Periodic Reporting for period 1 - WATERISKULT (Climate change risk to underwater cultural heritage in stone)
Periodo di rendicontazione: 2022-09-01 al 2024-08-31
Anthropogenic climate change has multiple and diverse effects on seas and oceans. Besides the environmental, economic, social, and health implications, it has a dramatic impact also on underwater cultural heritage, which involves millions of submerged ruins, settlements, wrecks, and artifacts worldwide. The risk posed to their preservation, historical legacy, and component materials represents a global-scale issue. WATERISKULT provides the first quantitative assessment of the climate change risk to underwater cultural heritage, considering the impact of ocean acidification and extreme weather events on stone materials, which are among the most important natural resources exploited all through human history and prehistory. Adopting an interdisciplinary approach based on mixed field and laboratory experimentation, including laboratory simulations, field exposure tests, sampling, analysis, and monitoring, WATERISKULT explores the observed and predicted decay trends in underwater archaeological sites, controlled by the diverse characteristics of the stone materials and submarine environments. The results delivered address the deterioration amount, rate, forms, and dynamics, and the relevant driving forces and constraints. The findings allow comprehending the vulnerability of submarine archaeological sites and landscapes under the environmental stresses brought about by climate change.
The effects of ocean acidification on stone deterioration were investigated both in the natural environment and in controlled laboratory conditions. Carbonate rocks selected as representative among the historical materials most frequently used in cultural heritage were characterized for their petrographic, chemical, and technical properties and then monitored for one year immersed in seawater. The field experimentation was performed along the coasts of Ischia in southern Italy, where seawater pH is locally affected by submarine CO2 seeps. The laboratory experimentation was conducted setting seawater pH, temperature, and pressure in a custom-made Microenvironment Simulator. A range of pH values encompassing pre-industrial, current, and projected future levels was considered for all investigations, supported by chemical analyses of seawater. The time evolution of the stone surfaces was monitored by measuring material loss from erosion due to mineral dissolution and textural changes, quantified on 3D models acquired at regular steps; additional investigations involved mass losses, calcite saturation indexes computed by geochemical modeling, and biofouling. By this approach, a correlation was established among stone properties, decay, and seawater chemistry.
On the other hand, the effects of extreme weather events were examined by simulations of storm-driven sea currents in a laboratory flume, monitoring the decay of the same rock types exposed to high-intensity water flows with suspended sediment. The multi-hour experiments were run with a combination of different flow velocities and sediment concentration and grain size. Material loss from erosion and surface textural changes were again quantified by 3D modeling, aided by microscopic observations, establishing a correlation among stone properties, erosion and characteristics of flow and seabed sediments.
Underwater stone deterioration was also investigated by observing its patterns in archaeological sites of the Mediterranean Sea (Anse des Laurons in France, Baia in Italy, and Amathus in Cyprus). A range of microscopic and morphometric techniques were applied for achieving a comprehensive petrographic, microchemical, topographic, and biological characterization of samples from an array of archaeological stone surfaces. This provided a perspective on the different marine environments, stone substrates and their mineralogical and textural properties, and how these influence the decay. An overview of the main chemical changes, the distribution and frequency of occurrence of the organisms involved in stone biofouling, and the morphological changes they cause was obtained.
These results were disseminated in international and national conferences (seven, to date) and on the official project website, and are being summarized in three full peer-reviewed articles. They are open to a series of possible exploitations: in academia, from a conservation and archaeometric approach or even addressing the ecological and geomorphological implications for the submarine environment; by heritage stakeholders, for fine tuning long-term strategies and policies for underwater site protection; in science communication, for further raising public awareness about the diverse impacts of climate change.
On the other hand, the effects of extreme weather events were examined by simulations of storm-driven sea currents in a laboratory flume, monitoring the decay of the same rock types exposed to high-intensity water flows with suspended sediment. The multi-hour experiments were run with a combination of different flow velocities and sediment concentration and grain size. Material loss from erosion and surface textural changes were again quantified by 3D modeling, aided by microscopic observations, establishing a correlation among stone properties, erosion and characteristics of flow and seabed sediments.
Underwater stone deterioration was also investigated by observing its patterns in archaeological sites of the Mediterranean Sea (Anse des Laurons in France, Baia in Italy, and Amathus in Cyprus). A range of microscopic and morphometric techniques were applied for achieving a comprehensive petrographic, microchemical, topographic, and biological characterization of samples from an array of archaeological stone surfaces. This provided a perspective on the different marine environments, stone substrates and their mineralogical and textural properties, and how these influence the decay. An overview of the main chemical changes, the distribution and frequency of occurrence of the organisms involved in stone biofouling, and the morphological changes they cause was obtained.
These results were disseminated in international and national conferences (seven, to date) and on the official project website, and are being summarized in three full peer-reviewed articles. They are open to a series of possible exploitations: in academia, from a conservation and archaeometric approach or even addressing the ecological and geomorphological implications for the submarine environment; by heritage stakeholders, for fine tuning long-term strategies and policies for underwater site protection; in science communication, for further raising public awareness about the diverse impacts of climate change.
WATERISKULT highlights how ocean acidification may accelerate the deterioration of carbonate rocks in archaeological sites, leading to a surface recession in the order of hundreds of micrometers per year in extreme scenarios, much enhanced if compared to pre-industrial and present conditions. Erosion amount and rate is constrained, other than by seawater pH, by the specific stone texture (e.g. grain size) and technical properties (e.g. porosity and strength). Ocean acidification may also cause changes in the biofouling of archaeological surfaces, especially by calcifying organisms, implying a diminished extension and biodiversity. High risk to stone conservation is also predicted for the impact of high-intensity sea and ocean currents generated during extreme weather events, whose intensity and tracks are expected to change in the future. The most violent storms may erode up to tens of micrometers per hour from the stone surfaces, and completely change their morphological features. Stone decay is enhanced by faster water flows and coarser suspended sediments, other than being controlled by the material properties. These findings are completed by the overview of the causes and effects of the main decay processes currently observable and quantifiable in underwater archaeological sites, especially the biodeterioration and its surface and stratigraphic patterns; each of the epilithic and endolithic organisms involved (mainly algae, tubeworms, sponges, barnacles, and bryozoans) is characterized by a peculiar textural modification of the stone substrate where they grow, often irreversible.
The most significant progress beyond the state of the art lies in the first quantitative assessment of the underwater effects of ocean acidification and extreme weather events, which represents a theme underestimated in the scientific and public debate about cultural heritage. This novel information is crucial for understanding how heritage vulnerability will increase as the conditions of seas and oceans vary because of climate change and depending on different future scenarios of greenhouse gas emissions. In fact, WATERISKULT has both a political and scientific hoped impact: on one side, on intergovernmental, non-governmental, or governmental organizations involved in the management and protection of underwater sites and, in general, cultural heritage and the marine environment; on the other, on the activities of the IPCC as well as of heritage scientists, archaeologists, and other researchers interested in climate change and cultural heritage.
The most significant progress beyond the state of the art lies in the first quantitative assessment of the underwater effects of ocean acidification and extreme weather events, which represents a theme underestimated in the scientific and public debate about cultural heritage. This novel information is crucial for understanding how heritage vulnerability will increase as the conditions of seas and oceans vary because of climate change and depending on different future scenarios of greenhouse gas emissions. In fact, WATERISKULT has both a political and scientific hoped impact: on one side, on intergovernmental, non-governmental, or governmental organizations involved in the management and protection of underwater sites and, in general, cultural heritage and the marine environment; on the other, on the activities of the IPCC as well as of heritage scientists, archaeologists, and other researchers interested in climate change and cultural heritage.