruber during the BA document two cold intervals (spanning ca. 200 years) related to the Homeric and Greek solar minima. The dominance of Turborotalita quinqueloba –Globigerinita glutinata gr. and Globigerina bulloides during the RP suggest high fertility surface waters condition probably triggered by the increase in precipitation. During the DA, changes in the foraminiferal paleoclimate curve and oxygen isotope values display a cold –dry phase from 700 CE to the end of the DA (ca. 850 CE). This phase corresponds to the cold Roman IV solar minimum and marks the beginning of a long-term cooling interval that terminates during the LIA. The MCA is characterized by mild climatic conditions, interrupted at ca. 1050 CE by a cold-dry event. The gradually increase in abundance of G. ruber white characterize the IP warm period. The reconstructed climate evolution in the Balearic Basin results almost time-equivalent with the Mediterranean climate variability over the last 2700 years.
A new high-resolution pollen record, spanning the last five millennia, is presented from the Gulf... more A new high-resolution pollen record, spanning the last five millennia, is presented from the Gulf of Gaeta (Tyrrhenian Sea, central Italy), with the aim of verifying if any vegetation change occurred in the central Mediterranean region in relation to specific well-known global and/or regional climate events, including the 4.2 ka event, the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA), and to detect possible vegetation changes related to still under-investigated climate signals, for example the so-called " Bond 2 " cold event around 2.8 ka BP. The vegetation dynamics of the Gaeta record shows a recurrent pattern of forest increase and decline punctuating the mid-and late Holocene. When the timing of these patterns is compared with the climate proxy data available from the same core (planktonic foraminifera assemblages and oxygen stable isotope record) and with the NAO (North Atlantic Oscillation) index, it clearly appears that the main driver for the forest fluctuations is climate, which may even overshadow the effects of human activity. We have found a clear correspondence between phases with negative NAO index and forest declines. In particular, around 4200 cal BP, a drop in AP (Arboreal Pollen) confirms the clearance recorded in many sites in Italy south of 43 N. Around 2800 cal BP, a vegetation change towards open conditions is found at a time when the NAO index clearly shows negative values. Between 800 and 1000 AD, a remarkable forest decline, coeval with a decrease in the frequencies of both Castanea and Olea, matches a shift in the oxygen isotope record towards positive values, indicating cooler temperatures , and a negative NAO. Between 1400e1850 AD, in the time period chronologically corresponding to the LIA (Little Ice Age), the Gaeta record shows a clear decline of the forest cover, particularly evident after 1550 AD, once again in correspondence with negative NAO index.
It is well-known that the Holocene exhibits a millennial-scale climate variability. However, its ... more It is well-known that the Holocene exhibits a millennial-scale climate variability. However, its periodicity, spatio-temporal patterns and underlying processes are not fully deciphered yet. Here we focus on the central and western Mediterranean. We show that recurrent forest declines from the Gulf of Gaeta (central Tyrrhenian Sea) reveal a 1860-yr periodicity, consistent with a ca. 1800-yr climate fluctuation induced by large-scale changes in climate modes, linked to solar activity and/or AMOC intensity. We show that recurrent forest declines and dry events are also recorded in several pollen and palaeohydrological proxy-records in the south-central Mediterranean. We found coeval events also in several palaeohydrological records from the southwestern Mediterranean, which however show generally wet climate conditions, indicating a spatio-temporal hydrological pattern opposite to the south-central Mediterranean and suggesting that different expressions of climate modes occurred in the two regions at the same time. We propose that these opposite hydroclimate regimes point to a complex interplay of the prevailing or predominant phases of NAO-like circulation, East Atlantic pattern, and extension and location of the North African anticyclone. At a larger geographical scale, displacements of the ITCZ, modulated by solar activity and/or AMOC intensity, may have also indirectly influenced the observed pattern. Understanding the long-term trends and spatial patterns of climate variability in the current interglacial period, the Holocene, is crucial to assess the significance of ongoing climate change and future projections. Furthermore, taking into account the commonality of processes and mechanisms shared by climate models at all timescales, understanding the low frequency (millennial) component of past climate change is ultimately essential for improved predictions on all timescales. While it is well-known that the Holocene exhibits a millennial-scale climate variability, its periodicity, spatio-temporal patterns and underlying processes are not fully deciphered yet.
Global and Planetary Change, 2016
We present a high-resolution paleoclimatic and paleoenvironmental reconstruction of the last five... more We present a high-resolution paleoclimatic and paleoenvironmental reconstruction of the last five millennia from a shallow water marine sedimentary record from the central Tyrrhenian Sea (Gulf of Gaeta) using planktonic forami-nifera, pollen, oxygen stable isotope, tephrostratigrapy and magnetostratigrapy. This multiproxy approach allows to evidence and characterize nine time intervals associated with archaeological/cultural periods: Eneolithic (base of the core–ca. 2410 BCE), Early Bronze Age (ca. 2410 BCE–ca. 1900 BCE), Middle Bronze Age–Iron Age (ca. 1900 BCE–ca. 500 BCE), Roman Period (ca. 500 BCE–ca. 550 CE), Dark Age (ca. 550 CE–ca. 860 CE), Medieval Climate Anomaly (ca. 860 CE–ca. 1250 CE), Little Ice Age (ca. 1250 CE–ca. 1850 CE), Industrial Period (ca. 1850 CE–ca. 1950 CE), Modern Warm Period (ca. 1950 CE–present day). The reconstructed climatic evolution in the investigated sedimentary succession is coherent with the short-term climate variability documented at the Mediterranean scale. By integrating the planktonic foraminiferal turnover from carnivorous to herbivorous–opportunistic species, the oxygen isotope record and the pollen distribution, we document important modification from the onset of the Roman Period to the present-day. From ca. 500 CE upwards the documentation of the cooling trend punctuated by climate variability at secular scale evidenced by the short-term δ 18 O is very detailed. We hypothesise that the present day warm conditions started from the end of cold Maunder event. Additionally, we provide that the North Atlantic Oscillation (NAO) directly affected the central Mediterranean region during the investigated time interval.
We present a high-resolution paleoclimatic and paleoenvironmental reconstruction of the last five... more We present a high-resolution paleoclimatic and paleoenvironmental reconstruction of the last five millennia from a shallow water marine sedimentary record from the central Tyrrhenian Sea (Gulf of Gaeta) using planktonic forami-nifera, pollen, oxygen stable isotope, tephrostratigrapy and magnetostratigrapy. This multiproxy approach allows to evidence and characterize nine time intervals associated with archaeological/cultural periods: Eneolithic (base of the core–ca. 2410 BCE), Early Bronze Age (ca. 2410 BCE–ca. 1900 BCE), Middle Bronze Age–Iron Age (ca. 1900 BCE–ca. 500 BCE), Roman Period (ca. 500 BCE–ca. 550 CE), Dark Age (ca. 550 CE–ca. 860 CE), Medieval Climate Anomaly (ca. 860 CE–ca. 1250 CE), Little Ice Age (ca. 1250 CE–ca. 1850 CE), Industrial Period (ca. 1850 CE–ca. 1950 CE), Modern Warm Period (ca. 1950 CE–present day). The reconstructed climatic evolution in the investigated sedimentary succession is coherent with the short-term climate variability documented at the Mediterranean scale. By integrating the planktonic foraminiferal turnover from carnivorous to herbivorous–opportunistic species, the oxygen isotope record and the pollen distribution, we document important modification from the onset of the Roman Period to the present-day. From ca. 500 CE upwards the documentation of the cooling trend punctuated by climate variability at secular scale evidenced by the short-term δ 18 O is very detailed. We hypothesise that the present day warm conditions started from the end of cold Maunder event. Additionally, we provide that the North Atlantic Oscillation (NAO) directly affected the central Mediterranean region during the investigated time interval.
This study analyses the evolution of sea surface conditions during the last 2700 years in the cen... more This study analyses the evolution of sea surface conditions during the last 2700 years in the central-western Mediterranean Sea based on six records as measured on five short sediment cores from two sites north of Minorca (cores MINMC06 and HER-MC-MR3). Sea Surface Temperatures (SSTs) were obtained from alkenones and Globigerina bulloides-Mg/Ca ratios combined with δ18O measurements to reconstruct changes in the regional Evaporation–Precipitation (E–P) balance. We reviewed the G. bulloides Mg/Ca-SST calibration and re-adjusted it based on a set of core top measurements from the western Mediterranean Sea. According to the regional oceanographic data, the estimated Mg/Ca-SSTs are interpreted to reflect spring seasonal conditions mainly related to the April–May primary productivity bloom. In contrast, the Alkenone-SSTs signal likely integrates the averaged annual signal. A combination of chronological tools allowed synchronizing the records in a common age model. Subsequently a single anomaly stack record was constructed for each proxy, thus easing to identify the most significant and robust patterns. The warmest SSTs occurred during the Roman Period (RP), which was followed by a general cooling trend interrupted by several centennial-scale oscillations. This general cooling trend could be controlled by changes in the annual mean insolation. Whereas some particularly warm SST intervals took place during the Medieval Climate Anomaly (MCA) the Little Ice Age (LIA) was markedly unstable with some very cold SST events mostly during its second half. The records of the last centuries suggest that relatively low E–P ratios and cold SSTs dominated during negative North Atlantic Oscillation (NAO) phases, although SST records seem to present a close positive connection with the Atlantic Multidecadal Oscillation index (AMO).
Environmental Earth Sciences, 2016
Acta protozoologica
The benthic foraminiferal assemblages in Lake Varano (southern Italy) have been investigated in d... more The benthic foraminiferal assemblages in Lake Varano (southern Italy) have been investigated in detail. Statistical analyses en-able us to recognize two main biotopes and five sub-biotopes that reflect different ecological and environmental conditions. The assemblag-es mainly seem to be influenced by the hydrological (namely salinity) and sediment conditions in the lake. These biotopes are characterized by specific sub-assemblages and variations in relative species' abundances. The Outer Lake Biotope is affected by marine influence and is dominated by the foraminiferal species: Ammonia beccarii, Ammonia parkinsoniana and Aubignyna perlucida, which are more common in open water environments. In contrast, the Inner-Marginal Lake Biotope reflects more restricted conditions where low salinity values and sand are associated with high numbers of miliolids. These two main biotopes are thus subjected to different degrees of confinement and water residence times, both of which are relate...
Recent studies demonstrated that the Mediterranean continental shelf and, especially, the delta a... more Recent studies demonstrated that the Mediterranean continental shelf and, especially, the delta areas provide one of the most complete archive for monitoring the palaeoenvironmental and palaeoclimatic changes occurring in the last millennia. This work based on marine paleo proxies is aimed at documenting high-resolution time-series (decadal to century scale) for the Mediterranean Sea. It is included in the Italian Strategic Project NEXTDATA " A national system for recovery, storage, accessibility and dissemination of environmental and climatic data from mountain and marine areas " (http://www.nextdataproject.it). In this frame we studied several marine sites from central and south Tyrrhenian Sea, Sicily Channel, Taranto Gulf and Adriatic Sea considered key-areas for Mediterranean climatic reconstruction of the last two millennia. Here we focus on two continental shelf marine sites (Gulf of Gaeta and Gulf of Salerno) recovered at 93 and 103 meters water depth, respectively....
Proceedings of the Biological Society of Washington, 2014
In this study, the meiofaunal diversity in Lake Varano (southern Italy) is investigated in detail... more In this study, the meiofaunal diversity in Lake Varano (southern Italy) is investigated in detail. Using a statistical approach, these data were coupled with the physicochemical parameters of the bottom water and the sediment characteristics in order to understand the factors influencing meiofaunal biodiversity distribution. The lake is selectively influenced by different factors, namely: organic matter and grain-size, as well as water salinity. Although these assemblages appear to be poorly diversified, the diversity index values are similar to those generally reported in other transitional environments. Relatively higher values of both meiofaunal and benthic foraminiferal diversity were found in front of the Capoiale channel and in the inner part of the lake. The meiofaunal assemblages are mainly dominated by nematodes, copepods, and turbellarians. The benthic foraminiferal assemblages comprise 18 taxa and are mainly represented by calcareous forms, suggesting a relatively low degree of confinement and, consequently, moderately restricted conditions. These assemblages are comparable to the Ammonia assemblages with Haynesina germanica that are characteristic of lagoons along the Mediterranean coasts. On the basis of these findings, coupled with the biotic data, the lake can be regarded as an oligomesotrophic environment.
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Papers by Giulia Margaritelli