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

2018 ◽  
Vol 10 (4) ◽  
pp. 1829-1842 ◽  
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).

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

2018 ◽  
Author(s):  
Athanasia Iona ◽  
Athanasios Theodorou ◽  
Sarantis Sofianos ◽  
Sylvain Watelet ◽  
Charles Troupin ◽  
...  
Keyword(s):  
Climate Change ◽  
Time Series ◽  
Mediterranean Sea ◽  
Climate Changes ◽  
Salt Content ◽  
Climatic Indices ◽  
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 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.

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

Ocean Science ◽  
2013 ◽  
Vol 9 (2) ◽  
pp. 301-324 ◽  
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.

scholarly journals Aerosol decadal trends – Part 2: In-situ aerosol particle number concentrations at GAW and ACTRIS stations

2013 ◽  
Vol 13 (2) ◽  
pp. 895-916 ◽  
Author(s):  
A. Asmi ◽  
M. Collaud Coen ◽  
J. A. Ogren ◽  
E. Andrews ◽  
P. Sheridan ◽  
...  
Keyword(s):  
Time Series ◽  
Aerosol Particle ◽  
Particle Number ◽  
Cloud Condensation Nuclei ◽  
Temperature Changes ◽  
Long Time ◽  
Modelling Studies ◽  
Infrastructure Project

Abstract. We have analysed the trends of total aerosol particle number concentrations (N) measured at long-term measurement stations involved either in the Global Atmosphere Watch (GAW) and/or EU infrastructure project ACTRIS. The sites are located in Europe, North America, Antarctica, and on Pacific Ocean islands. The majority of the sites showed clear decreasing trends both in the full-length time series, and in the intra-site comparison period of 2001–2010, especially during the winter months. Several potential driving processes for the observed trends were studied, and even though there are some similarities between N trends and air temperature changes, the most likely cause of many northern hemisphere trends was found to be decreases in the anthropogenic emissions of primary particles, SO2 or some co-emitted species. We could not find a consistent agreement between the trends of N and particle optical properties in the few stations with long time series of all of these properties. The trends of N and the proxies for cloud condensation nuclei (CCN) were generally consistent in the few European stations where the measurements were available. This work provides a useful comparison analysis for modelling studies of trends in aerosol number concentrations.

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

2005 ◽  
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.

scholarly journals 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)

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.

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

2010 ◽  
Vol 75 (1) ◽  
pp. 71-86 ◽  
Author(s):  
Enrique Vidal-Vijande ◽  
Ananda Pascual ◽  
Bernard Barnier ◽  
Jean-Marc Molines ◽  
Joaquín Tintoré
Keyword(s):  
Mediterranean Sea ◽  
In Situ Observations ◽  
The Mediterranean

scholarly journals 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)

2020 ◽  
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.

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

2012 ◽  
Vol 9 (2) ◽  
pp. 1741-1812 ◽  
Author(s):  
K. Schroeder ◽  
C. Millot ◽  
L. Bengara ◽  
S. Ben Ismail ◽  
M. Bensi ◽  
...  
Keyword(s):  
Time Series ◽  
Mediterranean Sea ◽  
Time Scales ◽  
Sampling Interval ◽  
Global Changes ◽  
Hydrological Variability ◽  
Long Term Monitoring ◽  
The Mediterranean ◽  
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 time scales) 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-depth (CTD) sensors, deployed on mainly short and easily manageable sub-surface moorings. 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 detecting links between them at shorter time scales that may provide extremely valuable information about the functioning of the Mediterranean Sea. Here we present the history of the programme and the current setup of the network (monitored sites, involved groups) and provide an overview of all the available time series, discussing some of the results obtained thanks to the programme.

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