Regional Sea Level Rise Research Articles

Projections of global-scale extreme sea levels and resulting episodic coastal flooding over the 21st Century

Global models of tide, storm surge, and wave setup are used to obtain projections of episodic coastal flooding over the coming century. The models are extensively validated against tide gauge data and the impact of uncertainties and assumptions on projections estimated in detail. Global “hotspots” where there is projected to be a significant change in episodic flooding by the end of the century are identified and found to be mostly concentrated in north western Europe and Asia. Results show that for the case of, no coastal protection or adaptation, and a mean RCP8.5 scenario, there will be an increase of 48% of the world’s land area, 52% of the global population and 46% of global assets at risk of flooding by 2100. A total of 68% of the global coastal area flooded will be caused by tide and storm events with 32% due to projected regional sea level rise.

Projections of Proper Beach Nourishment Volume as an Adaptation to Beach Recession based SLR along the Nile Delta Coastline of Egypt

Sharaan, M. and Udo, K., 2020. Projections of proper beach nourishment volume as an adaptation to beach recession based SLR along the Nile Delta coastline of Egypt. In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 637-642. Coconut Creek (Florida), ISSN 0749-0208.Beach loss and shoreline recession-based sea-level rise (SLR) is considered one of the most critical coastal issues worldwide. The Nile Delta coastline of Egypt is categorized as a low-lying and sandy coastal area that is prone to impacts of SLR. Beach nourishment is considered one of the most common adaptation strategies for erosion mitigation. Sandy beaches have a significant role in tourism, recreational purposes, and disaster prevention. The projection of proper beach nourishment volume (fill density) as an adaptation to beach loss-based SLR and land subsidence using the Bruun rule were investigated along the Nile Delta coastline of Egypt. The ensemble-mean regional SLR data included Representative Concentration Pathway (RCP) scenarios. Three main steps were applied to estimate the required proper beach nourishment volume. First, the future beach width due to SLR was estimated, and vulnerable areas to shoreline retreat were identified. Second, the targeted beach width to be protected in terms of coastal conservation, tourism purposes, and maintenance of the present beach was proposed based on Egyptian polices. Third, proper sand beach nourishment volume was estimated for four RCP scenarios, when local land subsidence is considered. The results show that the proper volume of beach nourishment required to maintain the beach width along the whole Nile Delta coastline varies from 24.8×106 to 145.5×106 m3 in 2100, with respect to RCP2.6 and RCP8.5, respectively.

Response of Storm-Related Extreme Sea Level along the U.S. Atlantic Coast to Combined Weather and Climate Forcing

AbstractStorm surge and coastal flooding caused by tropical cyclones (hurricanes) and extratropical cyclones (nor’easters) pose a threat to communities along the Atlantic coast of the United States. Climate change and sea level rise are altering the statistics of these extreme events in a rather complex fashion. Here we use a fully coupled global weather/climate modeling system (GFDL CM4) to study characteristics of extreme daily sea level (ESL) along the U.S. Atlantic coast and their response to global warming. We find that under natural weather processes, the Gulf of Mexico coast is most vulnerable to storm surge and related ESL. New Orleans is a striking hotspot with the highest surge efficiency in response to storm winds. Under a 1% per year atmospheric CO2 increase on centennial time scales, the anthropogenic signal in ESL is robust along the U.S. East Coast. It can emerge from the background variability as soon as in 20 years, or even before global sea level rise is taken into account. The regional dynamic sea level rise induced by the weakening of the Atlantic meridional overturning circulation facilitates this early emergence, especially during wintertime coastal flooding associated with nor’easters. Along the Gulf Coast, ESL is sensitive to the modification of hurricane characteristics under the CO2 forcing.

Low-frequency sea level variability and impact of recent sea ice decline on the sea level trend in the Arctic Ocean from a high-resolution simulation

The Arctic Ocean is undergoing significant changes, with rapid sea ice decline, unprecedented freshwater accumulation, and pronounced regional sea level rise. In this paper, we analyzed the sea level variation in the Arctic Ocean based on a global simulation with 4.5-km resolution in the Arctic Ocean using the multi-resolution Finite Element Sea Ice-Ocean Model (FESOM). The simulation reasonably reproduces both the main spatial features of the sea surface height (SSH) and its temporal evolution in the Arctic Ocean in comparison with tide gauge and satellite data. Using the model results, we investigated the low-frequency variability of the Arctic SSH. Both the first two dominant modes of the annual-mean SSH evolution in the Arctic Ocean present decadal variability and can be mainly attributed to the variability of the halosteric height, thus the freshwater content. The first mode can be explained by the Arctic Oscillation (AO). The AO-related atmospheric circulation drives the accumulation and release of freshwater in the Arctic deep basin and the consequent ocean mass change over the continental shelf, leading to the antiphase changes in SSH between the shelf seas and the deep basin. The second mode shows an antiphase oscillation between the two Arctic deep basins, the Amerasian and Eurasian Basins, which is driven by the Arctic dipole anomaly (DA). The DA-related wind anomaly causes a spatial redistribution of freshwater between the two basins, leading to the antiphase SSH changes. By using a dedicated sensitivity simulation in which the recent sea ice decline is eliminated, we find that the sea ice decline contributed considerably to the observed sea level rise in the Amerasian Basin in the recent decades. Although the sea ice decline did not change the mean SSH averaged over the Arctic Ocean, it significantly changed the spatial pattern of the SSH trend. Our finding indicates that both the wind regime and ongoing sea ice decline should be considered to better understand and predict the changes in regional sea level in the Arctic Ocean.

Regional Trends of Sea Level Rise along the Coast of Bangladesh

Bangladesh is becoming increasingly vulnerable to the growing threat of climate change induced sea level rise. Considering the potential severe impacts that sea level rise will have on the coastal population and the country’s economy, it has become very important to know about the regional trends of changing sea levels along the coastlands of Bangladesh. The present study attempted to portray a representative scenario of sea level rise in the coastal regions of Bangladesh. Historic tide gauge records, ranging from 20 to 45 years, were used to determine reliable trends at multiple locations along the coast. Linear regression method was applied to derive the changing trend of annual high, mean and low tidal water levels. The location-specific trends of sea level rise determined in this study can be helpful to planners and policy makers to combat the emerging threat of SLR in a more efficient manner.

Carbon and nutrient accumulation in mangrove sediments affected by multiple environmental changes

In order to assess the impact of anthropogenic activities on carbon and nutrient accumulation, total organic carbon (TOC), nitrogen (TN), and phosphorus (TP) accumulation rates were examined in a 210Pb-dated mangrove sediment core from Sepetiba Bay, Brazil, a coastal region impacted by multiple environmental changes during the previous century. A 50-cm length sediment core was collected from a mangrove forest in Sepetiba Bay. Sediment subsamples were analyzed to measure TOC, TN, δ13C, and δ15N using an elemental analyzer attached to an isotope ratio mass spectrometer Thermo Finnigan Model Delta Plus XP, whereas colorimetric analysis were used to measure TP. For 210Pbex analyses, gamma-ray measurements were performed in a semiplanar intrinsic germanium high purity coaxial detector, coupled to a multichannel analyzer, whereas the sediment accumulation rate (SAR) was calculated according to the constant initial concentration (CIC) method. Also, carbon and nutrient fluxes were calculated using SAR and TOC, TN, and TP contents, whereas statistical differences were evaluated by ANOVA + Tukey HSD analysis with previous data normalization. The calculated sedimentation rate (~ 8.1 mm year−1) since the early 1900s was up to threefold higher than the global mean determined for mangrove forests (~ 2.8 mm year−1) and the regional sea level rise (~ 3.2 mm year−1). Significantly higher TOC, TN, and TP fluxes, up to nearly 1000, 90, and 15 g m−2 year−1, respectively, were observed after the water diversion from a nearby drainage basin in the 1950s and an increase in sewage effluent input, which increased in the early 1990s. After this period, lighter δ13C values (~ − 25‰) indicate an increased importance of the terrestrial organic matter source, while lower TOC:TN ratios (~ 11) and heavier δ15N values (~ + 9‰) suggest an increased influence of anthropogenic fertilization on inorganic nitrogen accumulation. The significantly higher accumulation rates during the last decades evidenced the role of mangrove sediments as sinks for anthropogenically enhanced inputs of carbon and nutrients. Also, studies on carbon and nutrient accumulation evidenced the need for further research in eutrophic coastal areas.

Response of a salt marsh plant to sediment deposition disturbance

Salt marshes (a type of coastal wetland with herbaceous plants) are one of the most productive ecosystems. The organic matter accumulated by plants, together with deposition of inorganic mineral sediments, contributes to vertical marsh growth and determines the marsh ability to cope with regional sea level rise. Deposition of mineral sediment, in turn, alters the growth of plant roots and shoots, and further marsh morphology and blue carbon storage. Based on mesocosm experiments simulating the sedimentation intensity, this paper examined the responses of Spartina alterniflora (a plant widely distributed in global salt marshes) to sediment deposition events (0–24 cm thicknesses). The plant height increased by 1.51 cm on average with 1 cm sediment deposition. New roots grew into the deposited sediment layers, resulting in a significant increase in the below-ground biomass. The below-ground biomass doubled with the treatment of 24 cm deposition thickness in comparison with that without deposition. The depth-dependent distribution of below-ground biomass changed from a monotonous (decreasing with soil depth) to a non-monotonic (increasing first and then decreasing) trend. This illustrates the growth of marsh plants in response to sediment deposition disturbance (similar to artificial or storm-induced sediment deposition) and have important implications for further investigations on marsh resiliency, blue carbon storage and marsh morphology.

Poleward Shift of the Major Ocean Gyres Detected in a Warming Climate

AbstractRecent evidence shows that wind‐driven ocean currents, like the western boundary currents, are strongly affected by global warming. However, due to insufficient observations both on temporal and spatial scales, the impact of climate change on large‐scale ocean gyres is still not clear. Here, based on satellite observations of sea surface height and sea surface temperature, we find a consistent poleward shift of the major ocean gyres. Due to strong natural variability, most of the observed ocean gyre shifts are not statistically significant, implying that natural variations may contribute to the observed trends. However, climate model simulations forced with increasing greenhouse gases suggest that the observed shift is most likely to be a response of global warming. The displacement of ocean gyres, which is coupled with the poleward shift of extratropical atmospheric circulation, has broad impacts on ocean heat transport, regional sea level rise, and coastal ocean circulation.

Investigating the Acceleration of Regional Sea Level Rise During the Satellite Altimeter Era

AbstractThe 25‐year record of satellite altimeter‐measured sea level has led to improvements in the understanding of sea level change on both regional and global scales. However, the extent to which the pattern of regional sea level rise measured by altimeters is representative of the forced sea level response remains an open question. Internal variability both contributes to regional sea level changes on short time scales and masks the pattern of forced trend and acceleration associated with anthropogenic global warming. Recent studies have demonstrated that the forced trend pattern of regional rise has begun to emerge, although there has been no assessment of a possible associated acceleration. Here, the regional acceleration pattern is estimated from the altimeter sea level record and assessed with regard to the influence of internal variability. While the dominant features in the acceleration pattern can be attributed to internal variability, there is an indication that the forced acceleration pattern may emerge as the record continues to lengthen.

Teaching modules for estimating climate change impacts in economics courses using computational guided inquiry

The authors of this article introduce two teaching modules that aim to increase climate literacy and active learning in undergraduate economics courses through the incorporation of real-world data and modeling. These modules are based on the concept of computational guided inquiry (CGI), which combines a guided inquiry approach within a computational framework, such as Excel. In one module, students estimate and graph expected marginal damages due to regional sea level rise for various polar ice melt scenarios. In the second module, students partially replicate a journal article estimating the total economic value of ecosystem services in the Arctic. These modules have been used in urban, environmental, and climate change economics courses, and are ready to be implemented with minimal upfront cost to instructors.

Modeling of climate change impacts on Lake Burullus, coastal lagoon (Egypt)

Coastal lagoons are particularly vulnerable to climate change, in particular, Sea Level Rise (SLR) due to their shallowness. Lake Burullus provides a variety of socio-economic services as the second largest coastal lagoon in Egypt. Recently, it has experienced significant ecological deterioration. Thus, its ecosystem is fragile in the face of anthropogenic induced changes. The main objective of the current study is to investigate the climate change impacts on characteristics of Lake Burullus. A depth averaged hydro-ecological modeling system, MIKE21, was applied to develop an eco - hydrodynamic model for the lake. The developed model was calibrated and verified for two successive years: July 2011–June 2012 and July 2012–June 2013. The model simulations exhibited good agreement with the measurements during the calibration and verification processes. Six different Regional Climate Models (RCMs) were compared, using six different statistical metrics, to determine the most accurate one for the study area. The required meteorological input, including surface air temperature, precipitation, and evaporation were derived from the selected RCM. The meteorological input was extracted for two different years in the 21 st century considering one Representative Concentration Pathways (RCPs) scenario, based on the Intergovernmental Panel on Climate Change (IPCC) 5th Report. Regional SLR projections for the Mediterranean Sea for the selected RCP scenario and the two studied years were obtained. These future climate change estimates were used to modify the validated model of the lake. A sensitivity analysis was applied to assess effect of future climatic conditions and SLR, separately. The results revealed that the lake water depths will increase and it will be warmer and more saline. Significant spatial variability of the studied parameters under climate change forcing is expected. Consequently, climate change is going to restrict the lake's ability to preserve the present-day species. An urgent management plan involving adaptation works, should be implemented to reduce such potential species losses in Egyptian lagoons.

Population Genetic Structure of A Marine Pelagic Egg Producer and Popular Marine Aquarium Species, the Mandarinfish Synchiropus splendidus.

The mandarinfish Synchiropus splendidus is extensively collected in Southeast Asia (mainly in the Philippines) and highly favoured for the marine aquarium trade. Males are more popular than females for their large first dorsal fins and the fishery is not managed. To examine possible population replenishment dynamics arising as a result of selective fishing, the effects of sex-selective fishing on sex ratios and population connectivity were considered. This study determined the sex ratios and analyzed the population genetic structure from mandarinfish collected at six locations: one from Palau, where the species is not exploited, and five from Bohol in the Philippines, where the species has long been heavily fished. The findings reported very low male to female ratios (0.12 to 0.30) from four of the five locations in Bohol, with relatively more males to females in the specimens collected from Palau (2.3). The analyses from allozymes (43 alleles from 10 loci) and microsatellites (118 alleles from 5 loci) revealed that genetic connectivity was high among the five locations in the Philippines as well as with the specimens collected from the more-distant Palau. The genetic homogeneity observed across the geographical range considered is inconsistent with the hypothesized limited dispersal ability of the species and could be explained by recent species range expansion associated with sea level rise in the region. The results suggest that the present genetic structure, at least in the geographic region considered, may not be determined by current patterns of gene flow, but may, instead, be driven by recent sea-level changes associated with periods of glaciation. Caution is suggested to ensure that heavily localized fishing does not produce excessively biased adult sex ratios.

Likely and High-End Impacts of Regional Sea-Level Rise on the Shoreline Change of European Sandy Coasts Under a High Greenhouse Gas Emissions Scenario

Sea-level rise (SLR) is a major concern for coastal hazards such as flooding and erosion in the decades to come. Lately, the value of high-end sea-level scenarios (HESs) to inform stakeholders with low-uncertainty tolerance has been increasingly recognized. Here, we provide high-end projections of SLR-induced sandy shoreline retreats for Europe by the end of the 21st century based on the conservative Bruun rule. Our HESs rely on the upper bound of the RCP8.5 scenario “likely-range” and on high-end estimates of the different components of sea-level projections provided in recent literature. For both HESs, SLR is projected to be higher than 1 m by 2100 for most European coasts. For the strongest HES, the maximum coastal sea-level change of 1.9 m is projected in the North Sea and Mediterranean areas. This translates into a median pan-European coastline retreat of 140 m for the moderate HES and into more than 200 m for the strongest HES. The magnitude and regional distribution of SLR-induced shoreline change projections, however, utterly depend on the local nearshore slope characteristics and the regional distribution of sea-level changes. For some countries, especially in Northern Europe, the impacts of high-end sea-level scenarios are disproportionally high compared to those of likely scenarios.

Projections of future beach loss along the mediterranean coastline of Egypt due to sea-level rise

Beach loss and shoreline retreat caused by sea level rise (SLR) is considered one of the most worldwide significant issues. The Mediterranean coastline of Egypt (approximately 1066 km) is likely to face beach erosion, particularly in the low-lying and sandy coastal areas in the future as a direct response to SLR. Consequently, the projection of future shoreline recession and corresponding beach loss due to SLR using the Bruun rule were investigated to assess the proper impacts of SLR on the shoreline recession and beach loss. In addition, the uncertainties ratios associated with SLR scenarios and sediment sizes were assessed. Furthermore, this study investigated the influence of local land subsidence in combination with SLR scenarios on the shoreline recession and associated beach loss along the Nile Delta coastline. The ensemble-mean regional SLR data included representative concentration pathway (RCP) scenarios and 21 models of the Coupled Model Intercomparison Project Phase 5 (CMIP5). The projected shoreline retreats and associated average beach loss in the future 2081–2100 were ranged from 12.6 m and 11.3 km2 to 41.9 m and 19.2 km2 for the ensemble-mean SLR RCP2.6 and RCP8.5, respectively. The uncertainty caused by the sediment size of 0.15 to 0.35 mm ranged from 17% to 30% for RCP2.6 and RCP8.5, respectively. The projected annual shoreline retreats ranged from 0.36 to 0.65 m/yr for the ensemble-mean SLR in combination with local land subsidence for RCP2.6 and 0.48 to 0.85 m/yr for RCP8.5, respectively. Highly vulnerable areas to shoreline recession for SLR and local land subsidence were detected from EL-Manzala lake to Port Said coastlines, Abo Qir bay, from Rosetta to Damietta promontories, and Alexandria coastline. Thus, shoreline retreat and associated beach loss due to SLR is an urgent issue that should be addressed through the integrated coastal zone management strategies of Egypt.

Carbonate ramp drowning caused by flexural subsidence: The South Pyrenean middle Eocene foreland basin

A detailed sedimentological and magnetostratigraphic analysis of three selected sections of the Eocene carbonate platforms of the South Pyrenean Jaca-Pamplona foreland basin has been carried out in the Aragonese External Sierras (Huesca, Spain). The stratigraphic record spans from the middle-late Lutetian (Chron 20r, SBZ15) to the Bartonian (Chron 18r, SBZ17). The Lutetian-Bartonian transition was characterized by a major paleogeographic change, from a turbiditic foredeep with associated peripheral carbonate ramps to deltaic sedimentation. In most of the outcrops of the External Sierras, the peripheral carbonate platforms (Guara Formation) are overlained by prodelta and outer ramp marls (Arguis Formation). The drowning unconformity between these two formations in the outcrops located in the westernmost tip of the External Sierras is documented herein for the first time. In this area, the Guara Formation is overlain by glauconitic limestones deposited in a carbonate ramp setting. Between these units a characteristic unconformity is observed, with hard-ground formation and local evidence of subaerial exposure in the shallowest domains of the study area. The abundant glauconite found on top of this unconformity records a starvation period in the basin, followed by the development of a new carbonate ramp system during Bartonian times (Santo Domingo Member of the Arguis Formation). Magnetostratigraphic and sedimentological data show that tectonic tilting occurred in latest Lutetian times, prior to the drowning process. This suggests the influence of the flexural subsidence in the cratonic margin of the foreland as a result of the advance of a basement thrust in the hinterland. Nevertheless, the correlation of the uppermost Lutetian drowning unconformity with a basinwide regional sea level rise, which may have further been global, suggests an interplay between tectonic and eustatic processes in the drowning of the late Lutetian South Pyrenean carbonate ramps. In this work we point out a narrowing of the carbonate ramp, together with a relative sea level rise, as the processes responsible for the drowning of the Upper Guara Mb carbonate ramp. These processes could be responsible for the development of drowning unconformities in cratonic margins of other foreland basins. As carbonate ramps have a high sediment production potential, the narrowing of the carbonate factory could provide the conditions for the drowning of the carbonate ramp system in a subsequent sea level rise.

Impacts of the mid-latitude westerlies anomaly on the decadal sea level variability east of China

The present analysis has revealed that both the altimetry and tide gauge records show a prominent sea level rise from 1993 to 2016 in the coastal seas east of China, including Bohai, Yellow Sea, and East China Sea (BYECS). The regional mean sea level rise rate for the BYECS continental shelf area is ~ 3.2 mm/year, which is close to the global mean (2.9 mm/year). Besides the rising trend, the BYECS sea level anomaly (SLA) also shows obvious interannual and decadal oscillation. It is found that the mid-latitude westerlies, rather than the steric height variability, are responsible for these oscillations. By analyzing the 67-year (1950–2016) hindcast outputs from an eddy-resolving ocean general circulation model, a 14.2 years decadal period is found to dominate the BYECS SLA variability, and the decadal oscillation is positively correlated with the North Pacific Gyre Oscillation (NPGO). The composite analysis and causality analysis demonstrate that during the positive phase of the NPGO, the mid-latitude westerlies decrease and a positive wind stress curl anomaly at the same latitude of the East China Sea’s Kuroshio occurs to the south of the westerlies. Consequently, the Kuroshio Current volume transport and sea surface height difference between the two sides of the Kuroshio decrease, that is, the sea level in the BYECS rises.

Introducing a vertical land motion model for improving estimates of sea level rates derived from tide gauge records affected by earthquakes

We reassess the absolute and relative sea level changes at 38 tide gauge stations in the earthquake-affected Western North Pacific for the 1993–2015 period, focusing on the vertical land motion (VLM) which is crucial for narrowing the gap between these estimates. In this area, simply discarding all earthquake-affected sites, one overestimates the average regional sea level rise by more than 0.5 mm/year. Disregarding VLM would lead to misestimating local sea level trends between 0.2 and 7.6 mm/year. If accounted for, but modeled as linear during the entire time span, VLM leads to regional absolute sea level rise errors of up to 0.4 mm/year. Therefore, we introduce a new methodology that better represents the Global Positioning System (GPS)-derived nonlinear VLM by accounting for co-seismic offsets, changes in the vertical velocities and post-seismic transient. Also, for the first time, a combination of white and power-law noises is added to this nonlinear model to derive proper uncertainties of VLM. We find a maximum difference of 15.3 mm/year between pre- and post-seismic vertical velocities. The GPS-sensed vertical co-seismic displacement approaches 36 mm. Assuming the changes in vertical velocities and displacement due to the tectonic movements is not accounted for, and then, estimating absolute sea level rise from tide gauges can result in an error of 10 mm/year. Introducing a new nonlinear VLM model improves absolute tide gauge sea level estimates by 20% on average. Finally, for the reconstructed Western North Pacific sea level, altimetry agrees best with tide gauge data corrected employing the new nonlinear VLM model.

North Atlantic Ocean Circulation and Decadal Sea Level Change During the Altimetry Era

Regional sea-level rise is characterized by decadal acceleration and deceleration periods that typically stem from oceanic climate variability. Here, we investigate decadal sea-level trends during the altimetry era and pin down the associated ocean circulation changes. We find that decadal subpolar gyre cooling (warming), strengthening (weakening), widening (shrinking) since the mid-2000s (early 1990s) resulted in negative (positive) sea level trends of −7.1 mm/yr ± 1.3 mm/yr (3.9 mm/yr ± 1.5 mm/yr). These large-scale changes further coincide with steric sea-level trends, and are driven by decadal-scale ocean circulation variability. Sea level on the European shelf, however, is found to correlate well with along-slope winds (R = 0.78), suggesting it plays a central role in driving the associated low-frequency dynamic sea level variability. Furthermore, when the North Atlantic is in a cooling (warming) period, the winds along the eastern boundary are predominantly from the North (South), which jointly drive a slowdown (rapid increase) in shelf and coastal sea level rise. Understanding the mechanisms that produce these connections may be critical for interpreting future regional sea-level trends.

Palaeoenvironmental evolution from the early Holocene to the present of the Almenara marsh (western Mediterranean)

The main aim of this study is to characterize the different stages in the palaeoenvironmental evolution of the Almenara marsh, Spain, from the early Holocene to the present day. This marsh is one of the most important in Castellón province. Five cores extracted from the marsh underwent sedimentological analysis, micropalaeontological study (foraminifera, ostracods and gastropods) and 14C dating. The results show that before the maximum transgression of the Mediterranean during the Marine Isotope Stage 1 (5500 cal yr. BP dating in the Almenara marsh), the area was occupied by a brackish marsh (prior to the 8.2 ka event). During the middle Holocene, the regional sea level rise and later stability caused an oligohaline/freshwater marsh with fluctuating water levels to form. This marsh occupied the entire area of today’s Almenara marsh at least between 7570 and 2780 cal yr BP. The results may indicate a phase of greater contribution of groundwater inputs (and rainfall/riverine discharge) during the middle Holocene as a response to a climatic phase characterized by higher humidity. Today, the marsh is filled with sediments from natural and anthropic processes related to the agricultural activity carried out throughout the area (except for the central part, which has been reclaimed as wetland). The water of the present-day marsh (like that prior to 8.2 ka event) is brackish, as is indicated by the benthic foraminiferal assemblage; this contrasts with the earlier oligohaline/freshwater marsh determined in the survey cores during the middle Holocene until the time of the Iberian culture.

Global sea-level contribution from Arctic land ice: 1971–2017

The Arctic Monitoring and Assessment Program (AMAP 2017) report identifies the Arctic as the largest regional source of land ice to global sea-level rise in the 2003–2014 period. Yet, this contextualization ignores the longer perspective from in situ records of glacier mass balance. Here, using 17 (>55 °N latitude) glacier and ice cap mass balance series in the 1971–2017 period, we develop a semi-empirical estimate of annual sea-level contribution from seven Arctic regions by scaling the in situ records to GRACE averages. We contend that our estimate represents the most accurate Arctic land ice mass balance assessment so far available before the 1992 start of satellite altimetry. We estimate the 1971–2017 eustatic sea-level contribution from land ice north of ∼55 °N to be 23.0 ± 12.3 mm sea-level equivalent (SLE). In all regions, the cumulative sea-level rise curves exhibit an acceleration, starting especially after 1988. Greenland is the source of 46% of the Arctic sea-level rise contribution (10.6 ± 7.3 mm), followed by Alaska (5.7 ± 2.2 mm), Arctic Canada (3.2 ± 0.7 mm) and the Russian High Arctic (1.5 ± 0.4 mm). Our annual results exhibit co-variability over a 43 year overlap (1971–2013) with the alternative dataset of Marzeion et al (2015 Cryosphere 9 2399–404) (M15). However, we find a 1.36× lower sea-level contribution, in agreement with satellite gravimetry. The IPCC Fifth Assessment report identified constraining the pre-satellite era sea-level budget as a topic of low scientific understanding that we address and specify sea-level contributions coinciding with IPCC Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) ‘present day’ (2005–2015) and ‘recent past’ (1986–2005) reference periods. We assess an Arctic land ice loss of 8.3 mm SLE during the recent past and 12.4 mm SLE during the present day. The seven regional sea-level rise contribution time series of this study are available from AMAP.no.