Response of waves and coastline evolution to climate variability off the Niger Delta coast during the past 110 years

NASA Astrophysics Data System (ADS)

Dada, Olusegun A.; Li, Guangxue; Qiao, Lulu; Ma, Yanyan; Ding, Dong; Xu, Jishang; Li, Pin; Yang, Jichao

2016-08-01

River deltas, low-lying landforms that host critical economic infrastructures and diverse ecosystems as well as high concentrations of human population, are highly vulnerable to the effects of global climate change. In order to understand the wave climate, their potential changes and implication on coastline evolution for environment monitoring and sustainable management of the Niger Delta in the Gulf of Guinea, an investigation was carried out based on offshore wave statistics of an 110-year time series (1900-2010) dataset obtained from the ECMWF ERA-20C atmospheric reanalysis. Results of multivariate regression analyses indicate that interannual mean values of Hs and Tm trends tended to increase over time, especially in the western part of the delta coast, so that they are presently (1980 and 2010) up to 264 mm (300%) and 0.32 s (22%), respectively, higher than 80 years (1900-1930) ago. The maximum directions of the wave have become more westerly (southward) than southerly (westward) by up to 2° (33%) and the mean longshore sediment transport rate has increased by more than 8% over the last 80 years. The linear regression analysis for shoreline changes from 1987 to 2013 shows an erosional trend at the western part of the delta and accretional trends towards eastern part. The relationship between wave climate of the study area and atmospheric circulation using Pearson's correlation shows that the Atlantic Multidecadal Oscillation (AMO), North Atlantic Oscillation (NAO), East Atlantic pattern (EA) and El-Nino/Southern Oscillation (ENSO) Index explain significant proportion of the seasonal and annual wave variabilities compared to other indices. But it is most likely that the combination of these climatic indices acting together or separately constitutes a powerful and effective mechanism responsible for much of the variability of the offshore Niger Delta wave climate. The study concludes that changing wave climate off the Niger Delta has strong implications on the delta coastline changes. However, other processes (such as fluvial discharge variability due climatic variability and anthropogenic effect) may be acting concomitantly with changes in wave regime and associated littoral transport to influence shoreline evolution along the Niger Delta coast.

The response of the southwest Western Australian wave climate to Indian Ocean climate variability

NASA Astrophysics Data System (ADS)

Wandres, Moritz; Pattiaratchi, Charitha; Hetzel, Yasha; Wijeratne, E. M. S.

2018-03-01

Knowledge of regional wave climates is critical for coastal planning, management, and protection. In order to develop a regional wave climate, it is important to understand the atmospheric systems responsible for wave generation. This study examines the variability of the southwest Western Australian (SWWA) shelf and nearshore wind wave climate and its relationship to southern hemisphere climate variability represented by various atmospheric indices: the southern oscillation index (SOI), the Southern Annular Mode (SAM), the Indian Ocean Dipole Mode Index (DMI), the Indian Ocean Subtropical Dipole (IOSD), the latitudinal position of the subtropical high-pressure ridge (STRP), and the corresponding intensity of the subtropical ridge (STRI). A 21-year wave hindcast (1994-2014) of the SWWA continental shelf was created using the third generation wave model Simulating WAves Nearshore (SWAN), to analyse the seasonal and inter-annual wave climate variability and its relationship to the atmospheric regime. Strong relationships between wave heights and the STRP and the STRI, a moderate correlation between the wave climate and the SAM, and no significant correlation between SOI, DMI, and IOSD and the wave climate were found. Strong spatial, seasonal, and inter-annual variability, as well as seasonal longer-term trends in the mean wave climate were studied and linked to the latitudinal changes in the subtropical high-pressure ridge and the Southern Ocean storm belt. As the Southern Ocean storm belt and the subtropical high-pressure ridge shifted southward (northward) wave heights on the SWWA shelf region decreased (increased). The wave height anomalies appear to be driven by the same atmospheric conditions that influence rainfall variability in SWWA.

A new climate index controlling winter wave activity along the Atlantic coast of Europe: The West Europe Pressure Anomaly

NASA Astrophysics Data System (ADS)

Castelle, Bruno; Dodet, Guillaume; Masselink, Gerd; Scott, Tim

2017-02-01

A pioneering and replicable method based on a 66-year numerical weather and wave hindcast is developed to optimize a climate index based on the sea level pressure (SLP) that best explains winter wave height variability along the coast of western Europe, from Portugal to UK (36-52°N). The resulting so-called Western Europe Pressure Anomaly (WEPA) is based on the sea level pressure gradient between the stations Valentia (Ireland) and Santa Cruz de Tenerife (Canary Islands). The WEPA positive phase reflects an intensified and southward shifted SLP difference between the Icelandic low and the Azores high, driving severe storms that funnel high-energy waves toward western Europe southward of 52°N. WEPA outscores by 25-150% the other leading atmospheric modes in explaining winter-averaged significant wave height, and even by a largest amount the winter-averaged extreme wave heights. WEPA is also the only index capturing the 2013/2014 extreme winter that caused widespread coastal erosion and flooding in western Europe.

Resiliency of the Nation's Power Grid: Assessing Risks of Premature Failure of Large Power Transformers Under Climate Warming and Increased Heat Waves

NASA Astrophysics Data System (ADS)

Schlosser, C. A.; Gao, X.; Morgan, E.

2017-12-01

The aging pieces of our nation's power grid - the largest machine ever built - are at a critical time. Key assets in the transmission system, including large power transformers (LPTs), are approaching their originally designed lifetimes. Moreover, extreme weather and climate events upon which these design lifetimes are partially based are expected to change. In particular, more frequent and intense heat waves can accelerate the degradation of LPTs' insulation/cooling system. Thus, there are likely thousands of LPTs across the United States under increasing risk of premature failure - yet this risk has not been assessed. In this study, we investigate the impact of climate warming and corresponding shifts in heat waves for critical LPTs located in the Northeast corridor of the United States to assess: To what extent do changes in heat waves/events present a rising threat to the transformer network over the Northeast U.S. and to what extent can climate mitigation reduce this risk? This study focuses on a collection of LPTs with a high degree of "betweenness" - while recognizing other factors such as: connectivity, voltage rating, MVA rating, approximate price, weight, location/proximity to major transportation routes, and age. To assess the risk of future change in heat wave occurrence we use an analogue method, which detects the occurrence of heat waves based on associated large-scale atmospheric conditions. This method is compared to the more conventional approach that uses model-simulated daily maximum temperature. Under future climate warming scenarios, multi-model medians of both methods indicate strong increases in heat wave frequency during the latter half of this century. Under weak climate mitigation - the risks imposed from heat wave occurrence could quadruple, but a modest mitigation scenario cuts the increasing threat in half. As important, the analogue method substantially improves the model consensus through reduction of the interquartile range by a factor of three. The improved inter-model consensus is viewed as a promising step toward providing more actionable climate information. Ultimately - this technique could be applied to the entirety of the U.S. power grid as well as other weather extrema (e.g. precipitation, ice, and wind) as well as assess current and future topologies of any electricity system.

Ocean waves from tropical cyclones in the Gulf of Mexico and the effect of climate change

NASA Astrophysics Data System (ADS)

Appendini, C. M.; Pedrozo-Acuña, A.; Meza-Padilla, R.; Torres-Freyermuth, A.; Cerezo-Mota, R.; López-González, J.

2016-12-01

To generate projections of wave climate associated to tropical cyclones is a challenge due to their short historical record of events, their low occurrence, and the poor wind field resolution in General Circulation Models. Synthetic tropical cyclones provide an alternative to overcome such limitations, improving robust statistics under present and future climates. We use synthetic events to characterize present and future wave climate associated with tropical cyclones in the Gulf of Mexico. The NCEP/NCAR atmospheric reanalysis and the Coupled Model Intercomparison Project Phase 5 models NOAA/GFDL CM3 and UK Met Office HADGEM2-ES, were used to derive present and future wave climate under RCPs 4.5 and 8.5. The results suggest an increase in wave activity for the future climate, particularly for the GFDL model that shows less bias in the present climate, although some areas are expected to decrease the wave energy. The practical implications of determining the future wave climate is exemplified by means of the 100-year design wave, where the use of the present climate may result in under/over design of structures, since the lifespan of a structure includes the future wave climate period.

Extreme waves from tropical cyclones and climate change in the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Appendini, Christian M.; Pedrozo-Acuña, Adrian; Meza-Padilla, Rafael; Torres-Freyermuth, Alec; Cerezo-Mota, Ruth; López-González, José

2017-04-01

Tropical cyclones generate extreme waves that represent a risk to infrastructure and maritime activities. The projection of the tropical cyclones derived wave climate are challenged by the short historical record of tropical cyclones, their low occurrence, and the poor wind field resolution in General Circulation Models. In this study we use synthetic tropical cyclones to overcome such limitations and be able to characterize present and future wave climate associated with tropical cyclones in the Gulf of Mexico. Synthetic events derived from the NCEP/NCAR atmospheric reanalysis and the Coupled Model Intercomparison Project Phase 5 models NOAA/GFDL CM3 and UK Met Office HADGEM2-ES, were used to force a third generation wave model to characterize the present and future wave climate under RCP 4.5 and 8.5 escenarios. An increase in wave activity is projected for the future climate, particularly for the GFDL model that shows less bias in the present climate, although some areas are expected to decrease the wave energy. The practical implications of determining the future wave climate is exemplified by means of the 100-year design wave, where the use of the present climate may result in under/over design of structures, since the lifespan of a structure includes the future wave climate period.

A wall-free climate unit for acoustic levitators.

PubMed

Schlegel, M C; Wenzel, K-J; Sarfraz, A; Panne, U; Emmerling, F

2012-05-01

Acoustic levitation represents the physical background of trapping a sample in a standing acoustic wave with no contact to the wave generating device. For the last three decades, sample holders based on this effect have been commonly used for contact free handling of samples coupled with a number of analytical techniques. In this study, a wall-free climate unit is presented, which allows the control of the environmental conditions of suspended samples. The insulation is based on a continuous cold/hot gas flow around the sample and thus does not require any additional isolation material. This provides a direct access to the levitated sample and circumvents any influence of the climate unit material to the running analyses.

A wall-free climate unit for acoustic levitators

NASA Astrophysics Data System (ADS)

Schlegel, M. C.; Wenzel, K.-J.; Sarfraz, A.; Panne, U.; Emmerling, F.

2012-05-01

Acoustic levitation represents the physical background of trapping a sample in a standing acoustic wave with no contact to the wave generating device. For the last three decades, sample holders based on this effect have been commonly used for contact free handling of samples coupled with a number of analytical techniques. In this study, a wall-free climate unit is presented, which allows the control of the environmental conditions of suspended samples. The insulation is based on a continuous cold/hot gas flow around the sample and thus does not require any additional isolation material. This provides a direct access to the levitated sample and circumvents any influence of the climate unit material to the running analyses.

A comparison of dynamical and statistical downscaling methods for regional wave climate projections along French coastlines.

NASA Astrophysics Data System (ADS)

Laugel, Amélie; Menendez, Melisa; Benoit, Michel; Mattarolo, Giovanni; Mendez, Fernando

2013-04-01

Wave climate forecasting is a major issue for numerous marine and coastal related activities, such as offshore industries, flooding risks assessment and wave energy resource evaluation, among others. Generally, there are two main ways to predict the impacts of the climate change on the wave climate at regional scale: the dynamical and the statistical downscaling of GCM (Global Climate Model). In this study, both methods have been applied on the French coast (Atlantic , English Channel and North Sea shoreline) under three climate change scenarios (A1B, A2, B1) simulated with the GCM ARPEGE-CLIMAT, from Météo-France (AR4, IPCC). The aim of the work is to characterise the wave climatology of the 21st century and compare the statistical and dynamical methods pointing out advantages and disadvantages of each approach. The statistical downscaling method proposed by the Environmental Hydraulics Institute of Cantabria (Spain) has been applied (Menendez et al., 2011). At a particular location, the sea-state climate (Predictand Y) is defined as a function, Y=f(X), of several atmospheric circulation patterns (Predictor X). Assuming these climate associations between predictor and predictand are stationary, the statistical approach has been used to project the future wave conditions with reference to the GCM. The statistical relations between predictor and predictand have been established over 31 years, from 1979 to 2009. The predictor is built as the 3-days-averaged squared sea level pressure gradient from the hourly CFSR database (Climate Forecast System Reanalysis, http://cfs.ncep.noaa.gov/cfsr/). The predictand has been extracted from the 31-years hindcast sea-state database ANEMOC-2 performed with the 3G spectral wave model TOMAWAC (Benoit et al., 1996), developed at EDF R&D LNHE and Saint-Venant Laboratory for Hydraulics and forced by the CFSR 10m wind field. Significant wave height, peak period and mean wave direction have been extracted with an hourly-resolution at 110 coastal locations along the French coast. The model, based on the BAJ parameterization of the source terms (Bidlot et al, 2007) was calibrated against ten years of GlobWave altimeter observations (2000-2009) and validated through deep and shallow water buoy observations. The dynamical downscaling method has been performed with the same numerical wave model TOMAWAC used for building ANEMOC-2. Forecast simulations are forced by the 10m wind fields of ARPEGE-CLIMAT (A1B, A2, B1) from 2010 to 2100. The model covers the Atlantic Ocean and uses a spatial resolution along the French and European coast of 10 and 20 km respectively. The results of the model are stored with a time resolution of one hour. References: Benoit M., Marcos F., and F. Becq, (1996). Development of a third generation shallow-water wave model with unstructured spatial meshing. Proc. 25th Int. Conf. on Coastal Eng., (ICCE'1996), Orlando (Florida, USA), pp 465-478. Bidlot J-R, Janssen P. and Adballa S., (2007). A revised formulation of ocean wave dissipation and its model impact, technical memorandum ECMWF n°509. Menendez, M., Mendez, F.J., Izaguirre,C., Camus, P., Espejo, A., Canovas, V., Minguez, R., Losada, I.J., Medina, R. (2011). Statistical Downscaling of Multivariate Wave Climate Using a Weather Type Approach, 12th International Workshop on Wave Hindcasting and Forecasting and 3rd Coastal Hazard Symposium, Kona (Hawaii).

The Mediterranean surface wave climate inferred from future scenario simulations

NASA Astrophysics Data System (ADS)

Lionello, P.; Cogo, S.; Galati, M. B.; Sanna, A.

2008-09-01

This study is based on 30-year long simulations of the wind-wave field in the Mediterranean Sea carried out with the WAM model. Wave fields have been computed for the 2071-2100 period of the A2, B2 emission scenarios and for the 1961-1990 period of the present climate (REF). The wave model has been forced by the wind field computed by a regional climate model with 50 km resolution. The mean SWH (Significant Wave Height) field over large fraction of the Mediterranean sea is lower for the A2 scenario than for the present climate during winter, spring and autumn. During summer the A2 mean SWH field is also lower everywhere, except for two areas, those between Greece and Northern Africa and between Spain and Algeria, where it is significantly higher. All these changes are similar, though smaller and less significant, in the B2 scenario, except during winter in the north-western Mediterranean Sea, when the B2 mean SWH field is higher than in the REF simulation. Also extreme SWH values are smaller in future scenarios than in the present climate and such SWH change is larger for the A2 than for the B2 scenario. The only exception is the presence of higher SWH extremes in the central Mediterranean during summer for the A2 scenario. In general, changes of SWH, wind speed and atmospheric circulation are consistent, and results show milder marine storms in future scenarios than in the present climate.

Morphological Inheritance in Sandy Coastline Morphologies Subject to Long-Term Changes in Wave Climate: Surprising Insights from a Coastline Evolution Model

NASA Astrophysics Data System (ADS)

Murray, A. B.; Thomas, C.; Hurst, M. D.; Barkwith, A.; Ashton, A. D.; Ellis, M. A.

2014-12-01

Recent numerical modelling demonstrates that when sandy coastlines are affected predominantly by waves approaching from "high" angles (> ~45° between the coastline and wave crests at the offshore limit of shore-parallel contours), large-scale (kms to 100 kms) morphodynamic instabilities and finite-amplitude interactions can lead to the emergence of striking coastline features, including sand waves, capes and spits. The type of feature that emerges depends on the wave climate, defined as the angular distribution of wave influences on alongshore sediment transport. Under a constant wave climate, coastline morphology reaches a dynamical steady state; the cross-shore/alongshore aspect ratio and the general appearance of the features remains constant. In previous modelling involving wave-climate change, as well as comparisons between observed coastline morphologies and wave climates, it has been implicitly assumed that the morphology adjusts in a quasi-equilibrium fashion, so that at any time the coastline shape reflects the current forcing. However, here we present new model results showing pronounced path dependence in coastline morphodynamics. In experiments with a period of constant wave climate followed by a period of transition to a new wave climate and then a run-on phase, the features that exist during the run-on phase can be qualitatively and quantitatively different from those that would develop initially under the final wave climate. Although the features inherited from the past wave-climate history may in some case be true alternate stable states, in other cases the inherited features gradually decay toward the morphology that would be expected given the final wave climate. A suite of such experiments allows us to characterize how the e-folding timescale of this decay depends on 1) the initial wave climate, 2) the path through wave-climate space, and 3) the rate of transition. When the initial features are flying spits with cross-shore amplitudes of 6 - 8 km, e-folding times can be on the order of millennia or longer. These results could provide a new perspective when interpreting current and past coastline features. In addition, the complex paleo-coastline structure that develops in the coastal hinterlands in these experiments could be relevant to the structures observed in some coastal environments.

Impacts of climate changes on ocean surface gravity waves over the eastern Canadian shelf

NASA Astrophysics Data System (ADS)

Guo, Lanli; Sheng, Jinyu

2017-05-01

A numerical study is conducted to investigate the impact of climate changes on ocean surface gravity waves over the eastern Canadian shelf (ECS). The "business-as-usual" climate scenario known as Representative Concentration Pathway RCP8.5 is considered in this study. Changes in the ocean surface gravity waves over the study region for the period 1979-2100 are examined based on 3 hourly ocean waves simulated by the third-generation ocean wave model known as WAVEWATCHIII. The wave model is driven by surface winds and ice conditions produced by the Canadian Regional Climate Model (CanRCM4). The whole study period is divided into the present (1979-2008), near future (2021-2050) and far future (2071-2100) periods to quantify possible future changes of ocean waves over the ECS. In comparison with the present ocean wave conditions, the time-mean significant wave heights ( H s ) are expected to increase over most of the ECS in the near future and decrease over this region in the far future period. The time-means of the annual 5% largest H s are projected to increase over the ECS in both near and far future periods due mainly to the changes in surface winds. The future changes in the time-means of the annual 5% largest H s and 10-m wind speeds are projected to be twice as strong as the changes in annual means. An analysis of inverse wave ages suggests that the occurrence of wind seas is projected to increase over the southern Labrador and central Newfoundland Shelves in the near future period, and occurrence of swells is projected to increase over other areas of the ECS in both the near and far future periods.

Toward a Predictive Model of Arctic Coastal Retreat in a Warming Climate, Beaufort Sea, Alaska

DTIC Science & Technology

2011-09-30

level by waves and surge and tide. Melt rate is governed by an empirically based iceberg melting algorithm that includes explicitly the roles of wave...Thermal erosion of a permafrost coastline: Improving process-based models using time-lapse photography, Arctic Alpine Antarctic Research 43(3): 474

Statistical Downscaling in Multi-dimensional Wave Climate Forecast

NASA Astrophysics Data System (ADS)

Camus, P.; Méndez, F. J.; Medina, R.; Losada, I. J.; Cofiño, A. S.; Gutiérrez, J. M.

2009-04-01

Wave climate at a particular site is defined by the statistical distribution of sea state parameters, such as significant wave height, mean wave period, mean wave direction, wind velocity, wind direction and storm surge. Nowadays, long-term time series of these parameters are available from reanalysis databases obtained by numerical models. The Self-Organizing Map (SOM) technique is applied to characterize multi-dimensional wave climate, obtaining the relevant "wave types" spanning the historical variability. This technique summarizes multi-dimension of wave climate in terms of a set of clusters projected in low-dimensional lattice with a spatial organization, providing Probability Density Functions (PDFs) on the lattice. On the other hand, wind and storm surge depend on instantaneous local large-scale sea level pressure (SLP) fields while waves depend on the recent history of these fields (say, 1 to 5 days). Thus, these variables are associated with large-scale atmospheric circulation patterns. In this work, a nearest-neighbors analog method is used to predict monthly multi-dimensional wave climate. This method establishes relationships between the large-scale atmospheric circulation patterns from numerical models (SLP fields as predictors) with local wave databases of observations (monthly wave climate SOM PDFs as predictand) to set up statistical models. A wave reanalysis database, developed by Puertos del Estado (Ministerio de Fomento), is considered as historical time series of local variables. The simultaneous SLP fields calculated by NCEP atmospheric reanalysis are used as predictors. Several applications with different size of sea level pressure grid and with different temporal domain resolution are compared to obtain the optimal statistical model that better represents the monthly wave climate at a particular site. In this work we examine the potential skill of this downscaling approach considering perfect-model conditions, but we will also analyze the suitability of this methodology to be used for seasonal forecast and for long-term climate change scenario projection of wave climate.

Extreme storm surge and wind wave climate scenario simulations at the Venetian littoral

NASA Astrophysics Data System (ADS)

Lionello, P.; Galati, M. B.; Elvini, E.

Scenario climate projections for extreme marine storms producing storm surges and wind waves are very important for the northern flat coast of the Adriatic Sea, where the area at risk includes a unique cultural and environmental heritage, and important economic activities. This study uses a shallow water model and a spectral wave model for computing the storm surge and the wind wave field, respectively, from the sea level pressure and wind fields that have been computed by the RegCM regional climate model. Simulations cover the period 1961-1990 for the present climate (control simulations) and the period 2071-2100 for the A2 and B2 scenarios. Generalized Extreme Value analysis is used for estimating values for the 10 and 100 year return times. The adequacy of these modeling tools for a reliable estimation of the climate change signal, without needing further downscaling is shown. However, this study has mainly a methodological value, because issues such as interdecadal variability and intermodel variability cannot be addressed, since the analysis is based on single model 30-year long simulations. The control simulation looks reasonably accurate for extreme value analysis, though it overestimates/underestimates the frequency of high/low surge and wind wave events with respect to observations. Scenario simulations suggest higher frequency of intense storms for the B2 scenario, but not for the A2. Likely, these differences are not the effect of climate change, but of climate multidecadal variability. Extreme storms are stronger in future scenarios, but differences are not statistically significant. Therefore this study does not provide convincing evidence for more stormy conditions in future scenarios.

[Wave-type time series variation of the correlation between NDVI and climatic factors].

PubMed

Bi, Xiaoli; Wang, Hui; Ge, Jianping

2005-02-01

Based on the 1992-1996 data of 1 km monthly NDVI and those of the monthly precipitation and mean temperature collected by 400 standard meteorological stations in China, this paper analyzed the temporal and spatial dynamic changes of the correlation between NDVI and climatic factors in different climate districts of this country. The results showed that there was a significant correlation between monthly precipitations and NDVI. The wave-type time series model could simulate well the temporal dynamic changes of the correlation between NDVI and climatic factors, and the simulated results of the correlation between NDVI and precipitation was better than that between NDVI and temperature. The correlation coefficients (R2) were 0.91 and 0.86, respectively for the whole country.

Heat waves connect abrupt polar climate changes during the past 67ka: evidence from sediment core GeoB3912-1

NASA Astrophysics Data System (ADS)

Yang, X.; Rial, J. A.

2014-12-01

According to the hypothesis of polar synchronization, climate variations of Earth's poles are connected with a persistent phase lock of π/2 throughout the last glacial period. However, it is not clear yet how the Earth's two poles communicate with each other, the Thermohaline circulation (THC) being a possible candidate for signal carrier. Here we present a possible way of climate variation propagation through the Atlantic Ocean - likely in the form of heat or thermal wave (Cattaneo's solution) - based on lagged correlation between an organic carbon climate proxy record from the tropical Atlantic and the south-north polar temperature gradient. We further demonstrate that the speed of such propagation is frequency dependent, of which the wave of the longest period travels the fastest at the speed of ~32 km/year consistent with the estimated speed of the THC. The observed speed - frequency relationship can be successfully modeled as resulting from a propagating dispersive thermal wave initiated by the polar temperature gradient maximum. We show that such heat wave propagation is a potential mechanism to couple and synchronize the polar climates during the last glacial period and to force the occurrence of Heinrich events. To summarize, the polar temperature gradient anomalies are consequence of the π/2 phase lock between the polar climates, which is caused by polar synchronization maintained by the coupling, which is, as the data suggest, in the form of thermal waves. The spikes in organic carbon and the Fe/Ca ratio records in the core GeoB3912-1 can be thought of as snapshots of the passage of strong meteorological wavefronts through the equatorial region. The results strongly suggest that each peak in the organic carbon recorded a half-hemisphere-delayed passage of a wave-like disturbance through the equator carrying the south-north temperature gradient maxima. And each of these occurs within timing error of the Heinrich events H0-H6.

Heat waves measured with MODIS land surface temperature data predict changes in avian community structure

Treesearch

Thomas P. Albright; Anna M. Pidgeon; Chadwick D. Rittenhouse; Murray K. Clayton; Curtis H. Flather; Patrick D. Culbert; Volker C. Radeloff

2011-01-01

Heat waves are expected to become more frequent and severe as climate changes, with unknown consequences for biodiversity. We sought to identify ecologically-relevant broad-scale indicators of heat waves based on MODIS land surface temperature (LST) and interpolated air temperature data and assess their associations with avian community structure. Specifically, we...

Effects of Regional Climate Change on the Wave Conditions in the Western Baltic Sea

NASA Astrophysics Data System (ADS)

Dreier, N.; Fröhle, P.

2017-12-01

The local wave climate in the Western Baltic Sea is mainly generated by the local wind field over the area. Long-term changes of the local wind conditions that are induced e.g. by regional climate change, directly affect the local wave climate and other local wind driven coastal processes like e.g. the longshore sediment transport. The changes of the local wave climate play an important role for the safe functional and structural design of new, or the adaption of existing, coastal protection structures as well as for the assessment of long-term morphological changes of the coastline. In this study, the wave model SWAN is used for the calculation of hourly wave conditions in the Western Baltic Sea between 1960 and 2100. Future wind conditions from two regional climate models (Cosmo-CLM and REMO) that have been forced by different future greenhouse gas emission scenarios used within AR4 (A1B, B1) and AR5 (RCP4.5 and RCP8.5) of IPCC are used as input for the wave model. The changes of the average wave conditions are analyzed from comparisons between the 30 years averages for the future (e.g. 2071-2100) and the reference period 1971-2000. Regarding the emission scenarios A1B and B1, a significant change of the 30 years averages of significant wave height at westerly wind exposed locations with predominant higher values up to +10% is found (cf. Fig. 1). In contrast, the change of the 30 years averages of significant wave height is more weak at easterly wind exposed locations, resulting in higher and lower values between -5% to +5%. Moreover, more wave events from W-NW and fewer events from N-NE can be expected, due to changes of the frequency of occurrence of the 30 years averages of mean wave direction. The changes of extreme wave heights are analyzed based on methods of extreme value analysis and the time series of wave parameters at selected locations nearby the German Baltic Sea coast. No robust changes of the significant wave heights with a return period of 200 years are found for the emission scenarios A1B and B1. Both increases and decreases of the extreme wave heights are possible within a range of -18% to +18% (-0.5m to +0.5m). In the presentation, we will show results from the assessment of the changes of the wave conditions for the emission scenarios RCP4.5 and RCP8.5 and discuss possible impacts for the German Baltic Sea coast.

Wave climate, sediment supply and the depth of the sand-mud transition: A global survey

USGS Publications Warehouse

George, D.A.; Hill, P.S.

2008-01-01

The influences of wave climate and sediment supply on the depths of sand-mud transitions (hSMT) are investigated. Depths of sand-mud transitions (SMT) are based on published granulometric data from surface samples gathered from 14 sites in different wave-dominated coastal environments with fluvial input, including high energy (Columbia, Eel, Russian, San Lorenzo, Copper, and Nepean rivers), moderate energy (Ebro, Nile, Santa Clara, Tseng-wen and Kao-ping rivers), and low energy (Po, Pescara and Tronto rivers) regimes. Geometric mean diameter (GMD) and mud percent are compiled from samples along shore-normal transects, and significant correlation is found between these two textural descriptors. Nominally, the SMT is defined as the transition from GMD > 63????m to 25% mud. This dual definition is applied to the 14 systems, and hSMT is tabulated for each system. Correlation is found between hSMT and the depth at which wave-induced bottom shear stress equals the critical erosion shear stress of the largest mud particles and also between hSMT and significant wave height. Lack of correlation between hSMT and sediment load of nearby rivers indicates either that the influence of sediment supply on depth of the sand-mud transition is small or is not adequately represented in this study. Shelf width and slope do not correlate with residuals from a formalized linear relationship between hSMT and significant wave height. The relationship between hSMT and wave climate is useful for calibration of numerical models of erosion and deposition in wave-dominated coastal environments, for prediction of seabed properties in remote or inaccessible areas, and for reconstruction of paleodepth based on facies changes from sand to mud in ancient rocks. ?? 2008.

Controls of multi-modal wave conditions in a complex coastal setting

USGS Publications Warehouse

Hegermiller, Christie; Rueda, Ana C.; Erikson, Li H.; Barnard, Patrick L.; Antolinez, J.A.A.; Mendez, Fernando J.

2017-01-01

Coastal hazards emerge from the combined effect of wave conditions and sea level anomalies associated with storms or low-frequency atmosphere-ocean oscillations. Rigorous characterization of wave climate is limited by the availability of spectral wave observations, the computational cost of dynamical simulations, and the ability to link wave-generating atmospheric patterns with coastal conditions. We present a hybrid statistical-dynamical approach to simulating nearshore wave climate in complex coastal settings, demonstrated in the Southern California Bight, where waves arriving from distant, disparate locations are refracted over complex bathymetry and shadowed by offshore islands. Contributions of wave families and large-scale atmospheric drivers to nearshore wave energy flux are analyzed. Results highlight the variability of influences controlling wave conditions along neighboring coastlines. The universal method demonstrated here can be applied to complex coastal settings worldwide, facilitating analysis of the effects of climate change on nearshore wave climate.

Controls of Multimodal Wave Conditions in a Complex Coastal Setting

NASA Astrophysics Data System (ADS)

Hegermiller, C. A.; Rueda, A.; Erikson, L. H.; Barnard, P. L.; Antolinez, J. A. A.; Mendez, F. J.

2017-12-01

Coastal hazards emerge from the combined effect of wave conditions and sea level anomalies associated with storms or low-frequency atmosphere-ocean oscillations. Rigorous characterization of wave climate is limited by the availability of spectral wave observations, the computational cost of dynamical simulations, and the ability to link wave-generating atmospheric patterns with coastal conditions. We present a hybrid statistical-dynamical approach to simulating nearshore wave climate in complex coastal settings, demonstrated in the Southern California Bight, where waves arriving from distant, disparate locations are refracted over complex bathymetry and shadowed by offshore islands. Contributions of wave families and large-scale atmospheric drivers to nearshore wave energy flux are analyzed. Results highlight the variability of influences controlling wave conditions along neighboring coastlines. The universal method demonstrated here can be applied to complex coastal settings worldwide, facilitating analysis of the effects of climate change on nearshore wave climate.

Climate of migration? How climate triggered migration from southwest Germany to North America during the 19th century

NASA Astrophysics Data System (ADS)

Glaser, Rüdiger; Himmelsbach, Iso; Bösmeier, Annette

2017-11-01

This paper contributes to the ongoing debate on the extent to which climate and climatic change can have a negative impact on societies by triggering migration, or even contribute to conflict. It summarizes results from the transdisciplinary project Climate of migration (funded 2010-2014), whose innovative title was created by Franz Mauelshagen and Uwe Lübken. The overall goal of this project was to analyze the relation between climatic and socioeconomic parameters and major migration waves from southwest Germany to North America during the 19th century. The article assesses the extent to which climatic conditions triggered these migration waves. The century investigated was in general characterized by the Little Ice Age with three distinct cooling periods, causing major glacier advances in the alpine regions and numerous climatic extremes such as major floods, droughts and severe winter. Societal changes were tremendous, marked by the warfare during the Napoleonic era (until 1815), the abolition of serfdom (1817), the bourgeois revolution (1847/48), economic freedom (1862), the beginning of industrialization accompanied by large-scale rural-urban migration resulting in urban poverty, and finally by the foundation of the German Empire in 1871.

The presented study is based on quantitative data and a qualitative, information-based discourse analysis. It considers climatic conditions as well as socioeconomic and political issues, leading to the hypothesis of a chain of effects ranging from unfavorable climatic conditions to a decrease in crop yields to rising cereal prices and finally to emigration. These circumstances were investigated extensively for the peak emigration years identified with each migration wave. Furthermore, the long-term relations between emigration and the prevailing climatic conditions, crop yields and cereal prices were statistically evaluated with a sequence of linear models which were significant with explanatory power between 22 and 38 %.

Wave Climate and Wave Mixing in the Marginal Ice Zones of Arctic Seas, Observations and Modelling

DTIC Science & Technology

2015-09-30

ababanin.com/ LONG-TERM GOALS The long-term goals of the present project are two: wind/wave climatology for the Arctic Seas, and their current...OBJECTIVES The wind/wave climatology for the Arctic Seas will be developed based on altimeter observations. It will have a major scientific and...applied significance as presently there is no reference climatology for this region of the ocean available. The new versions of wave models for the

Modelling the Holderness coast, eastern England: Past, present and future

NASA Astrophysics Data System (ADS)

Barkwith, A.; Limber, P. W.; Thomas, C. W.; Murray, A.; Jordan, H. M.; Ellis, M. A.

2012-12-01

The Holderness coast of eastern Yorkshire, England, is the most rapidly eroding coastline in Europe. Erosion can locally exceed 10 m in a single year and rates average 0.5 to 3 m yr-1, generally increasing from north to south. Pinned in the north by a chalk headland, the soft till coastline has a characteristic open spiral form terminated by a spit to the south. Erosion currently threatens local communities and infrastructure, including nationally important gas installations. Interventions to restrict local erosion usually result in enhanced erosion in adjacent, unprotected sections of coast, mirroring morphology seen on the large scale. We have initiated a modelling study to investigate the key controls on the form and evolution of this coastline, and its response to climate change, building on the Coastline Evolution Model (CEM) developed at Duke University, NC. We have adapted the CEM to permit an ensemble of simulations to be undertaken, based upon modified offshore wave climates, initial conditions and forcing factors. The CEM follows a standard 1d approach, where the cross-shore is collapsed into a single data point, allowing the planform shoreline shape and dynamics to be simulated. The model facilitates study of a coast with variable erosion rates, and enables simulation of coastline evolution when sediment is supplied from an eroding shoreface. Additionally, the CEM is adapted to use an observed two year, offshore wave climate data set as input. Initial work focussed on reconstruction of current coastline shape from an ensemble of hypothetical early Holocene shoreface positions and past wave climates. First order reconstruction of shoreline shape was achieved using several differing initial conditions and wave climates. For the majority of successful simulations, a steady state was noted for proceeding years, where erosion proceeds at an equal rate along the length of the coast south of the headland. Together with a sensitivity analysis, the derivation of the current coastline provided initial conditions for the second phase of the work: simulating the morphological response of the Holderness coastline to possible future changes in climate over the next century. An ensemble of future possible wave climate perturbations was generated from predictions of the likely response of the North Sea to future climate change over the next century, and applied linearly to the observed wave climate as each simulation progressed. The ensemble output was compared to a baseline simulation, run for a century under current wave climate, to assess the impact of predicted future climate on coastal erosion. Although this study does not currently take into account the changes in storm frequency, rises in sea level or the anthropogenic inputs that could influence the results, the initial output indicates erosional rates over the next century are likely to be retarded for the Holderness coastline under a changing climate.

Forecasting European cold waves based on subsampling strategies of CMIP5 and Euro-CORDEX ensembles

NASA Astrophysics Data System (ADS)

Cordero-Llana, Laura; Braconnot, Pascale; Vautard, Robert; Vrac, Mathieu; Jezequel, Aglae

2016-04-01

Forecasting future extreme events under the present changing climate represents a difficult task. Currently there are a large number of ensembles of simulations for climate projections that take in account different models and scenarios. However, there is a need for reducing the size of the ensemble to make the interpretation of these simulations more manageable for impact studies or climate risk assessment. This can be achieved by developing subsampling strategies to identify a limited number of simulations that best represent the ensemble. In this study, cold waves are chosen to test different approaches for subsampling available simulations. The definition of cold waves depends on the criteria used, but they are generally defined using a minimum temperature threshold, the duration of the cold spell as well as their geographical extend. These climate indicators are not universal, highlighting the difficulty of directly comparing different studies. As part of the of the CLIPC European project, we use daily surface temperature data obtained from CMIP5 outputs as well as Euro-CORDEX simulations to predict future cold waves events in Europe. From these simulations a clustering method is applied to minimise the number of ensembles required. Furthermore, we analyse the different uncertainties that arise from the different model characteristics and definitions of climate indicators. Finally, we will test if the same subsampling strategy can be used for different climate indicators. This will facilitate the use of the subsampling results for a wide number of impact assessment studies.

Future Heat Waves In Asia

NASA Astrophysics Data System (ADS)

Eltahir, E. A. B.

2017-12-01

I will review recent work from my group on the impact of climate change on the intensity and frequency of heat waves in Asia. Our studies covered Southwest Asia, South Asia, East China, and the Maritime continent. In any of these regions, the risk associated with climate change impact reflects intensity of natural hazard and level of human vulnerability. Previous work has shown that the wet-bulb temperature is a useful variable to consider in describing the natural hazard from heat waves since it can be easily compared to the natural threshold that defines the upper limit on human survivability. Based on an ensemble of high resolution climate change simulations, we project extremes of wet-bulb temperature conditions in each of these four regions of Asia. We consider the business-as-usual scenario of future greenhouse gas emissions, as well as a moderate mitigation scenario. The results from these regions will be compared and lessons learned summarized.

Projected Changes on the Global Surface Wave Drift Climate towards the END of the Twenty-First Century

NASA Astrophysics Data System (ADS)

Carrasco, Ana; Semedo, Alvaro; Behrens, Arno; Weisse, Ralf; Breivik, Øyvind; Saetra, Øyvind; Håkon Christensen, Kai

2016-04-01

The global wave-induced current (the Stokes Drift - SD) is an important feature of the ocean surface, with mean values close to 10 cm/s along the extra-tropical storm tracks in both hemispheres. Besides the horizontal displacement of large volumes of water the SD also plays an important role in the ocean mix-layer turbulence structure, particularly in stormy or high wind speed areas. The role of the wave-induced currents in the ocean mix-layer and in the sea surface temperature (SST) is currently a hot topic of air-sea interaction research, from forecast to climate ranges. The SD is mostly driven by wind sea waves and highly sensitive to changes in the overlaying wind speed and direction. The impact of climate change in the global wave-induced current climate will be presented. The wave model WAM has been forced by the global climate model (GCM) ECHAM5 wind speed (at 10 m height) and ice, for present-day and potential future climate conditions towards the end of the end of the twenty-first century, represented by the Intergovernmental Panel for Climate Change (IPCC) CMIP3 (Coupled Model Inter-comparison Project phase 3) A1B greenhouse gas emission scenario (usually referred to as a ''medium-high emissions'' scenario). Several wave parameters were stored as output in the WAM model simulations, including the wave spectra. The 6 hourly and 0.5°×0.5°, temporal and space resolution, wave spectra were used to compute the SD global climate of two 32-yr periods, representative of the end of the twentieth (1959-1990) and twenty-first (1969-2100) centuries. Comparisons of the present climate run with the ECMWF (European Centre for Medium-Range Weather Forecasts) ERA-40 reanalysis are used to assess the capability of the WAM-ECHAM5 runs to produce realistic SD results. This study is part of the WRCP-JCOMM COWCLIP (Coordinated Ocean Wave Climate Project) effort.

A Bayesian-Based System to Assess Wave-Driven Flooding Hazards on Coral Reef-Lined Coasts

NASA Astrophysics Data System (ADS)

Pearson, S. G.; Storlazzi, C. D.; van Dongeren, A. R.; Tissier, M. F. S.; Reniers, A. J. H. M.

2017-12-01

Many low-elevation, coral reef-lined, tropical coasts are vulnerable to the effects of climate change, sea level rise, and wave-induced flooding. The considerable morphological diversity of these coasts and the variability of the hydrodynamic forcing that they are exposed to make predicting wave-induced flooding a challenge. A process-based wave-resolving hydrodynamic model (XBeach Non-Hydrostatic, "XBNH") was used to create a large synthetic database for use in a "Bayesian Estimator for Wave Attack in Reef Environments" (BEWARE), relating incident hydrodynamics and coral reef geomorphology to coastal flooding hazards on reef-lined coasts. Building on previous work, BEWARE improves system understanding of reef hydrodynamics by examining the intrinsic reef and extrinsic forcing factors controlling runup and flooding on reef-lined coasts. The Bayesian estimator has high predictive skill for the XBNH model outputs that are flooding indicators, and was validated for a number of available field cases. It was found that, in order to accurately predict flooding hazards, water depth over the reef flat, incident wave conditions, and reef flat width are the most essential factors, whereas other factors such as beach slope and bed friction due to the presence or absence of corals are less important. BEWARE is a potentially powerful tool for use in early warning systems or risk assessment studies, and can be used to make projections about how wave-induced flooding on coral reef-lined coasts may change due to climate change.