Solar pacing of storm surges, coastal flooding and agricultural losses in the Central Mediterranean

Natural and Cultural Lost Landscape during the Holocene along the Central Tyrrhenian Coast (Italy)

Landscape evolution over the last 8000 years in three areas located along Tuscany, Latium, and Campania coasts (central Tyrrhenian) has been deduced through a morphological, stratigraphical, and historical approach considering the physical evolution and human activity. Between 8000 and 6000 yr BP, the Sea Level Rise (SLR) dominated and, near the river mouths, inlets occurred. In the Tuscany area, Mt. Argentario was an island and to SE of the Ansedonia promontory a lagoon occurred. The areas were covered by a dense forest and the human influence was negligible. Between 6000 and 4000 yr BP, humans organized settlements and activities, and a general coastline progradation occurred. A tombolo linked Mt. Argentario to the mainland. In the Tiber and Campania areas, coastal lakes and a strand plain developed. Between 4000 and 3000 yr BP, near Mt. Argentario, two tombolos enclosed a wide lagoon. At the SE of the Ansedonia promontory, the lagoon split into smaller water bodies. In the Tiber and Campania areas, delta cusps developed. The anthropogenic presence was widespread and forests decreased. During the last 3000 years, anthropic forcing increased when the Etruscans and Romans changed the territory through towns, salt pans, and ports. After the Roman period, natural forcing returned to dominate until the birth of the Italian State and technological evolution.

A Holocene Sedimentary Record and the Impact of Sea-Level Rise in the Karst Lake Velo Blato and the Wetlands on Pag Island (Croatia)

Lakes in coastal lowland areas represent a critically vulnerable environment as a transitional space between freshwater and seawater environments. The paleoenvironmental reconstruction and anthropogenic impact are assessed through the lake sediment cores from Velo, Malo, and Kolanjsko Blato using multi-proxy analyses (sedimentological, mineralogical, geochemical, 137Cs and ostracod analyses, and AMS 14C radiocarbon dating). The freshwater lake Velo Blato was formed at 8100 cal yr BP due to rising groundwater levels as a consequence of sea-level rise. The brackish conditions in Lake Velo Blato started at 7100 cal yr BP, giving the index point for the sea-level curve of 7-m lower than present. Lead concentrations showed slightly increased values in the last 1800 cal yr BP, while the spike in Malo Blato lake sediments probably derived from bird hunting with lead bullets. Kolanjsko Blato sediment core archives the sediment record of the last 2050 years, which represents a shallow brackish coastal wetland under marine influence. Enrichment factors showed the accumulation of Cu, Hg, P, Pb, S, and Zn in the sediments from Kolanjsko Blato in the last 650 cal yr BP, which coincides with the high organic carbon content, and in sediments from Malo Blato after the lake’s formation (from the depth of 20 cm upwards). Anthropogenic Cu introduced into the Kolanjsko Blato sediments is the highest in the surface sample. Surficial sediments from Velo Blato are characterized by the high organic carbon, S, P, and N content, indicating high productivity and eutrophication which led to occasional anoxic conditions on the lake bottom in the last 200 years.

Climate pacing of millennial sea-level change variability in the central and western Mediterranean

Future warming in the Mediterranean is expected to significantly exceed global values with unpredictable implications on the sea-level rise rates in the coming decades. Here, we apply an empirical-Bayesian spatio-temporal statistical model to a dataset of 401 sea-level index points from the central and western Mediterranean and reconstruct rates of sea-level change for the past 10,000 years. We demonstrate that the mean rates of Mediterranean industrial-era sea-level rise have been significantly faster than any other period since ~4000 years ago. We further highlight a previously unrecognized variability in Mediterranean sea-level change rates. In the Common Era, this variability correlates with the occurrence of major regional-scale cooling/warming episodes. Our data show a sea-level stabilization during the Late Antique Little Ice Age cold event, which interrupted a general rising trend of ~0.45 mm a⁻¹ that characterized the warming episodes of the Common Era. By contrast, the Little Ice Age cold event had only minor regional effects on Mediterranean sea-level change rates.

How sea-level in the western Mediterranean reacts to climate changes is not well known. Here, the authors present a regional reconstruction and show that temperatures influenced sea-level change rates during the Holocene, while recent sea-level rise is happening faster than during any other period of the last 4000 years.

Sustainability of Coastal Agriculture under Climate Change

Climatic and non-climatic stressors, such as temperature increases, rainfall fluctuations, population growth and migration, pollution, land-use changes and inadequate gender-specific strategies, are major challenges to coastal agricultural sustainability. In this paper, we discuss all pertinent issues related to the sustainability of coastal agriculture under climate change. It is evident that some climate-change-related impacts (e.g., temperature and rainfall) on agriculture are similarly applicable to both coastal and non-coastal settings, but there are other factors (e.g., inundation, seawater intrusion, soil salinity and tropical cyclones) that particularly impact coastal agricultural sustainability. Coastal agriculture is characterised by low-lying and saline-prone soils where spatial competition with urban growth is an ever-increasing problem. We highlight how coastal agricultural viability could be sustained through blending farmer perceptions, adaptation options, gender-specific participation and integrated coastal resource management into policy ratification. This paper provides important aspects of the coastal agricultural sustainability, and it can be an inspiration for further research and coastal agrarian planning.

A millennium-long reconstruction of damaging hydrological events across Italy

Damaging hydrological events are extreme phenomena with potentially severe impacts on human societies. Here, we present the hitherto longest reconstruction of damaging hydrological events for Italy, and for the whole Mediterranean region, revealing 674 such events over the period 800–2017. For any given year, we established a severity index based on information in historical documentary records, facilitating the transformation of the data into a continuous time-series. Episodes of hydrological extremes disrupted ecosystems during the more severe events by changing landforms. The frequency and severity of damaging hydrological events across Italy were likely influenced by the mode of the Atlantic Multidecadal Variability (AMV), with relatively few events during the warm Medieval Climate Anomaly dominated by a positive phase of the AMV. More frequent and heavier storms prevailed during the cold Little Ice Age, dominated by a more negative phase of the AMV. Since the mid-19^th century, a decreasing occurrence of exceptional hydrological events is evident, especially during the most recent decades, but this decrease is not yet unprecedented in the context of the past twelve centuries.

Holocene forest dynamics in central and western Mediterranean: periodicity, spatio-temporal patterns and climate influence

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 south-western 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.

Tsunamis in the geological record: Making waves with a cautionary tale from the Mediterranean

From 2000 to 2015, tsunamis and storms killed more than 430,000 people worldwide and affected a further >530 million, with total damages exceeding US$970 billion. These alarming trends, underscored by the tragic events of the 2004 Indian Ocean catastrophe, have fueled increased worldwide demands for assessments of past, present, and future coastal risks. Nonetheless, despite its importance for hazard mitigation, discriminating between storm and tsunami deposits in the geological record is one of the most challenging and hotly contended topics in coastal geoscience. To probe this knowledge gap, we present a 4500-year reconstruction of "tsunami" variability from the Mediterranean based on stratigraphic but not historical archives and assess it in relation to climate records and reconstructions of storminess. We elucidate evidence for previously unrecognized "tsunami megacycles" with three peaks centered on the Little Ice Age, 1600, and 3100 cal. yr B.P. (calibrated years before present). These ~1500-year cycles, strongly correlated with climate deterioration in the Mediterranean/North Atlantic, challenge up to 90% of the original tsunami attributions and suggest, by contrast, that most events are better ascribed to periods of heightened storminess. This timely and provocative finding is crucial in providing appropriately tailored assessments of coastal hazard risk in the Mediterranean and beyond.