Nikolaos Skliris
University of Southampton
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Publication
Featured researches published by Nikolaos Skliris.
Bulletin of the American Meteorological Society | 2015
Gabriele C. Hegerl; Emily Black; Richard P. Allan; William Ingram; Debbie Polson; Kevin E. Trenberth; Robin Chadwick; Phillip A. Arkin; Beena Balan Sarojini; Andreas Becker; Aiguo Dai; Paul J. Durack; David R. Easterling; Hayley J. Fowler; Elizabeth J. Kendon; George J. Huffman; Chunlei Liu; Robert Marsh; Mark New; Timothy J. Osborn; Nikolaos Skliris; Peter A. Stott; Pier Luigi Vidale; Susan Wijffels; Laura Wilcox; Kate M. Willett; Xuebin Zhang
AbstractUnderstanding observed changes to the global water cycle is key to predicting future climate changes and their impacts. While many datasets document crucial variables such as precipitation, ocean salinity, runoff, and humidity, most are uncertain for determining long-term changes. In situ networks provide long time series over land, but are sparse in many regions, particularly the tropics. Satellite and reanalysis datasets provide global coverage, but their long-term stability is lacking. However, comparisons of changes among related variables can give insights into the robustness of observed changes. For example, ocean salinity, interpreted with an understanding of ocean processes, can help cross-validate precipitation. Observational evidence for human influences on the water cycle is emerging, but uncertainties resulting from internal variability and observational errors are too large to determine whether the observed and simulated changes are consistent. Improvements to the in situ and satellit...
Ecological Modelling | 2003
Khalid Elkalay; Constantin Frangoulis; Nikolaos Skliris; Anne Goffart; Sylvie Gobert; Gilles Lepoint; Jean-Henri Hecq
Modelling of seagrasses can be an effective tool to assess factors regulating their growth. Growth and production model of Posidonia oceanica, the dominant submerged aquatic macrophyte occurring in the Bay of Calvi (Corsica, Ligurian Sea, Northwestern (NW) Mediterranean) was developed. The state variables are the above- and below-ground biomass of P. oceanica, the epiphyte biomass, and the internal nitrogen concentration of the whole plant. Light intensity and water temperature are the forcing variables. The model reproduces successfully seasonal growth and production for each variable at various depths (10, 20 and 30 m). The model can simulate also a number of consecutive years. Sensitivity analysis of model’s parameters showed that the maximum nitrogen quota nmax rate is the most sensitive parameter in this model. The results simulations imply that light intensity is one of the most important abiotic factors, the diminution of which can cause an important reduction in seagrass density.
Journal of Marine Systems | 2002
Nikolaos Skliris; Jean-Henri Hecq
A 3-D, unsteady, nonlinear, high-resolution model is used to estimate shelf/slope exchanges through Calvi Canyon (NW Corsica, Mediterranean Sea) in various regimes of stratification and wind patterns. To evaluate the alongshore and cross-shore fluxes within the canyon area as well as the water exchanges between the canyon and Calvi Bay, volume transports are computed at the sides of two closed, interconnected boxes encompassing the canyon on the shelf and slope domains. Model results show that water transports between Calvi Bay and the open sea are determined by flow modifications in the canyon area. The mean horizontal flow deviates southwestward upstream of the canyon, generating an onshore transport in the western part of Calvi Bay. Within the canyon, the circulation is cyclonic and is responsible for an offshore transport downstream of the canyon and in the eastern part of the bay. The effect of stratification is shown to limit the vertical extent of the influence of canyon topography so that the alongshore flow above the canyon is quasi-undisturbed in strong stratified conditions, resulting in weak cross-shore exchange. Wind events are shown to be responsible for a strong increase of cross-shore transports between the bay and the canyon area.
Scientific Reports | 2016
Nikolaos Skliris; Jan D. Zika; George Nurser; Simon A. Josey; Robert Marsh
A change in the cycle of water from dry to wet regions of the globe would have far reaching impact on humanity. As air warms, its capacity to hold water increases at the Clausius-Clapeyron rate (CC, approximately 7% °C−1). Surface ocean salinity observations have suggested the water cycle has amplified at close to CC following recent global warming, a result that was found to be at odds with state-of the art climate models. Here we employ a method based on water mass transformation theory for inferring changes in the water cycle from changes in three-dimensional salinity. Using full depth salinity observations we infer a water cycle amplification of 3.0 ± 1.6% °C−1 over 1950–2010. Climate models agree with observations in terms of a water cycle amplification (4.3 ± 2.0% °C−1) substantially less than CC adding confidence to projections of total water cycle change under greenhouse gas emission scenarios.
Journal of Climate | 2015
Jan D. Zika; Nikolaos Skliris; A. J. George Nurser; Simon A. Josey; Lawrence Mudryk; Frédéric Laliberté; Robert Marsh
The global water cycle leaves an imprint on ocean salinity through evaporation and precipitation. It has been proposed that observed changes in salinity can be used to infer changes in the water cycle. Here salinity is characterized by the distribution of water masses in salinity coordinates. Only mixing and sources and sinks of freshwater and salt can modify this distribution. Mixing acts to collapse the distribution, making saline waters fresher and fresh waters more saline. Hence, in steady state, there must be net precipitation over fresh waters and net evaporation over saline waters. A simple model is developed to describe the relationship between the breadth of the distribution, the water cycle, and mixing—the latter being characterized by an e-folding time scale. In both observations and a state-of-the-art ocean model, the water cycle maintains a salinity distribution in steady state with a mixing time scale of the order of 50 yr. The same simple model predicts the response of the salinity distribution to a change in the water cycle. This study suggests that observations of changes in ocean salinity could be used to infer changes in the hydrological cycle.
Archive | 2014
Nikolaos Skliris
The aim of this section is to provide a comprehensive overview of the research findings concerning the thermohaline circulation of the Mediterranean Sea. The decadal/inter-decadal variability and long-term evolution of the thermohaline properties of the Mediterranean Basin are extensively discussed. We focus on the major climate transient thermohaline events and their links to atmospheric variability and anthropogenic/environmental changes that dramatically changed the deep hydrology and strongly affected the marine ecosystems of the Mediterranean basin during the last 20 years. This section also includes a synthesis of the results of future projections of the thermohaline circulation derived by climate model simulations of the Mediterranean region covering the twenty-first century. The expected effects of the projected thermohaline circulation changes on the marine ecology are also discussed.
Geophysical Research Letters | 2016
Florian Sévellec; Bablu Sinha; Nikolaos Skliris
The nature of rogue events is their unlikelihood and the recent unpredicted decade-long slowdown in surface warming, the so-called hiatus, may be such an event. However, given decadal variability in climate, global surface temperatures were never expected to increase monotonically with increasing radiative forcing. Here surface air temperature from 20 climate models is analyzed to estimate the historical and future likelihood of hiatuses and “surges” (faster than expected warming), showing that the global hiatus of the early 21st century was extremely unlikely. A novel analysis of future climate scenarios suggests that hiatuses will almost vanish and surges will strongly intensify by 2100 under a “business as usual” scenario. For “CO2 stabilisation” scenarios, hiatus, and surge characteristics revert to typical 1940s values. These results suggest to study the hiatus of the early 21st century and future reoccurrences as rogue events, at the limit of the variability of current climate modelling capability.
Climate Dynamics | 2018
Nikolaos Skliris; Jan D. Zika; Leo Alexander Herold; Simon A. Josey; Robert Marsh
Changes in the Mediterranean water cycle since 1950 are investigated using salinity and reanalysis based air–sea freshwater flux datasets. Salinity observations indicate a strong basin-scale multi-decadal salinification, particularly in the intermediate and deep layers. Evaporation, precipitation and river runoff variations are all shown to contribute to a very strong increase in net evaporation of order 20–30%. While large temporal uncertainties and discrepancies are found between E–P multi-decadal trend patterns in the reanalysis datasets, a more robust and spatially coherent structure of multi-decadal change is obtained for the salinity field. Salinity change implies an increase in net evaporation of ~ 8 to 12% over 1950–2010, which is considerably lower than that suggested by air–sea freshwater flux products, but still largely exceeding estimates of global water cycle amplification. A new method based on water mass transformation theory is used to link changes in net evaporation over the Mediterranean Sea with changes in the volumetric distribution of salinity. The water mass transformation distribution in salinity coordinates suggests that the Mediterranean basin salinification is driven by changes in the regional water cycle rather than changes in salt transports at the straits.
Journal of Geophysical Research | 2016
Jeremy P. Grist; Simon A. Josey; Jan D. Zika; Dafydd Gwyn Evans; Nikolaos Skliris
A novel assessment of recent changes in air-sea freshwater fluxes has been conducted using a surface temperature-salinity framework applied to four atmospheric reanalyses. Viewed in the T-S space of the ocean surface, the complex pattern of the longitude-latitude space mean global Precipitation minus Evaporation (PME) reduces to three distinct regions. The analysis is conducted for the period 1979-2007 for which there is most evidence for a broadening of the (atmospheric) tropical belt. All four of the reanalyses display an increase in strength of the water cycle. The range of increase is between 2%-30% over the period analysed, with an average of 14%. Considering the average across the reanalyses, the water cycle changes are dominated by changes in tropical as opposed to mid-high latitude precipitation. The increases in the water cycle strength, are consistent in sign, but larger than in a 1% greenhouse gas run of the HadGEM3 climate model. In the model a shift of the precipitation/evaporation cells to higher temperatures is more evident, due to the much stronger global warming signal. The observed changes in freshwater fluxes appear to be reflected in changes in the T-S distribution of the Global Ocean. Specifically, across the diverse range of atmospheric reanalyses considered here, there was an acceleration of the hydrological cycle during 1979-2007 which led to a broadening of the oceans salinity distribution. Finally, although the reanalyses indicate that the warm temperature tropical precipitation dominated water cycle change, ocean observations suggest that ocean processes redistributed the freshening to lower ocean temperatures.
Archive | 2013
S. Sofianos; V. Vervatis; Nikolaos Skliris; Samuel Somot; A. Lascaratos; A. Mantziafou
Recent changes of the thermohaline circulation in the Eastern Mediterranean (i.e. the Eastern Mediterranean Transient) and older observations of the thermohaline structure of the Aegean-Levantine region (with events of dramatic changes of deep water characteristics) reveal the very sensitive character of the regional thermohaline circulation pattern. This and the long term variability of seawater characteristics in various Mediterranean basins show that the deep water mass formation processes in the region can be greatly affected by climate variability and the characteristics of the extreme atmospheric forcing events. Theoretical work and modeling experiments point out the effectiveness of extreme events and periods of abnormal atmospheric conditions to produce deep waters of different characteristics and different equilibrium depth. Studying the mechanisms involved in the air-sea interaction under extreme event conditions, with available observations and modeling techniques, and monitoring important sites of water mass formation becomes very important for understanding the regional dynamics of the water cycle and their effect on the climate of the whole Mediterranean Sea region.