Projected sea level rise and changes in extreme storm surge and wave events during the 21st century in the region of Singapore

Singapore is an island state with considerable population, industries, commerce and transport located in coastal areas at elevations less than 2 m making it vulnerable to sea-level rise. Mitigation against future inundation events requires a quantitative assessment of risk. To address this need, regional projections of changes in (i) long-term mean sea level and (ii) the frequency of extreme storm surge and wave events have been combined to explore potential changes to coastal flood risk over the 21st century. Local changes in time mean sea level were evaluated using the process-based climate model data and methods presented in the IPCC AR5. Regional surge and wave solutions extending from 1980 to 2100 were generated using ~ 12 km resolution surge (Nucleus for European Modelling of the Ocean – NEMO) and wave (WaveWatchIII) models. Ocean simulations were forced by output from a selection of four downscaled (~ 12 km resolution) atmospheric models, forced at the lateral boundaries by global climate model simulations generated for the IPCC AR5. Long-term trends in skew surge and significant wave height were then assessed using a generalised extreme value model, fit to the largest modelled events each year. An additional atmospheric solution downscaled from the ERA-Interim global reanalysis was used to force historical ocean model simulations extending from 1980–2010, enabling a quantitative assessment of model skill. Simulated historical sea surface height and significant wave height time series were compared to tide gauge data and satellite altimetry data respectively. Central estimates of the long-term mean sea level rise at Singapore by 2100 were projected to be 0.52 m (0.74 m) under the RCP 4.5 (8.5) scenarios respectively. Trends in surge and significant wave height 2 year return levels were found to be statistically insignificant and/or physically very small under the more severe RCP8.5 scenario. We conclude that changes to long-term mean sea level constitute the dominant signal of change to the projected inundation risk for Singapore during the 21st century. We note that the largest recorded surge residual in the Singapore Strait of ~ 84 cm lies between the central and upper estimates of sea level rise by 2100, highlighting the vulnerability of the region

Potential impacts of climate change on the primary production of regional seas: A comparative analysis of five European seas

Regional seas are potentially highly vulnerable to climate change, yet are the most directly societally important regions of the marine environment. The combination of widely varying conditions of mixing, forcing, geography (coastline and bathymetry) and exposure to the open-ocean makes these seas subject to a wide range of physical processes that mediates how large scale climate change impacts on these seas’ ecosystems. In this paper we explore the response of five regional sea areas to potential future climate change, acting via atmospheric, oceanic and terrestrial vectors. These include the Barents Sea, Black Sea, Baltic Sea, North Sea, Celtic Seas, and are contrasted with a region of the Northeast Atlantic. Our aim is to elucidate the controlling dynamical processes and how these vary between and within these seas. We focus on primary production and consider the potential climatic impacts on: long term changes in elemental budgets, seasonal and mesoscale processes that control phytoplankton’s exposure to light and nutrients, and briefly direct temperature response. We draw examples from the MEECE FP7 project and five regional model systems each using a common global Earth System Model as forcing. We consider a common analysis approach, and additional sensitivity experiments. Comparing projections for the end of the 21st century with mean present day conditions, these simulations generally show an increase in seasonal and permanent stratification (where present). However, the first order (low- and mid-latitude) effect in the open ocean projections of increased permanent stratification leading to reduced nutrient levels, and so to reduced primary production, is largely absent, except in the NE Atlantic. Even in the two highly stratified, deep water seas we consider (Black and Baltic Seas) the increase in stratification is not seen as a first order control on primary production. Instead, results show a highly heterogeneous picture of positive and negative change arising from complex combinations of multiple physical drivers, including changes in mixing, circulation and temperature, which act both locally and non-locally through advection

Marine ecosystem response to the Atlantic Multidecadal Oscillation.

Against the backdrop of warming of the Northern Hemisphere it has recently been acknowledged that North Atlantic temperature changes undergo considerable variability over multidecadal periods. The leading component of natural low-frequency temperature variability has been termed the Atlantic Multidecadal Oscillation (AMO). Presently, correlative studies on the biological impact of the AMO on marine ecosystems over the duration of a whole AMO cycle (∼60 years) is largely unknown due to the rarity of continuously sustained biological observations at the same time period. To test whether there is multidecadal cyclic behaviour in biological time-series in the North Atlantic we used one of the world's longest continuously sustained marine biological time-series in oceanic waters, long-term fisheries data and historical records over the last century and beyond. Our findings suggest that the AMO is far from a trivial presence against the backdrop of continued temperature warming in the North Atlantic and accounts for the second most important macro-trend in North Atlantic plankton records; responsible for habitat switching (abrupt ecosystem/regime shifts) over multidecadal scales and influences the fortunes of various fisheries over many centuries

The influence of low-frequency variability and long-term trends in north atlantic sea surface temperature on irish waters

Sea surface temperature (SST) time-series collected in Irish waters between 1850 and 2007 exhibit a warming trend averaging 0.3 degrees C. The strongest warming has occurred since 1994, with the warmest years in the record being 2005, 2006, and 2007. The warming trend is superimposed on significant interannual to multidecadal-scale variability, linked to basin-scale oscillations of the ocean-atmosphere system. The dominant modes of low-frequency variability in North Atlantic SST records, investigated using an empirical orthogonal function (EOF) analysis, correspond to the Atlantic Multidecadal Oscillation (AMO), the East Atlantic Pattern (EAP), and the North Atlantic Oscillation (NAO) index, respectively, accounting for 23, 16, and 9% of the total variance in the dataset. Interannual variability in Irish SST records is dominated by the AMO, which, currently in its warm phase, explains approximately half of the current warm anomaly in the record. The EAP and the NAO influence variability in Irish SST time-series on a smaller scale, with the EAP also contributing to the current warm anomaly. After resolving the prevalent oscillatory modes of variability in the SST record, the underlying warming trend compares well with the global greenhouse effect warming trend. The anthropogenic contribution to the current warm anomaly in Irish SSTs was estimated at 0.41 degrees C for 2006, and this is predicted to increase annually

Interannual and regional variability of ecosystem dynamics in the BlackSea

A three-dimensional hydrodynamic ecosystem model developed for the Black Sea was used to investigate theinfluence of anthropogenic drivers on marine ecosystem functioning in the Black Sea with a special focus onregional differences. Data from the ECMWF 40 Year Re-analysis global atmospheric circulation model (ERA-40)were used to force a coupled hydrodynamic ecosystem model (BIMS) for a hindcast simulation from 1980-2000.Model skill was assessed by model comparisons with SeaWiFS surface chlorophyll distributions. We studythe regional differences the introduction of invasive comb jelly Mnemiopsis leidyi has on modeled ecosystemdynamics as well as the regional influence of changing river nutrient loads on ecosystem dynamics.We can demonstrate clearly that the appearance of M. Leidyi changes ecosystem functioning through exertinggrazing pressure on zooplankton and thereby changing the seasonal cycle of phytoplankton and zooplanktonspecies significantly. On the north-western shelf this effect is less pronounced than in the southeast Black Sea,where zooplankton is grazed down more heavily, allowing for higher phytoplankton biomass. In addition, theBlack Sea ecosystem shows strong regional nitrate limitation, and high sensitivity to increased eutrophication:A 50% increase in nutrient loading causes a 48% increase in primary production in the eastern regions of theBlack Sea, while the north-western shelf reacts more moderately. Despite an increase in primary production,chlorophyll-a concentrations typically respond weakly to changes in nitrate availability. This indicates thatincreased grazing closely mirrors an increase in productivity. This is confirmed by an increase in zooplanktonbiomass. It is important to note that for this reason simulated chlorophyll concentration is not a good indicator ofeutrophication in the Black Sea. The reduction in the productivity of the entire Black Sea system associated with areduction in riverine nutrient loadings is much greater than the increase in productivity associated with an increasein nutrient loadings. Hence the model simulations represent a Black Sea ecosystem, which is highly sensitive toa reduction in nutrient loadings, suggesting management of river water quality is vital for the improvement of theecosystem state of the Black Sea

Physical processes mediating climate change impacts on regional sea ecosystems

International audienceRegional seas are exceptionally vulnerable to climate change, yet are the most directly societally important regions of the marine environment. The combination of widely varying conditions of mixing, forcing, geography (coastline and bathymetry) and exposure to the open-ocean makes these seas subject to a wide range of physical processes that mediates how large scale climate change impacts on these seas' ecosystems. In this paper we explore these physical processes and their biophysical interactions, and the effects of atmospheric, oceanic and terrestrial change on them. Our aim is to elucidate the controlling dynamical processes and how these vary between and within regional seas. We focus on primary production and consider the potential climatic impacts: on long term changes in elemental budgets, on seasonal and mesoscale processes that control phytoplankton's exposure to light and nutrients, and briefly on direct temperature response. We draw examples from the MEECE FP7 project and five regional models systems using ECOSMO, POLCOMS-ERSEM and BIMS_ECO. These cover the Barents Sea, Black Sea, Baltic Sea, North Sea, Celtic Seas, and a region of the Northeast Atlantic, using a common global ocean-atmosphere model as forcing. We consider a common analysis approach, and a more detailed analysis of the POLCOMS-ERSEM model. Comparing projections for the end of the 21st century with mean present day conditions, these simulations generally show an increase in seasonal and permanent stratification (where present). However, the first order (low- and mid-latitude) effect in the open ocean projections of increased permanent stratification leading to reduced nutrient levels, and so to reduced primary production, is largely absent, except in the NE Atlantic. Instead, results show a highly heterogeneous picture of positive and negative change arising from the varying mixing and circulation conditions. Even in the two highly stratified, deep water seas (Black and Baltic Seas) the increase in stratification is not seen as a first order control on primary production. The approaches to downscaled experiment design and lessons learned from the MEECE project are also discussed

Physical processes mediating climate change impacts on regional sea ecosystems

Regional seas are exceptionally vulnerable to climate change, yet are the most directly societally important regions of the marine environment. The combination of widely varying conditions of mixing, forcing, geography (coastline and bathymetry) and exposure to the open-ocean makes these seas subject to a wide range of physical processes that mediates how large scale climate change impacts on these seas' ecosystems. In this paper we explore these physical processes and their biophysical interactions, and the effects of atmospheric, oceanic and terrestrial change on them. Our aim is to elucidate the controlling dynamical processes and how these vary between and within regional seas. We focus on primary production and consider the potential climatic impacts: on long term changes in elemental budgets, on seasonal and mesoscale processes that control phytoplankton's exposure to light and nutrients, and briefly on direct temperature response. We draw examples from the MEECE FP7 project and five regional models systems using ECOSMO, POLCOMS-ERSEM and BIMS_ECO. These cover the Barents Sea, Black Sea, Baltic Sea, North Sea, Celtic Seas, and a region of the Northeast Atlantic, using a common global ocean-atmosphere model as forcing. We consider a common analysis approach, and a more detailed analysis of the POLCOMS-ERSEM model