Rise Scenarios Research Articles

A high‐resolution study of tides in the Delaware Bay: Past conditions and future scenarios

Tides in the Delaware Bay (USA) have been modeled from 7000 years before present (7 ka) to the present day and for selected future sea‐level rise scenarios (100 years, 300 years). Historic bathymetries were constructed through use of glacial isostatic adjustment models and a very high spatial resolution (< 100 m) was used at the shoreline. Future bathymetries were obtained by extrapolating these glacial isostatic adjustment models and applying an additional eustatic sea‐level rise. It was found that tides in the lower bay have remained fairly constant through time but that tides in the upper bay have increased steadily from about 4 ka to the present day; a nearly 100% increase in total. The future runs demonstrated spatially complex behavior with tidal‐range changes of up to 10%.

Assessing risk associated with sea-level rise and storm surge—Redux

Scholarly, peer-reviewed analyses of reasonable sea-level rise and storm surge scenarios are essential to estimate risks to people and property and to identify sensible choices to reduce these risks. Herein we reply to Boretti and Parker, who suggest that sea levels are rising but not currently accelerating. In this respect, they take positions inconsistent with the majority of peer-reviewed semiempirical and model-based sea-level rise projections. Boretti’s comment largely focuses on an analysis of Australian tide gauges. The analysis, text and figures are basically a reproduction of a comment that he has provided previously to a completely different study from the Gold Coast of Australia (Cooper and Lemckert 2012); we are unclear on the relevance of this replicated Australian analysis to our study in the northeast United States. Both Boretti and Parker have drawn conclusions about sealevel rise trends in the United States through ‘visual scanning’ of graphs and by comparing relative sea-level rise trend estimates from years 1999 and 2006. Visual scanning is not a robust method, and it is highly unlikely that any conclusions based on analysis of such a short and particular period of time would pass peer review.

Need for adaptation strategy against global sea level rise: an example from Saudi coast of Arabian gulf

This paper reports sea level rise (SLR) scenarios causing land loss, environmental degradation and destruction of infrastructure in the Saudi coast of the Arabian Gulf. Human development structures such as, sea ports, desalination plants, industrial establishments, commercial buildings, fish farms etc. will be impacted, leading to great economic losses. A systematic analysis on the current environmental setting of east coast of Kingdom of Saudi Arabia (KSA) versus the existing infrastructure assets indicates that a 1 m sea level rise in Arabian Gulf affects approximately 650 km2 land area, along the Saudi coastline of ~1,800 km in 1:50,000 scale. Three simulation scenarios were created with respect to 1 m, 2 m and 3 m rises from the present mean sea level and its impacts were assessed. Maps depicting major infrastructure assets, ecologically sensitive elements, historical locations, anthropogenic zones, and Environmental Sensitivity Indices (ESI) were used for overlaying the sea level change map, in a Geographic Information System (GIS) platform. In general, the Jubail Marine Park area will have serious impact due to SLR. The inundation of low–lying lands will affect the mangroves species of Dawhat Ad Dafi, coral reefs, coastal salt marshes, groundwater aquifers, and fish stocks. The risk of inundation on the Abu Ali Island, given their status as marine sanctuary of international importance, is particularly high. As an adaptation strategy, it is proposed that the KSA should implement Integrated Coastal Zone Management Plan (ICZMP) for the Arabian Gulf coast without further delay for the protection of its vulnerable resources and for sustainable development.

Morphological evolution of the Guadiana estuary and intertidal zone in response to projected sea‐level rise and sediment supply scenarios

AbstractAnalysis of Holocene sediment accumulation in the Guadiana estuary (southern Portugal) during sea‐level rise since ca. 13 cal. ka BP was used to simulate the long‐term morphological evolution of the lower Guadiana estuary and the associated intertidal zone for 21st‐century predicted sea‐level rises. Three sea‐level rise scenarios given by the IPCC (2007) were used in the simulations of morphology using a large‐scale behaviour‐oriented modelling approach. Sedimentation rate scenarios were derived both from the Holocene evolution of the estuary and from a semi‐empirical estimation of present‐day sediment aggradation. Our results show that the net lateral expansion of the intertidal zone area would be about 3–5% of the present intertidal zone area for each 10 cm rise in sea level. Under constraints imposed by the lack of fluvial sediment supply, the lateral expansion of the landward boundary of the intertidal zone will occur mainly in the Portuguese margin of the Guadiana estuary, while submergence of the salt marshes will occur in the Spanish margin. Therefore the Spanish margin is highly vulnerable to both sea‐level rise and lack of sediment supply. Copyright © 2011 John Wiley & Sons, Ltd.

WATER TABLE FLUCTUATIONS IN A SLOPING AQUIFER: ANALYTICAL EXPRESSIONS FOR WATER EXCHANGE BETWEEN STREAM AND GROUND-WATER WITH SURFACE INFILTRATION

This paper presents an analytical solution of a linearized Boussinesq’s equation to obtain exact expressions for hydraulic head and flow rate in an unconfined downward sloping aquifer. The aquifer is in contact with a constant piezometric head at the left boundary and a stream at the right boundary whose water level is rising at a constant rate. The aquifer also receives a constant vertical recharge from the land surface due to rain infiltration. The governing equation is solved analytically using the Laplace transform to obtain the expressions for hydraulic head and flow rate. The proposed analytical solutions are verified with an earlier known solution for a horizontal aquifer with zero surface infiltration and found to be in complete agreement. The combined effect of slope and recharge on water table fluctuation and flow rate is studied by considering a numerical example. Model results establish the dependence of the water table fluctuations and flow rate on bed slope and surface recharge rate. The analytical expressions derived here can also represent an asymptotic scenario of either sudden rise or very slow rise in the stream water.

Sea‐level changes since the Last Glacial Maximum: an appraisal of the IPCC Fourth Assessment Report

AbstractThe IPCC Fourth Assessment Report (AR4) stated that global sea level rose by about 120 m between the Last Glacial Maximum (LGM) and 3–2 ka and did not rise again until the late 19th century. A review of relevant literature demonstrates that the rise may have been larger (by 10–15 m), that the timing of stabilisation is poorly constrained (within the last 7 ka BP), and that the onset of modern rates of sea‐level rise is not synchronous and uniform across the globe. The LGM lowstand as defined in the AR4 is based on the ‘classic’ Barbados sea‐level history, but the sea‐level curve from this island may not be an accurate ‘eustatic’ approximation if glacial isostatic adjustment (GIA) processes were significant, as suggested by various authors. The Barbados sea‐level curve revealed the existence of meltwater pulse (MWP) 1a at around 14 000 cal. a BP. Questions about the source and causal mechanism of MWP 1a are still being explored by field scientists and GIA modellers. These problems have direct relevance for contemporary measurements of ice mass changes, because space geodetic measurements rely on information provided by GIA models to separate land motion from ice mass changes. Global patterns of Holocene sea‐level change are controlled by regional sea‐level variability, not only through isostatic and tectonic processes, but also through steric effects, longer‐wavelength gravitational changes produced by changing ice–ocean mass flux and hemispheric‐scale perturbations in the Earth's rotation. ‘Eustasy’ is therefore merely a concept, not a measurable quantity. Constraining the late Holocene ice melt contribution to global sea‐level rise and determining regional sea‐level rise patterns in the 18th and 19th centuries are important future tasks for sea‐level scientists; these will establish the baseline contributions to 20th‐ and 21st‐century sea‐level rise and will help to determine the causes of modern rates of sea‐level rise. Constraining historical sea‐level accelerations and short‐term ice‐mass flux will aid models of ice‐sheet dynamics and help to reduce current uncertainties in future sea‐level predictions. The AR4 shows that regional sea‐level variability is clearly present in sea‐level change patterns for the past 50 a and an important challenge for the next IPCC assessment is to incorporate this variability into regional future sea‐level rise scenarios. Copyright © 2009 John Wiley & Sons, Ltd.

Antarctic ice‐sheet melting provides negative feedbacks on future climate warming

We show by using a three‐dimensional climate model, which includes a comprehensive representation of polar ice sheets, that on centennial to millennial time scales Antarctic Ice Sheet (AIS) can melt and moderate warming in the Southern Hemisphere, by up to 10°C regionally, in a 4 × CO2 scenario. This behaviour stems from the formation of a cold halocline in the Southern Ocean, which limits sea‐ice cover retreat under global warming and increases surface albedo, reducing local surface warming. Furthermore, we show that AIS melting, by decreasing Antarctic Bottom Water formation, restrains the weakening of the Atlantic meridional overturning circulation, which is a new illustration of the effect of the bi‐polar oceanic seesaw. Consequently, it appears that AIS melting strongly interacts with climate and ocean circulation globally. It is therefore necessary to account for this coupling in future climate and sea‐level rise scenarios.

Flood prediction and assessment of vulnerability risk in the southern coasts of the Caspian Sea

The southern part of the Caspian Sea shoreline in Iran with a length of 813 km has different topographic conditions. Owing to sea fluctuation, these zones have various dimensions in different times. During the last years, the Caspian Sea experienced enormous destructive rises. The historical information and tidal gauge measurements showed different ranges of sea rise from −30 m to −22 m from the mean sea level. On the other hand, the probable flooding zone is related to slope gradient of coasts. To help the determination of the probable flooding area owing to sea level rises, the coastal zones can be modelled using geographic information system (GIS) environment as vulnerability risk rates. These rates would be useful for making decisions in coastal management programs. This study examined different scenarios of sea rise to determine hazard-flooding rates in the coastal cities of the Mazandaran province and classified them based on vulnerability risk rates. The 1:2000 scale topographic maps of the coastal zones were prepared to extract topographic information and construct the coastal digital elevation model. With the presumption of half-metre sea rise scenarios, the digital elevation models classified eight scenarios from −26 to −22 m. The flooding areas in each scenario computed for 11 cities respectively. The vulnerability risk rate in each rise scenario was computed by dividing the flooded area of each scenario to city area. The results showed that in the first four scenarios, from −26 to −24 m, the Behshahr, Joibar, Neka and Babolsar cites would be more vulnerable than other cites. Moreover, for the second four scenarios from −24 to −22 m sea level rise scenario, only the coastal area of Chalous city would be vulnerable. It was also observed that the coastal region of Behshahr would be critical in total scenarios. Further studies would be necessary to complete this assessment by considering social-economic and land use information to estimate the exact hazardous and vulnerable zones.

Fluctuating deposition of ocean water drives plant function on coastal sand dunes

AbstractSea‐level rise will alter the hydrology of terrestrial coastal ecosystems. As such, it becomes increasingly important to decipher the present role of ocean water in coastal ecosystems in order to assess the coming effects of sea‐level rise scenarios. Sand dunes occur at the interface of land and sea. Traditionally, they are conceived as freshwater environments with rain and ground water as the only water sources available to vegetation. This study investigates the possibility of ocean water influx to dune soils and its effect on the physiology of sand dune vegetation. Stable isotopes are used to trace the path of ocean water from the soil to the vegetation. Soil salinity, water content and δ18O values are measured concurrently with stem water and leaf tissue of eight species during the wet and dry season and from areas proximal and distal to the ocean. Our results indicate the dune ecosystem is a mixed freshwater and marine water system characterized by oceanic influence on dune hydrology that is spatially heterogeneous and fluctuates temporally. Ocean water influx to soil occurs via salt spray in areas 5–12 m from the ocean during dry season. Accordingly, vegetation nearest to the sea demonstrate a plastic response to ocean water deposition including elevated integrated water use efficiency (δ13Cleaf) and uptake of ocean water that comprised up to 52% of xylem water. We suggest physiological plasticity in response to periodic ocean water influx may be a functional characteristic common to species on the leading edge of diverse coastal habitats and an important feature that should be included in modeling coastal ecosystems. Rising sea level would likely cause a repercussive landward shift of dune species in response to encroaching maritime influences. However, human development would restrict this process, potentially causing the demise of dune systems and the protection from land erosion they provide.

Prediction and prevention of the impacts of sea level rise on the Yangtze River Delta and its adjacent areas

The Yangtze River Delta region is characterized by high density of population and rapidly developing economy. There are low lying coastal plain and deltaic plain in this region. Thus, the study area could be highly vulnerable to accelerated sea level rise caused by global warming. This paper deals with the scenarios of the relative sea level rise in the early half period of the 21st century in the study area. The authors suggested that relative sea level would rise 25-50 cm by the year 2050 in the study area, of which the magnitude of relative sea level rise in the Yangtze River Delta would double the perspective worldwide average. The impacts of sea level rise include: (i) exacerbation of coastline recession in several sections and vertical erosion of tidal flat, and increase in length of eroding coastline; (ii) decrease in area of tidal flat and coastal wetland due to erosion and inundation; (iii) increase in frequency and intensity of storm surge, which would threaten the coastal protection works; (iv) reduction of drainage capacity due to backwater effect in the Lixiahe lowland and the eastern lowland of Taihu Lake region, and exacerbation of flood and waterlogging disasters; and (v) increase in salt water intrusion into the Yangtze Estuary. Comprehensive evaluation of sea level rise impacts shows that the Yangtze River Delta and eastern lowland of Taihu Lake region, especially Shanghai Municipality, belong in the district in the extreme risk category and the next is the northern bank of Hangzhou Bay, the third is the abandoned Yellow River delta, and the district at low risk includes the central part of north Jiangsu coastal plain and Lixiahe lowland.

Sensitivity of the stability of Scandinavian river flow regimes to a predicted temperature rise

A river flow regime, describing the average seasonal pattern of flow, reflects climatic and physiographic conditions in a basin. This average pattern can be stable, demonstrating the same seasonality in river flow from year to year, or unstable, when the flow regime alternates between a number of different seasonal patterns. Flow regime types have traditionally been used mainly for regionalization purposes. Being dependent on climate and physiography, seasonal flow regime patterns respond to changes in these two factors. In the context of a possible climate change, river flow regimes (both type and stability) can be used to test the sensitivity of this important river flow characteristic to a temperature rise. Such a sensitivity study is reported here on Norwegian runoff series modelled for three possible scenarios of a mean annual temperature rise in Scandinavia of +1°, +2° and +3°C and for different altitudes. The concept of entropy is applied to quantify the stability of the seasonal patterns. The study shows that the majority of seasonal flow regimes are very sensitive to the temperature rises studied. Regimes with a snowmelt source of flow formation become more unstable, while regime types with a rain source become more stable.