Mediterranean Sea climatic indices: monitoring long term variability and climate changes

Abstract. We present a new product composed of a set of thermohaline climatic indices from 1950 to 2015 for the Mediterranean Sea such as decadal temperature and salinity anomalies, their mean values over selected depths, decadal ocean heat and salt content anomalies at selected depth layers as well as their long times series. It is produced from a new high-resolution climatology of temperature and salinity on a 1/8° regular grid based on historical high quality in situ observations. Ocean heat and salt content differences between 1980–2015 and 1950–1979 are compared for evaluation of the climate shift in the Mediterranean Sea. The spatial patterns of heat and salt content shifts demonstrate in greater detail than ever before that the climate changes differently in the several regions of the basin. Long time series of heat and salt content for the period 1950 to 2015 are also provided which indicate that in the Mediterranean Sea there is a net mean volume warming and salting since 1950 with acceleration during the last two decades. The time series also show that the ocean heat content seems to fluctuate on a cycle of about 40 years and seems to follow the Atlantic Multidecadal Oscillation climate cycle indicating that the natural large scale atmospheric variability could be superimposed on to the warming trend. This product is an observations-based estimation of the Mediterranean climatic indices. It relies solely on spatially interpolated data produced from in-situ observations averaged over decades in order to smooth the decadal variability and reveal the long term trends with more accuracy. It can provide a valuable contribution to the modellers' community, next to the satellite-based products and serve as a baseline for the evaluation of climate-change model simulations contributing thus to a better understanding of the complex response of the Mediterranean Sea to the ongoing global climate change. The product is available here: https://doi.org/10.5281/zenodo.1210100.

Download Full-text

Mediterranean Sea climatic indices: monitoring long-term variability and climate changes

Earth System Science Data ◽

10.5194/essd-10-1829-2018 ◽

2018 ◽

Vol 10 (4) ◽

pp. 1829-1842 ◽

Cited By ~ 7

Author(s):

Athanasia Iona ◽

Athanasios Theodorou ◽

Sarantis Sofianos ◽

Sylvain Watelet ◽

Charles Troupin ◽

...

Keyword(s):

Time Series ◽

Mediterranean Sea ◽

Climate Changes ◽

Salt Content ◽

Climatic Indices ◽

Long Time ◽

In Situ Observations ◽

The Mediterranean

Abstract. We present a new product composed of a set of thermohaline climatic indices from 1950 to 2015 for the Mediterranean Sea such as decadal temperature and salinity anomalies, their mean values over selected depths, decadal ocean heat and salt content anomalies at selected depth layers as well as their long time series. It is produced from a new high-resolution climatology of temperature and salinity on a 1∕8∘ regular grid based on historical high-quality in situ observations. Ocean heat and salt content differences between 1980–2015 and 1950–1979 are compared for evaluation of the climate shift in the Mediterranean Sea. The two successive periods are chosen according to the standard WMO climate normals. The spatial patterns of heat and salt content shifts demonstrate that the climate changes differently in the several regions of the basin. Long time series of heat and salt content for the period 1950 to 2015 are also provided which indicate that in the Mediterranean Sea there is a net mean volume warming and salinification since 1950 that has accelerated during the last two decades. The time series also show that the ocean heat content seems to fluctuate on a cycle of about 40 years and seems to follow the Atlantic Multidecadal Oscillation climate cycle, indicating that the natural large-scale atmospheric variability could be superimposed onto the warming trend. This product is an observation-based estimation of the Mediterranean climatic indices. It relies solely on spatially interpolated data produced from in situ observations averaged over decades in order to smooth the decadal variability and reveal the long-term trends. It can provide a valuable contribution to the modellers' community, next to the satellite-based products, and serve as a baseline for the evaluation of climate-change model simulations, thus contributing to a better understanding of the complex response of the Mediterranean Sea to the ongoing global climate change. The product is available in netCDF at the following sources: annual and seasonal T∕S anomalies (https://doi.org/10.5281/zenodo.1408832), annual and seasonal T∕S vertical averaged anomalies (https://doi.org/10.5281/zenodo.1408929), annual and seasonal areal density of OHC/OSC anomalies (https://doi.org/10.5281/zenodo.1408877), annual and seasonal linear trends of T∕S, OHC/OSC anomalies (https://doi.org/10.5281/zenodo.1408917), annual and seasonal time series of T∕S, OHC/OSC anomalies (https://doi.org/10.5281/zenodo.1411398), and differences of two 30-year averages of annual and seasonal T∕S, OHC/OSC anomalies (https://doi.org/10.5281/zenodo.1408903).

Download Full-text

Long-term monitoring programme of the hydrological variability in the Mediterranean Sea: a first overview of the HYDROCHANGES network

Ocean Science ◽

10.5194/os-9-301-2013 ◽

2013 ◽

Vol 9 (2) ◽

pp. 301-324 ◽

Cited By ~ 37

Author(s):

K. Schroeder ◽

C. Millot ◽

L. Bengara ◽

S. Ben Ismail ◽

M. Bensi ◽

...

Keyword(s):

Time Series ◽

Mediterranean Sea ◽

Sampling Interval ◽

Global Changes ◽

Hydrological Variability ◽

Long Term Monitoring ◽

The Mediterranean ◽

Set Up ◽

Term Monitoring

Abstract. The long-term monitoring of basic hydrological parameters (temperature and salinity), collected as time series with adequate temporal resolution (i.e. with a sampling interval allowing the resolution of all important timescales) in key places of the Mediterranean Sea (straits and channels, zones of dense water formation, deep parts of the basins), constitute a priority in the context of global changes. This led CIESM (The Mediterranean Science Commission) to support, since 2002, the HYDROCHANGES programme (http//www.ciesm.org/marine/programs/hydrochanges.htm), a network of autonomous conductivity, temperature, and depth (CTD) sensors, deployed on mainly short and easily manageable subsurface moorings, within the core of a certain water mass. The HYDROCHANGES strategy is twofold and develops on different scales. To get information about long-term changes of hydrological characteristics, long time series are needed. But before these series are long enough they allow the detection of links between them at shorter timescales that may provide extremely valuable information about the functioning of the Mediterranean Sea. The aim of this paper is to present the history of the programme and the current set-up of the network (monitored sites, involved groups) as well as to provide for the first time an overview of all the time series collected under the HYDROCHANGES umbrella, discussing the results obtained thanks to the programme.

Download Full-text

Mediterranean Tropical-Like Cyclones in Present and Future Climate

Journal of Climate ◽

10.1175/jcli-d-14-00339.1 ◽

2014 ◽

Vol 27 (19) ◽

pp. 7493-7501 ◽

Cited By ~ 40

Author(s):

Leone Cavicchia ◽

Hans von Storch ◽

Silvio Gualdi

Keyword(s):

Climate Change ◽

Mediterranean Sea ◽

Tropical Cyclones ◽

Dynamical Evolution ◽

Climate Change Scenarios ◽

Moderate Increase ◽

High Resolution Data ◽

The Mediterranean ◽

The One

Abstract The Mediterranean has been identified as one of the most responsive regions to climate change. It has been conjectured that one of the effects of a warmer climate could be to make the Mediterranean Sea prone to the formation of hurricanes. Already in the present climate regime, however, a few of the numerous low pressure systems that form in the area develop a dynamical evolution similar to the one of tropical cyclones. Even if their spatial extent is generally smaller and the life cycle shorter compared to tropical cyclones, such storms produce severe damage on the highly populated coastal areas surrounding the Mediterranean Sea. This study, based on the analysis of individual realistically simulated storms in homogeneous long-term and high-resolution data from multiple climate change scenarios, shows that the projected effect of climate change on Mediterranean tropical-like cyclones is decreased frequency and a tendency toward a moderate increase of intensity.

Download Full-text

Estimating Vertical Land Motion in Northern Adriatic Sea with Coastal Altimetry and In Situ Observations

10.5194/egusphere-egu2020-9754 ◽

2020 ◽

Author(s):

Francesco De Biasio ◽

Stefano Vignudelli ◽

Giorgio Baldin

Keyword(s):

Climate Change ◽

Sea Level Rise ◽

Mediterranean Sea ◽

Sea Level ◽

Coastal Zone ◽

Satellite Altimetry ◽

Data Sets ◽

Tide Gauges ◽

The Mediterranean

The European Space Agency, in the framework of the Sea Level Climate Change Initiative (SL_CCI), is developing consistent and long-term satellite-based data-sets to study climate-scale variations of sea level globally and in the coastal zone. Two altimetry data-sets were recently produced. The first product is generated over a grid of 0.25x0.25 degrees, merging and homogenizing the various satellite altimetry missions. The second product that is still experimental is along track over a grid of 0.35 km. An operational production of climate-oriented altimeter sea level products has just started in the framework of the European Copernicus Climate Change Service (C3S) and a daily-mean product is now available over a grid of 0.125x0.125 degrees covering the global ocean since 1993 to present.We made a comparison of the SL_CCI satellite altimetry dataset with sea level time series at selected tide gauges in the Mediterranean Sea, focusing on Venice and Trieste. There, the coast is densely covered by civil settlements and industrial areas with a strongly rooted seaside tourism, and tides and storm-related surges reach higher levels than in most of the Mediterranean Sea, causing damages and casualties as in the recent storm of November 12th, 2019: the second higher water registered in Venice since 1872. Moreover, in the Venice area the ground displacements exhibit clear negative trends which deepen the effects of the absolute sea level rise.Several authors have pointed out the synergy between satellite altimetry and tide gauges to corroborate evidences of ground displacements. Our contribution aims at understanding the role played by subsidence, estimated by the diffence between coastal altimetry and in situ measurements, on the local sea level rise. A partial validation of these estimates has been made against GPS-derived values, in order to distinguish the contributions of subsidence and eustatism. This work will contribute to identify problems and challenges to extend the sea level climate record to the coastal zone with quality comparable to the open ocean, and also to assess the suitability of altimeter-derived absolute sea levels as a tool to estimate subsidence from tide gauge measurement in places where permanent GPS receivers are not available.

Download Full-text

The Long-Term Wind and Wave Spectra of the Mediterranean Sea

24th International Conference on Offshore Mechanics and Arctic Engineering: Volume 2 ◽

10.1115/omae2005-67181 ◽

2005 ◽

Cited By ~ 1

Author(s):

Christos N. Stefanakos

Keyword(s):

Time Series ◽

Standard Deviation ◽

Stochastic Processes ◽

Mediterranean Sea ◽

Mean Value ◽

Residual Time ◽

Wave Data ◽

The Mediterranean ◽

Periodic Components

It is a well-known fact that long-term time series of wind and wave data are modelled as nonstationary stochastic processes with yearly periodic mean value and standard deviation (periodically correlated or cyclostationary stochastic processes). Using this model, the initial nonstationary series are decomposed to a seasonal (periodic) mean value m(t) and a residual time series W(t) multiplied by a seasonal (periodic) standard deviation s(t), of the form Y(t) = m(t) + s(t)W(t). The periodic components m(t) and s(t) are estimated using mean monthly values, and the residual time series W(t) is examined for stationarity. For this purpose, spectral densities of W(t) are obtained from different seasonal segments, calculated and compared with each other. It is shown that W(t) can indeed be considered stationary, and thus Y(t) can be considered periodically correlated. This analysis has been applied to model wind and wave data from several locations in the Mediterranean Sea. It turns out that the spectrum of W(t) is very weakly dependent on the site, a fact that might be useful for the geographic parameterization of wind and wave climate.

Download Full-text

Long term changes in the deep sea: examples from two Mediterranean Channels

10.5194/egusphere-egu2020-4499 ◽

2020 ◽

Author(s):

Katrin Schroeder ◽

Sana Ben Ismail ◽

Jacopo Chiggiato ◽

Mireno Borghini ◽

Stefania Sparnocchia

Keyword(s):

Climate Change ◽

Mediterranean Sea ◽

Deep Sea ◽

Deep Ocean ◽

Western Mediterranean ◽

Global Ocean ◽

Marginal Sea ◽

The Mediterranean

Climate change is one of the key topics of our century. The study of processes related to climate change in the atmosphere, the open ocean, the deep sea or even in shallow coastal waters require sustained long-term observations, often deploying sophisticated and expensive equipment. According to the Deep-Ocean Observing Strategy (DOOS, http://deepoceanobserving.org/), the deep ocean (below 200 m water depth) is the least observed, but largest habitat on our planet by volume and area. With more than 90% of anthropogenic heat imbalance absorbed by the oceans, monitoring long-term changes of its heat content, and over its full depth, is essential to quantify the planetary heat budget.The Mediterranean Sea is a mid-latitude marginal sea, particularly responsive to climate change as reported by recent studies. Straits and channels divide it into several sub-basins and the continuous monitoring of these choke points allows to intercept different water masses, and thus to document how they changed over time. This monitoring, in many cases, is done under the umbrella of the CIESM Hydrochanges program (http://www.ciesm.org/marine/programs/hydrochanges.htm). Here we report the long-term time series of physical data collected in two of these choke points: the Sardinia Channel (1900 m) and the Sicily Channel (400 m).The Sardinia Channel allows the Western Mediterranean Deep Water (WMDW) to enter the Tyrrhenian Sea (depths > 3000 m), connecting it with the Algerian Sea (depths > 2500 m). This water mass has experienced a significant increase of heat and salt content over the past decades, due both to a gradual process and to and abrupt event, called Western Mediterranean Transition (WMT). The monitoring at the sill (1900 m) of the Sardinia Channel since 2003 shows this very clearly, and the interannual trends are significantly stronger than the global average trends.The Sicily Channel (sill at 400 m) separates the Mediterranean in two main basins, the Eastern Mediterranean Sea and the Western Mediterranean Sea. Here the thermohaline properties of the Intermediate Water (IW) are monitored since 1993, showing increasing temperature and salinity trends at least one order of magnitude stronger than those observed at intermediate depths in the global ocean.We investigate the causes of the observed trends and in particular discuss the role of a changing climate over the Mediterranean, especially in the eastern basin, where the IW is formed. The long-term records in two Mediterranean channels reveal how fast the response to climate change can be in a marginal sea compared to the global ocean, and demonstrates the essential role of long time series in the ocean.

Download Full-text

Introduction: Process studies at the air–sea interface after atmospheric deposition in the Mediterranean Sea – objectives and strategy of the PEACETIME oceanographic campaign (May–June 2017)

Biogeosciences ◽

10.5194/bg-17-5563-2020 ◽

2020 ◽

Vol 17 (22) ◽

pp. 5563-5585

Author(s):

Cécile Guieu ◽

Fabrizio D'Ortenzio ◽

François Dulac ◽

Vincent Taillandier ◽

Andrea Doglioli ◽

...

Keyword(s):

Atmospheric Deposition ◽

Mediterranean Sea ◽

Anthropogenic Sources ◽

Dust Deposition ◽

Action Strategy ◽

Process Studies ◽

In Situ Observations ◽

The Mediterranean ◽

First Time

Abstract. In spring, the Mediterranean Sea, a well-stratified low-nutrient–low-chlorophyll region, receives atmospheric deposition by both desert dust from the Sahara and airborne particles from anthropogenic sources. Such deposition translates into a supply of new nutrients and trace metals for the surface waters that likely impact biogeochemical cycles. However, the relative impacts of the processes involved are still far from being assessed in situ. After summarizing the knowledge on dust deposition and its impact on the Mediterranean Sea biogeochemistry, we present in this context the objectives and strategy of the PEACETIME project and cruise. Atmospheric and marine in situ observations and process studies have been conducted in contrasted areas encountering different atmospheric deposition context, including a dust deposition event that our dedicated “fast-action” strategy allowed us to catch. Process studies also include artificial dust seeding experiments conducted on board in large tanks in three ecoregions of the open waters of the Mediterranean Sea for the first time. This paper summarizes the work performed at sea and the type of data acquired in the atmosphere, at the air–sea interface and in the water column. An overview of the results presented in papers of this special issue (and in some others published elsewhere) is presented.

Download Full-text

Analysis of a 44-year hindcast for the Mediterranean Sea: comparison with altimetry and in situ observations

Scientia Marina ◽

10.3989/scimar.2011.75n1071 ◽

2010 ◽

Vol 75 (1) ◽

pp. 71-86 ◽

Cited By ~ 16

Author(s):

Enrique Vidal-Vijande ◽

Ananda Pascual ◽

Bernard Barnier ◽

Jean-Marc Molines ◽

Joaquín Tintoré

Keyword(s):

Mediterranean Sea ◽

In Situ Observations ◽

The Mediterranean

Download Full-text

Process studies at the air-sea interface after atmospheric deposition in the Mediterranean Sea: objectives and strategy of the PEACETIME oceanographic campaign (May–June 2017)

10.5194/bg-2020-44 ◽

2020 ◽

Cited By ~ 3

Author(s):

Cécile Guieu ◽

Fabrizio D'Ortenzio ◽

François Dulac ◽

Vincent Taillandier ◽

Andrea Doglioli ◽

...

Keyword(s):

Atmospheric Deposition ◽

Mediterranean Sea ◽

Saharan Dust ◽

Anthropogenic Sources ◽

Dust Deposition ◽

Process Studies ◽

In Situ Observations ◽

The Mediterranean ◽

First Time

Abstract. In spring, the Mediterranean Sea, a well-stratified low nutrient low chlorophyll region, receives atmospheric deposition both desert dust from the Sahara and airborne particles from anthropogenic sources. Such deposition translates into a supply of new nutrients and trace metals for the surface waters that likely impact biogeochemical cycles. However, the quantification of the impacts and the processes involved are still far from being assessed in situ. In this paper, we provide a state of the art regarding dust deposition and its impact on the Mediterranean Sea biogeochemistry and we describe in this context the objectives and strategy of the PEACETIME project and cruise, entirely dedicated to filling this knowledge gap. Our strategy to go a step forward than in previous approaches in understanding these impacts by catching a real deposition event at sea is detailed. The PEACETIME oceanographic campaign took place in May–June 2017 and we describe how we were able to successfully adapt the planned transect in order to sample a Saharan dust deposition event, thanks to a dedicated strategy, so-called Fast Action. That was successful, providing, for the first time in our knowledge, a coupled atmospheric and oceanographic sampling before, during and after an atmospheric deposition event. Atmospheric and marine in situ observations and process studies have been conducted in contrasted area and we summarize the work performed at sea, the type of data acquired and their valorization in the papers published in the special issue.

Download Full-text