Relative Mean Sea Level Research Articles

Mean sea level, tidal components and surges in Guanabara Bay (Rio de Janeiro) from 1990 to 2021

AbstractGuanabara Bay, located in the Metropolitan Region of Rio de Janeiro, one of the largest urban coastal areas in the Southern Hemisphere, is subject to intense maritime traffic due to the presence of several ports. These facilities are affected by sea level fluctuations, influenced by atmospheric and astronomical forces, which motivates synoptic and climatological analysis, including meteorological and astronomical tidal phenomena. This study aimed to assess the evolution of tidal components and the relative mean sea level (MSL) between 1990 and 2021, as well as the atmospheric influence on extreme meteorological tide events, in which the MSL exceeded ±2 and ±3 (±29.98 and ±44.97 cm) standard deviations. The results have shown that, albeit small, the main tidal components (, , , , , , and ) indicated positive trends in the increase of amplitude and phase, despite the small quantities. For the relative MSL, an increase of 0.30 cm·year−1 was observed in agreement with estimates from global series from satellite altimeters and climate model predictions. Pressure and wind field analyses led to the identification of seasonal variability and the pattern of evolution of atmospheric systems associated with extreme events. In the case of positive surges, very intense winds from the SW, extending along the S/SE Brazilian coast, are caused by the presence of a high‐pressure centre over the continent and low‐pressure centres over the ocean, leading to water piling up. In turn, negative surges are caused by the presence of an anticyclone over the ocean, generating NE winds parallel to the coast of Rio de Janeiro, inducing Ekman transport and lowering the sea level. Therefore, the extreme sea level events in the Guanabara Bay are not triggered by local forces, but rather depend on the temporal persistence and direction of winds along the S/SE Brazilian coast.

Sea level and temperature extremes in a regulated Lagoon of Venice

Increasing sea levels and water temperatures have been detected at several coastal locations worldwide with severe consequences on the communities and ecosystems. Coastal lagoons are particularly vulnerable to such changes due to their low land elevation and limited connections with the open sea. Here the recent and future climatic changes in the Lagoon of Venice (Italy) are investigated using in-situ observations and high-resolution hydrodynamic modeling. Trend analysis was applied to observed time series of meteorological and oceanographic climate essential variables to identify significant long-term changes in mean and extreme values. The mean relative sea level rose at a rate of 4.9 mm per year in Venice due to the combined action of eustacy and subsidence while air and sea temperatures increased on average by 1.8 and 1.1°C in 30 years, respectively. These rates, as well as climate projections, were used following a pseudo-global-warming approach to investigate the near future (up to 2050) evolution of the lagoon's dynamics focusing on sea level and temperature extremes. The lagoon will amplify the temperature changes expected for the Adriatic Sea, especially in the shallow tidal flats where the intensity of the marine heat waves will be more than four times larger than that in the open sea. Moreover, the model allowed us to perform “what-if” scenarios to explore to which extent the flood protection MoSE barriers will modify the lagoon's dynamics. According to the simulations, the number of floods and therefore of the MoSE closure strongly increases with sea level rise. In the most severe scenario, MoSE will have to close for more than 20% of the time in October, November, and December resulting in the reduction of water exchange with the open sea and exacerbation of marine cold spells. Some considerations on the implications of the expected changes on the lagoon's ecology are proposed.

Causes of accelerated High-Tide Flooding in the U.S. since 1950

The U.S. coastlines have experienced rapid increases in occurrences of High Tide Flooding (HTF) during recent decades. While it is generally accepted that relative mean sea level (RMSL) rise is the dominant cause for this, an attribution to individual components is still lacking. Here, we use local sea-level budgets to attribute past changes in HTF days to RMSL and its individual contributions. We find that while RMSL rise generally explains > 84% of long-term increases in HTF days locally, spatial patterns in HTF changes also depend on differences in flooding thresholds and water level characteristics. Vertical land motion dominates long-term increases in HTF, particularly in the northeast, while sterodynamic sea level (SDSL) is most important elsewhere and on shorter temporal scales. We also show that the recent SDSL acceleration in the Gulf of Mexico has led to an increase of 220% in the frequency of HTF events over the last decade.

ANALYSIS OF VERTICAL LAND MOTIONS ALONG THE CHILEAN COAST CONSIDERING SEA LEVEL VARIABILITY, EARTHQUAKE AND CRUSTAL DEFORMATION OF SUBDUCTION ZONES

Chile is one of the most seismic countries world wide with approximately 86.000 km of coastline and a permanent need for development and management. Because of the Nazca plate subducting the South American plate, coastal evolution is modeled by oceanographic variables and plate tectonics Coastal towns are under permanent tsunami and storm risks unregulated real estate development and climate driven sea level rise (SLR) IPCC AR6 SSP5 8.5 scenario summarized future trend s in absolute mean sea level (AMSL) of ~ 0.1 m in the near term (2021 2040), 0.2 m in the medium term (2041 2060) and 0.6 m in the long term (2081 2100 ) along the coast . However, relative sea level is affected by large coseismic uplift and/or subsidence which may be comparable to or larger than SLR ( Montecino et al., 2017) The combination of SLR, earthquake and crustal deformation is important for long term development. Using satellite and tidal gauge data a comparison between the AMSL and relative mean sea level RMSL) was conducted for different locations along the Chilean coast between 1993 and 2020.

The effect of tidal range and mean sea-level changes on coastal flood hazards at Lakes Entrance, south-east Australia

Despite being well-documented in other countries, the roles that anthropogenically induced changes and natural variability in tidal processes play in modulating coastal flood frequencies have not been investigated in Australia. Here we conduct a brief assessment of changes in tidal variability around Australia. We then apply a simple attribution framework to quantify the separate and joint effects of tidal range changes and increasing relative mean sea level on nuisance flood frequency at the location with the largest relative changes in tidal range, Lakes Entrance, Victoria. To understand how these changes in variability affect flood hazards, we consider a nuisance flood threshold based on recent coastal flood impact surveys. Results show that increases in the heights of high tides over recent years have exerted a large influence on coastal flood frequencies. These recent changes are potentially linked to changes in channel dredging regimes. We show that 93% of nuisance flood days since 2009 would not have occurred without these tidal range changes or the coincident increases in the mean sea level. We demonstrate the importance of considering tidal processes in estuarine coastal flood hazard assessments for future planning, even if these processes do not represent a substantial flood threat today. We discuss the implications of this study for future work on estuarine flood hazards and the benefits of considering impact-based thresholds in the assessment of such hazards.

Epoch-Based Height Reference System for Sea Level Rise Impact Assessment on the Coast of Peninsular Malaysia

The Peninsular Malaysia Geodetic Vertical Datum 2000 (PMGVD2000) inherited several deficiencies due to offsets between local datums used, levelling error propagations, land subsidence, sea level rise, and sea level slopes along the southern half of the Malacca Strait on the west coast and the South China Sea in the east coast of the Peninsular relative to the Port Klang (PTK) datum point. To cater for a more reliable elevation-based assessment of both sea level rise and coastal flooding exposure, a new epoch-based height reference system PMGVD2022 has been developed. We have undertaken the processing of more than 30 years of sea level data from twelve tide gauge (TG) stations along the Peninsular Malaysia coast for the determination of the relative mean sea level (RMSL) at epoch 2022.0 with their respective trends and incorporates the quantification of the local vertical land motion (VLM) impact. PMGVD2022 is based on a new gravimetric geoid (PMGeoid2022) fitted to the RMSL at PTK. The orthometric height is realised through the GNSS levelling concept H = hGNSS–Nfit_PTK–NRMDT, where NRMDT is a constant offset due to the relative mean dynamic ocean topography (RMDT) between the fitted geoid at PTK and the local MSL datums along the Peninsular Malaysia coast. PMGVD2022 will become a single height reference system with absolute accuracies of better than ±3 cm and ±10 cm across most of the land/coastal area and the continental shelf of Peninsular Malaysia, respectively.

A 3-kyr plateau of middle Holocene higher sea levels on the central Kanto Plain, Japan

Middle Holocene higher sea levels during 7–4 ka in Asia, Australia, and South America varied in duration and stability. Abundant archaeological excavations have been carried out in the Tokyo urban area, which is situated on the alluvial and coastal lowlands of the central Kanto Plain. In this study, 74 sea-level index points and 241 limiting data points were compiled from Japanese scientific papers and excavation reports for 109 locations on the central Kanto Plain. These data suggest that the relative mean sea level changed from −4 ± 1.5 m at 8 ka to 3 ± 1.5 m during 7–4 ka, to −1.5 ± 1 m at 3 ka, and then to 0 ± 1 m during 2–0 ka. During the 7–4-ka sea-level plateau on the central Kanto Plain, the sea level did not fluctuate. The height distribution at 52 locations on the central Kanto Plain shows that sea level remained stable for 3 kyr, with no local differences in the duration, in an area of 90 km × 90 km. The temporary sea-level drop at 3 ka corresponds to the “Yayoi regression”, which has been previously reported on the central Kanto Plain, although its driving mechanism is unknown. Crustal deformation can be neglected as less important than the spring tidal range, which was ca. 3 m at 7 ka on the central Kanto Plain. By using a dense dataset to confirm the occurrence of a middle Holocene higher sea-level plateau on the central Kanto Plain, this study strongly suggests that glacier melting occurred two steps, at 7 ka and 4 ka.

Rapid sea-level rise during the first phase of the Littorina transgression in the western Baltic Sea

Glacio-isostatic adjustment (GIA) corrected limiting non-marine and marine sea-level data from the western Baltic Sea indicate a rapid relative sea-level (RSL) rise of 18 m for the first phase of the Littorina transgression using a linear age-elevation model. This accelerated RSL rise occurred in the time period 8.57 to 8.0 ka before present (BP) with an RSL rise rate of 31.5 mm/year. RSL rose from 28 m to 10 m below the mean relative sea level (bmrsl) during the time period of less than 600 years. The first phase of Littorina transgression documents the last big meltwater pulse (MWP), which has been reported also from various other regions in the world as a consequence of the final decay of the Laurentide ice sheet and additional meltwater sources from Antarctica.

Recent atmospheric changes and future projections along the Saudi Arabian Red Sea Coast

Recent and future climate diagrams (surface air temperature, surface relative humidity, surface wind, and mean sea level pressure) for the Saudi Arabian Red Sea Coast are analysed based on hourly observations (2016–2020) and hourly ERA5 data (1979–2020) with daily GFDL mini-ensemble means (2006–2100). Moreover, GFDL mini-ensemble means are calculated based on the results of three GFDL simulations (GFDL-CM3, GFDL-ESM2M, and GFDL-ESM2G). Observation data are employed to describe the short-term current weather variability. However, ERA5 data are considered to study the long-term current weather variability after bias removal via a comparison to observations. Finally, a bias correction statistical model was developed by matching the cumulative distribution functions (CDFs) of corrected ERA5 and mini-ensemble mean data over 15 years (2006–2020). The obtained local statistic were used to statically downscale GFDL mini-ensemble means to study the future uncertainty in the atmospheric parameters studied. There occurred significant spatial variability across the study area, especially regarding the surface air temperature and relative humidity, based on monthly analysis of both observation and ERA5 data. Moreover, the results indicated that the ERA5 data suitably describe Tabuk, Jeddah and Jizan weather conditions with a marked spatial variability. The best performance of ERA5 surface air temperature and relative humidity (surface wind speed and sea level pressure) data was detected in Tabuk (Jeddah). These data for the Saudi Arabian Red Sea coast, 1979–2020, exhibit significant positive trends of the surface air temperature and surface wind speed and significant negative trends of the relative humidity and sea level pressure. The GFDL mini-ensemble mean projection result, up to 2100, contains a significant bias in the studied weather parameters. This is partly attributed to the coarse GFDL resolution (2° × 2°). After bias removal, the statistically downscaled simulations based on the GFDL mini-ensemble mean indicate that the climate in the study area will experience significant changes with a large range of uncertainty according to the considered scenario and regional variations.

Coastal erosion in sandy beaches along a tectonically active coast: The Chile study case

Coastal erosion in 45 sandy beaches covering nearly 2000 km along the tectonically active Chilean coast is assessed during the last four decades. The historical analysis is based on the assessment of decadal changes of the shoreline position extracted from topographic surveys, aerial photographs, satellite images and survey maps using the DSAS software. Results show that 80% of the sites presented erosion rates (>−0.2 m/y), 7% beaches accreted (>0.2 m/y) while 13% remained stable. Eroded beaches include headland bay beaches, embayed and pocket beaches. A discussion on the possible causes explaining these results is conducted. While changes in offshore wave climate are spatially smooth within the region, relative mean sea level changes are highly variable and modulated by tectonic activity; the reduction of the sediment supply explains erosion rates in few cases.

Extreme floods of Venice: characteristics, dynamics, past and future evolution (review article)

Abstract. Floods in the Venice city centre result from the superposition of several factors: astronomical tides; seiches; and atmospherically forced fluctuations, which include storm surges, meteotsunamis, and surges caused by atmospheric planetary waves. All these factors can contribute to positive water height anomalies individually and can increase the probability of extreme events when they act constructively. The largest extreme water heights are mostly caused by the storm surges produced by the sirocco winds, leading to a characteristic seasonal cycle, with the largest and most frequent events occurring from November to March. Storm surges can be produced by cyclones whose centres are located either north or south of the Alps. Historically, the most intense events have been produced by cyclogenesis in the western Mediterranean, to the west of the main cyclogenetic area of the Mediterranean region in the Gulf of Genoa. Only a small fraction of the inter-annual variability in extreme water heights is described by fluctuations in the dominant patterns of atmospheric circulation variability over the Euro-Atlantic sector. Therefore, decadal fluctuations in water height extremes remain largely unexplained. In particular, the effect of the 11-year solar cycle does not appear to be steadily present if more than 100 years of observations are considered. The historic increase in the frequency of floods since the mid-19th century is explained by relative mean sea level rise. Analogously, future regional relative mean sea level rise will be the most important driver of increasing duration and intensity of Venice floods through this century, overcompensating for the small projected decrease in marine storminess. The future increase in extreme water heights covers a wide range, largely reflecting the highly uncertain mass contributions to future mean sea level rise from the melting of Antarctica and Greenland ice sheets, especially towards the end of the century. For a high-emission scenario (RCP8.5), the magnitude of 1-in-100-year water height values at the northern Adriatic coast is projected to increase by 26–35 cm by 2050 and by 53–171 cm by 2100 with respect to the present value and is subject to continued increase thereafter. For a moderate-emission scenario (RCP4.5), these values are 12–17 cm by 2050 and 24–56 cm by 2100. Local subsidence (which is not included in these estimates) will further contribute to the future increase in extreme water heights. This analysis shows the need for adaptive long-term planning of coastal defences using flexible solutions that are appropriate across the large range of plausible future water height extremes.

Sea level dynamics and coastal erosion in the Baltic Sea region

Abstract. There are a large number of geophysical processes affecting sea level dynamics and coastal erosion in the Baltic Sea region. These processes operate on a large range of spatial and temporal scales and are observed in many other coastal regions worldwide. This, along with the outstanding number of long data records, makes the Baltic Sea a unique laboratory for advancing our knowledge on interactions between processes steering sea level and erosion in a climate change context. Processes contributing to sea level dynamics and coastal erosion in the Baltic Sea include the still ongoing viscoelastic response of the Earth to the last deglaciation, contributions from global and North Atlantic mean sea level changes, or contributions from wind waves affecting erosion and sediment transport along the subsiding southern Baltic Sea coast. Other examples are storm surges, seiches, or meteotsunamis which primarily contribute to sea level extremes. Such processes have undergone considerable variation and change in the past. For example, over approximately the past 50 years, the Baltic absolute (geocentric) mean sea level has risen at a rate slightly larger than the global average. In the northern parts of the Baltic Sea, due to vertical land movements, relative mean sea level has decreased. Sea level extremes are strongly linked to variability and changes in large-scale atmospheric circulation. The patterns and mechanisms contributing to erosion and accretion strongly depend on hydrodynamic conditions and their variability. For large parts of the sedimentary shores of the Baltic Sea, the wave climate and the angle at which the waves approach the nearshore region are the dominant factors, and coastline changes are highly sensitive to even small variations in these driving forces. Consequently, processes contributing to Baltic sea level dynamics and coastline change are expected to vary and to change in the future, leaving their imprint on future Baltic sea level and coastline change and variability. Because of the large number of contributing processes, their relevance for understanding global figures, and the outstanding data availability, global sea level research and research on coastline changes may greatly benefit from research undertaken in the Baltic Sea.

Intense windstorms in the northeastern United States

Abstract. Windstorms are a major natural hazard in many countries. The objective of this study is to identify and characterize intense windstorms during the last 4 decades in the US Northeast and determine both the sources of cyclones responsible for these events and the manner in which those cyclones differ from the cyclone climatology. The windstorm detection is based on the spatial extent of locally extreme wind speeds at 100 m height from the ERA5 reanalysis database. During the top 10 windstorms, wind speeds exceed their local 99.9th percentile over at least one-third of land-based ERA5 grid cells in this high-population-density region of the USA. Maximum sustained wind speeds at 100 m during these windstorms range from 26 to over 43 ms−1, with wind speed return periods exceeding 6.5 to 106 years (considering the top 5 % of grid cells during each storm). Property damage associated with these storms, with inflation adjusted to January 2020, ranges from USD 24 million to over USD 29 billion. Two of these windstorms are linked to decaying tropical cyclones, three are Alberta clippers, and the remaining storms are Colorado lows. Two of the 10 re-intensified off the east coast, leading to development of nor'easters. These windstorms followed frequently observed cyclone tracks but exhibit maximum intensities as measured using 700 hPa relative vorticity and mean sea level pressure that is 5–10 times the mean values for cyclones that followed similar tracks over this 40-year period. The time evolution of wind speeds and concurrent precipitation for those windstorms that occurred after the year 2000 exhibit good agreement with in situ ground-based and remote sensing observations, plus storm damage reports, indicating that the ERA5 reanalysis data have a high degree of fidelity for large, damaging windstorms such as these. A larger pool of the top 50 largest windstorms exhibit evidence of only weak serial clustering, which is in contrast to the relatively strong serial clustering of windstorms in Europe.

Neapolitan volcanic area Tide Gauge Network (Southern Italy): Ground Displacements and Sea-Level Oscillations

Abstract. In this study, we investigate the oscillations of relative sea level through the analysis of tide gauge records about 10-year long collected in the Gulfs of Pozzuoli and Napoli (Southern Italy). The main goal of this study is to provide a suitable resolution model of the sea tides including low frequency (seiches), tidal bands and non-linear tides. The spectral analyses of the tide gauge records lead us to identify a number of seiche periods some of them already known from the literature and some other unknown. Furthermore, we target a non-conventional purpose of the tidal analysis, namely extracting from the tide gauge records the volcano-tectonic signal (vertical ground displacement) in the resurgent Campi Flegrei caldera. We suggest a method to filter out the volcano-tectonic signal (bradyseism) from the tide gauge records by deconvolving it from two records, one collected in the active volcanic area (Pozzuoli) and the other one collected in a tectonically stable station (Napoli), located beyond the caldera rim. Finally, we retrieve the relative mean sea level change in the Gulf of Naples and compare it with the trend found in five tide gauges spread along the Italian coast.

Effects of sea level rise on storm surges in the south Yellow Sea: A case study of Typhoon Muifa (2011)

Changes in sea levels due to climate change are expected to alter storm surge intensities worldwide, disproportionately effecting coastal communities. In this study, we explored the impacts of future sea level rise (SLR) on storm surges within various numerical frameworks. The relative mean sea level rise (RMSLR) scenario for a period of 100-yr was applied using satellite altimetry of sea surface height and subsequently adjusted for the influence of glacial isostatic adjustment (GIA) using the ICE-6G/VM5a model. For comparison purpose, two additional RMSLR distributions under Representative Concentration Pathway (RCP) scenarios were also evaluated from climate system model (CSM) ensembles and GIA. These spatially variable RMSLR scenarios were then incorporated into a high-resolution storm surge model using elevated present-day water depths to solve for coupled tide–surge–wave processes. The performance of the model was validated using in situ measurements of astronomical tides, storm tides and ocean waves. Due to the significant variability in the spatial distribution of future relative mean sea level trends in the Yellow Sea, the simplified, uniform RMSLR scenario was found to alter the responses of storm surges. The amplification or attenuation of surge heights was not solely affected by the magnitude of sea level change itself, but also modulated by changing tidal ranges and waves due to SLR. The amplification effects of tidal ranges and nonlinearities within radial sand ridges in the south Yellow Sea tended to be underestimated under the uniform scenario, suggesting that the impacts of SLR on storm surges in this region may represent underestimates.

Is the online global mean sea level information reliable

The purpose of the work is to assess the reliability of satellite altimeter global mean sea level information through consistency, with other products such as ocean temperatures from thermometers or relative mean sea level records from tidal gauges, and stability of the proposed time series. The satellite altimeter global mean sea level is a mostly computational product. The result is unstable, as characterised by significant changes for the past results introduced in subsequent reconstructions. The result is conflicting with the measurements of ocean temperature, which indicates a smaller thermal expansion contribution. The result also is conflicting with the tide gauge records indicating local sea level stability.

Evidence of climate-driven changes on atmospheric, hydrological, and oceanographic variables along the Chilean coastal zone

The Chilean coastal zone (CCZ) is subjected to a complex spectrum of anthropogenic, geophysical, biogeochemical, and climate-driven perturbations. Potentially affected variables including atmospheric sea level pressure (Pa), alongshore wind, sea surface temperature (SST), chlorophyll-a, rainfall, river discharge, relative mean sea level (RMSL), and wave climate are studied using in situ and satellite records, hindcasts, and reanalysis datasets. Linear temporal trends and correlations of anomalies are estimated between 18°S and 55°S along the CCZ. The comparison of some of the variables is achieved by means of a strict homogenization procedure on a monthly basis for 35 years. Our findings show that the poleward drift and strengthening of the Southeast Pacific Subtropical Anticyclone (SPSA) partially explains the increase in Pa and reduction in rainfall and river discharge. The enhancement of alongshore winds, also attributable to changes in the SPSA, increases coastal upwelling, which in turn could reduce SST and increase chlorophyll-a. Despite differential latitudinal responses, increasing wave heights and a southward rotation are evidenced. RMSL does not show significant variation as it is presumably affected by seafloor changes during the seismic cycle. Though some correlations are evidenced, the influence of climate variability at decadal scale (PDO, SAM) may be affecting the detected trends due to the short length of available data. Impacts on coastal communities, infrastructure, and ecosystems are discussed, aiming to highlight that coastal vulnerabilities and risk management should be based on the cumulative impacts of these variables.

Early Holocene tidal flat evolution in a western embayment of East China Sea, in response to sea level rise episodes

The tidal flat in the coastal region of the East China Sea between the Yangtze estuary and Hangzhou Bay in China, interlinked with sediment transport/dispersal and sea level changes since the Last Glacial Maximum, has been a matter of rigorous research for decades. Here we focused on the evolution of the tidal flat at the westernmost extend of former marine influence in response to early Holocene sea level rise. We used sediment composition, ostracods, minerals, organic matter and carbonate contents in combination with endmember modelling analyses and principal component analysis from two sediment cores and an archaeological site close to the western boundary of former marine influence north of the Hangzhou city. The tidal flats at these sites were very sensitive to morphological changes and to sea level variation during the early Holocene. Our data show two major phases of tidal flat formation: i) an early formation stage (9.5–8.0 cal ka BP) with low sediment supply and related slow-down of the mean relative sea level rise (MRSL), followed by ii) the expansion phase with increased sediment supply, storm occurrence as well as fast depositional processes (8.0–7.5 cal ka BP) under a strong MRSL rise close to its present level. A stillstand/decline of MRSL was recorded for the last episodes (7.6–7.5 cal ka BP). The inferences match previously published local to regional sea level curves but differ from the global and modelled regional ones. We propose a connection with early Holocene unstable climatic conditions with intensified storm events and stronger variations in summer monsoon rainfall that affected river discharge and related sediment transport to the inner shelf of the East China Sea between 9.5 and 7.6 cal ka BP. Sedimentary sequences of bayhead areas in tidally-drowned coastal embayments are sensitive to sea level rise episodes and the relevant climate changes.

An inter-comparison of Arctic synoptic scale storms between four global reanalysis datasets

The Arctic is becoming more accessible as sea ice extent continues to decline, resulting in higher human exposure to Arctic storms. This study compares Arctic storm characteristics between the ECMWF-Interim Reanalysis, 55-year Japanese Reanalysis, NASA-Modern Era Retrospective Analysis for Research and Applications Version 2 and National Centre for Environmental Prediction-Climate Forecast System Reanalysis datasets between 1980 and 2017, in winter (DJF) and summer (JJA). It is shown that Arctic storm characteristics are sensitive to the variable used for storm tracking. Arctic storm frequency is found to be similar in summer and winter when using sea level pressure minima to track Arctic storms, whereas, the storm frequency is found to be higher in winter than summer when using 850 hPa relative vorticity to track storms, based on using the same storm tracking algorithm. It is also found that there are no significant trends in Arctic storm characteristics between 1980 and 2017. Given the sparsity of observations in the Arctic, it might be expected that there are large differences in Arctic storm characteristics between the reanalysis datasets. Though, some similar Arctic storm characteristics are found between the reanalysis datasets, it is found that the differences in Arctic storm characteristics between the reanalysis datasets are generally higher in winter than in summer. Overall, the results show that there are differences in Arctic storm characteristics between reanalysis datasets, but even larger differences can arise between using 850 hPa relative vorticity or mean sea level pressure as the storm tracking variable, which adds to the uncertainty associated with current Arctic storm characteristics.

Glacial Isostatic Adjustment, Intraplate Strain, and Relative Sea Level Changes in the Eastern United States

AbstractDetermining the motion of the North American plate is difficult due to horizontal intraplate deformation, caused mainly by glacial isostatic adjustment (GIA) in the parts of the plate that are not deforming tectonically. Determination of plate motions also depends on whether the geocenter of the geodetic reference frame coincides with the center of plate rotation. Any difference/error in the International Terrestrial Reference Frame geocenter will introduce an apparent deformation of the plate. We address the plate rotation and what correction models can best account for this internal deformation. We use continuous GPS sites located far from active tectonic boundaries to derive the velocity field in the eastern United States with uncertainties based on a colored noise model. We hypothesize that the velocities will be described by a rigid plate model once the deformation due to GIA and any geocenter/plate rotation center errors have been removed. We find the smallest intraplate residuals with both a geocenter correction and the ICE‐6G model applied. We further compare the coastal GPS vertical velocities with mean relative sea level change rate and find a ~1.9 mm/year difference, which matches the long‐term average global sea level change rate from tide gauges. The entire North American plate is deforming when analyzed at the ~1 mm/year level, and there is no instantaneously stable part due to the long‐wavelength GIA deformation. An accurate estimate of plate rotation cannot be determined from a geographic subset of the plate but only by removing the strain component via a GIA model or a simultaneous estimation of the spatially varying strain rate.