Ocean model resolution dependence of Caribbean sea-level projections

Abstract Sea-level rise poses severe threats to coastal and low-lying regions around the world, by exacerbating coastal erosion and flooding. Adequate sea-level projections over the next decades are important for both decision making and for the development of successful adaptation strategies in these coastal and low-lying regions to climate change. Ocean components of climate models used in the most recent sea-level projections do not explicitly resolve ocean mesoscale processes. Only a few effects of these mesoscale processes are represented in these models, which leads to errors in the simulated properties of the ocean circulation that affect sea-level projections. Using the Caribbean Sea as an example region, we demonstrate a strong dependence of future sea-level change on ocean model resolution in simulations with a global climate model. The results indicate that, at least for the Caribbean Sea, adequate regional projections of sea-level change can only be obtained with ocean models which capture mesoscale processes.info:eu-repo/semantics/publishe

Water motion and vegetation control the pH dynamics in seagrass-dominated bays

info:eu-repo/semantics/publishe

Sea-level change in the Dutch Wadden Sea

Rising sea levels due to climate change can have severe consequences for coastal populations and ecosystems all around the world. Understanding and projecting sea-level rise is especially important for low-lying countries such as the Netherlands. It is of specific interest for vulnerable ecological and morphodynamic regions, such as the Wadden Sea UNESCO World Heritage region. Here we provide an overview of sea-level projections for the 21st century for the Wadden Sea region and a condensed review of the scientific data, understanding and uncertainties underpinning the projections. The sea-level projections are formulated in the framework of the geological history of the Wadden Sea region and are based on the regional sea-level projections published in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5). These IPCC AR5 projections are compared against updates derived from more recent literature and evaluated for the Wadden Sea region. The projections are further put into perspective by including interannual variability based on long-term tide-gauge records from observing stations at Den Helder and Delfzijl. We consider three climate scenarios, following the Representative Concentration Pathways (RCPs), as defined in IPCC AR5: the RCP2.6 scenario assumes that greenhouse gas (GHG) emissions decline after 2020; the RCP4.5 scenario assumes that GHG emissions peak at 2040 and decline thereafter; and the RCP8.5 scenario represents a continued rise of GHG emissions throughout the 21st century. For RCP8.5, we also evaluate several scenarios from recent literature where the mass loss in Antarctica accelerates at rates exceeding those presented in IPCC AR5. For the Dutch Wadden Sea, the IPCC AR5-based projected sea-level rise is 0.07±0.06m for the RCP4.5 scenario for the period 2018–30 (uncertainties representing 5–95%), with the RCP2.6 and RCP8.5 scenarios projecting 0.01m less and more, respectively. The projected rates of sea-level change in 2030 range between 2.6mma−1 for the 5th percentile of the RCP2.6 scenario to 9.1mma−1 for the 95th percentile of the RCP8.5 scenario. For the period 2018–50, the differences between the scenarios increase, with projected changes of 0.16±0.12m for RCP2.6, 0.19±0.11m for RCP4.5 and 0.23±0.12m for RCP8.5. The accompanying rates of change range between 2.3 and 12.4mma−1 in 2050. The differences between the scenarios amplify for the 2018–2100 period, with projected total changes of 0.41±0.25m for RCP2.6, 0.52±0.27m for RCP4.5 and 0.76±0.36m for RCP8.5. The projections for the RCP8.5 scenario are larger than the high-end projections presented in the 2008 Delta Commission Report (0.74m for 1990–2100) when the differences in time period are considered. The sea-level change rates range from 2.2 to 18.3mma−1 for the year 2100. We also assess the effect of accelerated ice mass loss on the sea-level projections under the RCP8.5 scenario, as recent literature suggests that there may be a larger contribution from Antarctica than presented in IPCC AR5 (potentially exceeding 1m in 2100). Changes in episodic extreme events, such as storm surges, and periodic (tidal) contributions on (sub-)daily timescales, have not been included in these sea-level projections. However, the potential impacts of these processes on sea-level change rates have been assessed in the report

Measuring and modeling the effect of surface moisture on the spectral reflectance of coastal beach sand

Surface moisture is an important supply limiting factor for aeolian sand transport, which is the primary driver of coastal dune development. As such, it is critical to account for the control of surface moisture on available sand for dune building. Optical remote sensing has the potential to measure surface moisture at a high spatio-temporal resolution. It is based on the principle that wet sand appears darker than dry sand: it is less reflective. The goals of this study are (1) to measure and model reflectance under controlled laboratory conditions as function of wavelength () and surface moisture () over the optical domain of 350–2500 nm, and (2) to explore the implications of our laboratory findings for accurately mapping the distribution of surface moisture under natural conditions. A laboratory spectroscopy experiment was conducted to measure spectral reflectance (1 nm interval) under different surface moisture conditions using beach sand. A non-linear increase of reflectance upon drying was observed over the full range of wavelengths. Two models were developed and tested. The first model is grounded in optics and describes the proportional contribution of scattering and absorption of light by pore water in an unsaturated sand matrix. The second model is grounded in soil physics and links the hydraulic behaviour of pore water in an unsaturated sand matrix to its optical properties. The optical model performed well for volumetric moisture content 24% ( 0.97), but underestimated reflectance for between 24–30% ( 0.92), most notable around the 1940 nm water absorption peak. The soil-physical model performed very well ( 0.99) but is limited to 4% 24%. Results from a field experiment show that a short-wave infrared terrestrial laser scanner ( = 1550 nm) can accurately relate surface moisture to reflectance (standard error 2.6%), demonstrating its potential to derive spatially extensive surface moisture maps of a natural coastal beach

The impact of upwelling on the intensification of anticyclonic ocean eddies in the Caribbean Sea

The mesoscale variability in the Caribbean Sea is dominated by anticyclonic eddies that are formed in the eastern part of the basin. These anticyclones intensify on their path westward while they pass the coastal upwelling region along the Venezuelan and Colombian coast. In this study, we used a regional model to show that this westward intensification of Caribbean anticyclones is steered by the advection of cold upwelling filaments. Following the thermal wind balance, the increased horizontal density gradients result in an increase in the vertical shear of the anticyclones and in their westward intensification. To assess the impact of variations in upwelling on the anticyclones, several simulations were performed in which the northward Ekman transport (and thus the upwelling strength) is altered. As expected, stronger (weaker) upwelling is associated with stronger (weaker) offshore cooling and a stronger (weaker) westward intensification of the anticyclones. Moreover, the simulations with weaker upwelling show farther advection of the Amazon and Orinoco River plumes into the basin. As a result, in these simulations the horizontal density gradients were predominantly set by horizontal salinity gradients. The importance of the horizontal density gradients driven by temperature, which are associated with the upwelling, increased with increasing upwelling strength. The results of this study highlight that both upwelling and the advection of the river plumes affect the life cycle of mesoscale eddies in the Caribbean Sea

Impacts of Tropical Cyclones on the Caribbean Under Future Climate Conditions

Joint effects of the dynamic sea-level rise projected changes in the large-scale atmosphere/ocean circulation, and wave climate on hurricane-induced extreme water levels in the Caribbean region are assessed. We use the 2D-depth integrated ADCIRC + SWAN wave-ocean model, baroclinically coupled to an ocean-eddying version of the Community Earth System Model, to compare impacts of the September 2017 hurricanes with projected impacts of similar hypothetical tropical storms occurring in the future. The model predicts only minor changes in the hurricane-induced extreme water levels for those Caribbean islands which were severely devastated by the 2017 tropical storms (Irma and Maria). That is, provided that the hurricane intensity remains at the present-day level, the global mean sea-level rise is the main future coastal flood risk factor

Ocean model resolution dependence of Caribbean sea-level projections

Sea-level rise poses severe threats to coastal and low-lying regions around the world, by exacerbating coastal erosion and flooding. Adequate sea-level projections over the next decades are important for both decision making and for the development of successful adaptation strategies in these coastal and low-lying regions to climate change. Ocean components of climate models used in the most recent sea-level projections do not explicitly resolve ocean mesoscale processes. Only a few effects of these mesoscale processes are represented in these models, which leads to errors in the simulated properties of the ocean circulation that affect sea-level projections. Using the Caribbean Sea as an example region, we demonstrate a strong dependence of future sea-level change on ocean model resolution in simulations with a global climate model. The results indicate that, at least for the Caribbean Sea, adequate regional projections of sea-level change can only be obtained with ocean models which capture mesoscale processes

Tide-surge, tide and surge simulations output of 2D DCSM-FM v7 from 1980 to 2020 at Euro platform.

This dataset includes results of hydrodynamic simulations for Euro platform, an offshore structure located in the southern North Sea that serves as a beacon for shipping and a measurement platform for the location. The results were generated with the 2D Dutch Continental Shelf Model - Flexible Mesh (DCSM, [Zijl and Groenenboom, 2019]), the successor of the version in Zijl et al. [2013,2015]. The model describes the tide-surge water level variability for the northwest European continental shelf between 15◦W to 13◦E and 43◦N to 64◦N by solving the depth-integrated shallow-water equations for hydrodynamic modeling of free-surface flows [Leendertse, 1967, Stelling, 1984]. Water level conditions are applied at the northern, western, and southern open boundaries. When modeling the tide-surge water levels, they are composed of the sum of the astronomical water levels and the surge. The tides are obtained from a harmonic expansion of 32 tidal constituents retrieved from the global ocean tide model FES2012 [Carr`ere et al., 2013] supplemented with the solar annual Sa constituent obtained from an earlier version of the model. The surge at the open boundaries is approximated by the time- and space-dependent inverse barometer correction. A smaller part of the tides is generated from the tidal potential within the model domain. When included, time- and space-varying atmospheric wind and pressure forcings are obtained from the ECMWF’s ERA5 reanalysis dataset [Hersbach et al., 2020]. In our simulations, we force the model by i) both tidal and meteorological (i.e., atmospheric wind and pressure) forcing, ii) tidal forcing only, and iii) meteorological forcing only. This enumeration also relates to the files included and described below.  The files included are:  i. 2D_DCSM-FM_A03_FES2014_GTSM_H1H2_1980-2020_EURPFM_complete.pkl ii. 2D_DCSM-FM_A03_FES2014_GTSM_H1H2_1980-2020_astro_EURPFM_complete.pkl iii. 2D_DCSM-FM_A03_FES2014_GTSM_H1H2_1980-2020_noTide_noTGF_EURPFM_complete.pkl References: F. Zijl and J. Groenenboom. Development of a sixth-generation model for the NW European Shelf (DCSM-FM 0.5nm). Technical report, Deltares, 2019. Available online at: https: //publications.deltares.nl/11203715_004.pdf (accessed July 18, 2022). F. Zijl, M. Verlaan, and H. Gerritsen. Improved water-level forecasting for the northwest european shelf and north sea through direct modeling of tide, surge and non-linear interaction. Ocean Dynam., 63(7):823–847, 2013. ISSN 1616-7228. doi: 10.1007/s10236-013-0624-2. F. Zijl, J. Sumihar, and M. Verlaan. Application of data assimilation for improved operational water level forecasting on the northwest European shelf and north sea. Ocean Dynam., 65(12): 1699–1716, 2015. ISSN 1616-7228. doi: 10.1007/s10236-015-0898-7. L. Carr`ere, F. Lyard, M. Cancet, A. Guillot, and L. Roblou. FES2012: A New Global Tidal Model Taking Advantage of Nearly 20 Years of Altimetry. In L. Ouwehand, editor, 20 Years of Progress in Radar Altimetry, volume 710 of ESA Special Publication, page 13, Sept. 2013. H. Hersbach, B. Bell, P. Berrisford, S. Hirahara, A. Hor ́anyi, J. Mu ̃noz-Sabater, J. Nicolas, C. Peubey, R. Radu, D. Schepers, et al. The ERA5 global reanalysis. Quarterly Journal of the Royal Meteorological Society, 146(730):1999–2049, 2020. doi: 10.1002/qj.3803. J. J. Leendertse. Aspects of a Computational Model for Long-period Water-wave Propagation. Rand Corporation for the United States Air Force Project Rand, 1967. LEGOS/CNRS/CLS. Dynamic atmospheric correction, 1992. URL https://www.aviso.altimetry.fr/en/data/products/auxiliary-products/dynamic-atmospheric-correction.html. G. S. Stelling. On the construction of computational methods for shallow water flow problems. PhD thesis, Delft University of Technology, Delft, 1984. Rijkswaterstaat Communications 35. </p

The impact of upwelling on the intensification of anticyclonic ocean eddies in the Caribbean Sea

Abstract. The mesoscale variability in the Caribbean Sea is dominated by anticyclonic eddies that are formed in the eastern part of the basin. These anticyclones intensify on their path westward while they pass the coastal upwelling region along the Venezuelan and Colombian coast. In this study, we used a regional model to show that this westward intensification of Caribbean anticyclones is steered by the advection of cold upwelling filaments. Following the thermal wind balance, the increased horizontal density gradients result in an increase in the vertical shear of the anticyclones and in their westward intensification. To assess the impact of variations in upwelling on the anticyclones, several simulations were performed in which the northward Ekman transport (and thus the upwelling strength) is altered. As expected, stronger (weaker) upwelling is associated with stronger (weaker) offshore cooling and a stronger (weaker) westward intensification of the anticyclones. Moreover, the simulations with weaker upwelling show farther advection of the Amazon and Orinoco River plumes into the basin. As a result, in these simulations the horizontal density gradients were predominantly set by horizontal salinity gradients. The importance of the horizontal density gradients driven by temperature, which are associated with the upwelling, increased with increasing upwelling strength. The results of this study highlight that both upwelling and the advection of the river plumes affect the life cycle of mesoscale eddies in the Caribbean Sea.info:eu-repo/semantics/publishe