Multiscale flood risk assessment under climate change: the case of the Miño river in the city of Ourense, Spain

[Abstract:] River floods, which are one of the most dangerous natural hazards worldwide, have increased in intensity and frequency in recent decades as a result of climate change, and the future scenario is expected to be even worse. Therefore, their knowledge, predictability, and mitigation represent a key challenge for the scientific community in the coming decades, especially in those local areas that are most vulnerable to these extreme events. In this sense, a multiscale analysis is essential to obtain detailed maps of the future evolution of floods. In the multiscale analysis, the historical and future precipitation data from the CORDEX (Coordinated Regional Downscaling Experiment) project are used as input in a hydrological model (HEC-HMS) which, in turn, feeds a 2D hydraulic model (Iber+). This integration allows knowing the projected future changes in the flow pattern of the river, as well as analyzing the impact of floods in vulnerable areas through the flood hazard maps obtained with hydraulic simulations. The multiscale analysis is applied to the case of the Miño-Sil basin (NW Spain), specifically to the city of Ourense. The results show a delay in the flood season and an increase in the frequency and intensity of extreme river flows in the Miño-Sil basin, which will cause more situations of flooding in many areas frequented by pedestrians and in important infrastructure of the city of Ourense. In addition, an increase in water depths associated with future floods was also detected, confirming the trend for future floods to be not only more frequent but also more intense. Detailed maps of the future evolution of floods also provide key information to decision-makers to take effective measures in advance in those areas most vulnerable to flooding in the coming decades. Although the methodology presented is applied to a particular area, its strength lies in the fact that its implementation in other basins and cities is simple, also taking into account that all the models used are freely accessible.Xunta de Galicia; ED431C 2021/44FEDER; 0034_RISC_ML_6_EXunta de Galicia; ED481B-2021-10

NW Iberian Peninsula coastal upwelling future weakening: competition between wind intensification and surface heating

Climate change will modify the oceanographic future properties of the NW Iberian Peninsula due to the projected variations in the meteorological forcing, that will intensify local winds and promote surface heating. The Delft3D-Flow model forced with atmospheric conditions provided within the framework of the CORDEX project under the RCP 8.5 greenhouse emission scenario was used to analyse changes in upwelling. Numerical experiments were conducted under high-extreme upwelling conditions for the historical (1976-2005) and future (2070-2099) period. This study also innovates through the exploitation of a numerical modelling approach that includes both shelf and estuarine processes along the coastal zone. Coastal upwelling will be less effective in the future despite the enhancement of upwelling favorable wind patterns previously predicted for this region. Upwelling weakening is due to the future sea surface warming that will increase the stratification of the upper layers hindering the upward displacement of the underlying water, reducing the surface input of nutrients.publishe

Economic Feasibility of Floating Offshore Wind Farms Considering Near Future Wind Resources: Case Study of Iberian Coast and Bay of Biscay

[Abstract] Wind energy resources are subject to changes in climate, so the use of wind energy density projections in the near future is essential to determine the viability and profitability of wind farms at particular locations. Thus, a step forward in determining the economic assessment of floating offshore wind farms was taken by considering current and near-future wind energy resources in assessing the main parameters that determine the economic viability (net present value, internal rate of return, and levelized cost of energy) of wind farms. This study was carried out along the Atlantic coast from Brest to Cape St. Vincent. Results show that the future reduction in wind energy density (2%–6%) mainly affects the net present value (NPV) of the farm and has little influence on the levelized cost of energy (LCOE). This study provides a good estimate of the economic viability of OWFs (Offshore Wind Farms) by taking into account how wind resources can vary due to climate change over the lifetime of the farm.Ministerio de Ciencia e Innovación; 10.13039/501100011033.Xunta de Galicia; ED431C 2017/6

Hydrography of the Pontevedra Ria: Intra-annual spatial and temporal variability in a Galician coastal system (NW Spain)

In order to ameliorate the dearth of existing scientific knowledge concerning the hydrography of the Pontevedra Ria, a systematic investigation was carried out between October 1997-98. Salinity variations were closely related to river discharge whereas bottom waters presented oceanic characteristics over the whole year. Current was controlled by tide, river discharge, and wind in the internal ria where the highest velocities were directed along the ria channel with a low transverse component. Favorable atmospheric conditions in spring induced coastal upwelling up the continental shelf. In May the upwelling was sufficiently strong to be detected in the inner ria and intensified in July and August, cooling the ria water to 12 degrees -14 degreesC. Upwelling ceased in September, and from November to March seawater transported by the poleward current (35.9; 15 degreesC) was detected on the shelf. From January until March, unanticipated favorable upwelling conditions provoked an influx of poleward inside the ria. Ria intrusion of poleward water and association with occasional winter upwelling conditions has not been observed previously. Isopycnic three-dimensional (3-D) surface and 2-D isopycnal maps show that with high river runoff or intense upwelling, lower-salinity water leaves the ria near the northern margin in the surface layer. Under negative upwelling conditions, the water is partially dammed inside the ria and exits the ria when the wind speed falls. During upwelling events, ENACW penetrated the ria, especially near the southern shore. Arrival of ENACW at the northern entrance impedes the outward water flow through this mouth

Variability of coastal and ocean water temperature in the upper 700 m along the western Iberian Peninsula from 1975 to 2006

Temperature is observed to have different trends at coastal and ocean locations along the western Iberian Peninsula from 1975 to 2006, which corresponds to the last warming period in the area under study. The analysis was carried out by means of the Simple Ocean Data Assimilation (SODA). Reanalysis data are available at monthly scale with a horizontal resolution of 0.5° × 0.5° and a vertical resolution of 40 levels, which allows obtaining information beneath the sea surface. Only the first 21 vertical levels (from 5.0 m to 729.35 m) were considered here, since the most important changes in heat content observed for the world ocean during the last decades, correspond to the upper 700 m. Warming was observed to be considerably higher at ocean locations than at coastal ones. Ocean warming ranged from values on the order of 0.3 °C dec(-1) near surface to less than 0.1 °C dec(-1) at 500 m, while coastal warming showed values close to 0.2 °C dec(-1) near surface, decreasing rapidly below 0.1 °C dec(-1) for depths on the order of 50 m. The heat content anomaly for the upper 700 m, showed a sharp increase from coast (0.46 Wm(-2)) to ocean (1.59 Wm(-2)). The difference between coastal and ocean values was related to the presence of coastal upwelling, which partially inhibits the warming from surface of near shore water.publishe

Recent Shift in Climate Relationship Enables Prediction of the Timing of Bird Breeding

Large-scale climate processes influence many aspects of ecology including breeding phenology, reproductive success and survival across a wide range of taxa. Some effects are direct, for example, in temperate-zone birds, ambient temperature is an important cue enabling breeding effort to coincide with maximum food availability, and earlier breeding in response to warmer springs has been documented in many species. In other cases, time-lags of up to several years in ecological responses have been reported, with effects mediated through biotic mechanisms such as growth rates or abundance of food supplies. Here we use 23 years of data for a temperate woodland bird species, the great tit (Parus major), breeding in deciduous woodland in eastern England to demonstrate a time-lagged linear relationship between the on-set of egg laying and the winter index of the North Atlantic Oscillation such that timing can be predicted from the winter index for the previous year. Thus the timing of bird breeding (and, by inference, the timing of spring events in general) can be predicted one year in advance. We also show that the relationship with the winter index appears to arise through an abiotic time-lag with local spring warmth in our study area. Examining this link between local conditions and larger-scale processes in the longer-term showed that, in the past, significant relationships with the immediately preceding winter index were more common than those with the time-lagged index, and especially so from the late 1930s to the early 1970s. However, from the mid 1970s onwards, the time-lagged relationship has become the most significant, suggesting a recent change in climate patterns. The strength of the current time-lagged relationship suggests that it might have relevance for other temperature-dependent ecological relationships

Comparison of different wind products and buoy wind data with seasonality and interannual climate variability in the southern Bay of Biscay (2000-2009)

Ocean surface winds are essential factors in determining oceanographic and atmospheric processes that can affect ocean circulation and wave generation. Accurate surface wind datasets are needed, therefore, to enable the proper analysis of these processes. Wind data from six databases (National Centers for Environmental Prediction reanalysis (NCEP Reanalysis II), European Centre for Medium-Range Weather Forecasts (ECMWF) re-analysis (ERA-Interim), Modern-Era Retrospective-analysis for Research and Applications (MERRA), NCEP Climate Forecast System Reanalysis (CFSR), QuikSCAT and Cross-Calibrated Multi-Platform (CCMP)) were compared with wind measured in situ by four ocean buoys at the southern limit of the Bay of Biscay. The study covered the period 2000-2009 in such a way that the extent of the time series reduced the margin of error and allowed the disaggregation of the wind data using velocity bins and direction sectors. Statistical results confirmed that datasets with finer spatial resolution (lower than 0.5°×0.5°) gave better results, especially in near-shore areas. A more complete analysis was, therefore, carried out using the finer resolution datasets (QuikSCAT, CCMP and CFSR). This comparison showed that all the datasets were less accurate at low wind speeds (<4ms-1) and more accurate at moderate wind speeds. The calculated mean wind speed errors were similar for the three datasets, and the lowest value (1.67ms-1) was from the CCMP dataset. The lowest mean error for wind direction (~37°) was also observed in the CCMP data. The lowest mean wind speed (and direction) bias was obtained from the QuikSCAT data, and the next lowest from the CFSR data. The seasonality for north and east wind components was also determined for the last decade and the results were consistent with forcing for the continental slope current seasonality and winter temperatures or Navidad by wind stress. Correlations between NAO and north and east wind components were low showing that NAO could not be used as a proxy for local wind stress in the southern Bay of Biscay

Influence of the Barrie de la Maza dock on the circulation pattern of the Ría of a Coruña (NW-Spain)

A 3D hydrodynamical model is applied to the ria of A Coruña to analyze the evolution of the circulation pattern in the ria after the building of a breakwater (Barrie de la Maza dock) in the sixties. This circulation pattern has changed greatly. On the one hand, the circulation, which was almost parallel to the shore line under the original conditions, now shows a gyre near the end of the dock. On the other hand, a considerable increase (about 30%) in the velocities near the end of the breakwater and in the main channel of the estuary has been observed after the building of the dock. A stronger bottom shear stress has been generated in the estuary areas where the velocity increased. The bottom shear stress increase was particularly great (over 100%) near the end of the dock. This increase in the shear stress produced bottom erosion and matter resuspension, and consequently major changes in the bathymetry. In addition, in situ sedimentary measurements carried out by Lopez-Jamar (1996) corroborate the bottom erosion in the main chanel of the estuary and at the end of the dock produced by the velocity increase generated by the building of the breakwater

Trend values of mixed layer depth.

<p>(a) (b) Annual maxima trends and (c) (d) winter anomalies trends (m dec⁻¹) of PLD (left) and TLD (right) in the Bay of Biscay for the period 1975–2010. Black dots represent points with a significance level higher than 90%.</p

Correlations between annual maxima and winter anomalies of PLD/TLD calculated from ARGO and SODA databases for the period 2003–2010.

<p>Threshold values of ΔT = 0.5°C and Δσ_θ = 0.125 kg/m³ were used for potential temperature and for potential density, respectively. Statistical significance (p value) is showed in brackets.</p