A Rossby whistle: a resonant basin mode observed in the Caribbean Sea

We show that an important source of coastal sea level variability around the Caribbean Sea is a resonant basin mode. The mode consists of a baroclinic Rossby wave which propagates westward across the basin and is rapidly returned to the east along the southern boundary as coastal shelf waves. Almost two wavelengths of the Rossby wave fit across the basin, and it has a period of 120 days. The porous boundary of the Caribbean Sea results in this mode exciting a mass exchange with the wider ocean, leading to a dominant mode of bottom pressure variability which is almost uniform over the Grenada, Venezuela, and Colombia basins and has a sharp spectral peak at 120 day period. As the Rossby waves have been shown to be excited by instability of the Caribbean Current, this resonant mode is dynamically equivalent to the operation of a whistle

Ocean mass, sterodynamic effects, and vertical land motion largely explain US coast relative sea level rise

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Harvey, T., Hamlington, B. D., Frederikse, T., Nerem, R. S., Piecuch, C. G., Hammond, W. C., Blewitt, G., Thompson, P. R., Bekaert, D. P. S., Landerer, F. W., Reager, J. T., Kopp, R. E., Chandanpurkar, H., Fenty, I., Trossman, D. S., Walker, J. S., & Boening, C. W. Ocean mass, sterodynamic effects, and vertical land motion largely explain US coast relative sea level rise. Communications Earth & Environment, 2(1), (2021): 233, https://doi.org/10.1038/s43247-021-00300-w.Regional sea-level changes are caused by several physical processes that vary both in space and time. As a result of these processes, large regional departures from the long-term rate of global mean sea-level rise can occur. Identifying and understanding these processes at particular locations is the first step toward generating reliable projections and assisting in improved decision making. Here we quantify to what degree contemporary ocean mass change, sterodynamic effects, and vertical land motion influence sea-level rise observed by tide-gauge locations around the contiguous U.S. from 1993 to 2018. We are able to explain tide gauge-observed relative sea-level trends at 47 of 55 sampled locations. Locations where we cannot explain observed trends are potentially indicative of shortcomings in our coastal sea-level observational network or estimates of uncertainty.The research was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. C.G.P. was supported by NASA grant 80NSSC20K1241. B.D.H., T.C.H., and T.F. were supported by NASA JPL Task 105393.281945.02.25.04.59. R.E.K. and J.S.W. were supported by U.S. National Aeronautics and Space Administration (grants 80NSSC17K0698, 80NSSC20K1724 and JPL task 105393.509496.02.08.13.31) and U.S. National Science Foundation (grant ICER-1663807). P.R.T. acknowledges financial support from the NOAA Global Ocean Monitoring and Observing program in support of the University of Hawaii Sea Level Center (NA11NMF4320128). The ECCO project is funded by the NASA Physical Oceanography; Modeling, Analysis, and Prediction; and Cryosphere Programs

A Record-High Ocean Bottom Pressure in the South Pacific Observed by GRACE

No abstract availabl

Combination Service for Time-variable Gravity Field Solutions (COST-G) - current status

In the frame of the European Gravity Service for Improved Emergency Management (EGSIEM), a prototype service was established to combine monthly gravity field solutions from the past US- German GRACE mission in order to deliver improved gravity field solutions for applications in Earth and environmental science research. This prototype now is in transition to the Combination Service for Time-variable Gravity Field Solutions (COST-G), a Product Center of the International Gravity Field Service (IGFS) of the International Association of Geodesy (IAG). We report on the achievements made so far and the transition of the prototype phase into regular operation. We present a comparison, validation and combination of the latest GRACE gravity field time-series of different GRACE processing centers, based on recent RL03 Level-1B GRACE observation data as well as updated background models and processing standards. A focus is laid on the effect of different background modeling strategies on the resulting gravity field models and the relative weights determined by Variance Component Estimation on solution level

COST-G: The new International Combination Service for Time-variable Gravity Field Solutions of the IAG/IGFS

COST-G is the new combination service for time-variable gravity field solutions of the International Association of Geodesy (IAG). In the frame of COST-G monthly GRACE (and in the future GRACE-FO) gravity fields of all associated analysis centers undergo - strict quality control to guarantee correct signal content, - careful noise assessment to derive relative weights, - combination on normal equation level to correctly consider all correlations, and - transformation of the combined gravity fields into user-friendly L3-products, to provide to the users unique, robust and reliable gravity field solutions that profit from reduced noise compared to the individual contributions. We apply the mechanisms of quality control and noise assessment of COST-G to the new GRACE-RL06 time-series and compare to RL05 and to alternative time-series provided in the frame of the European Gravity Service for Improved Emergency Management (EGSIEM)

Exploration of Antarctic Ice Sheet 100-year contribution to sea level rise and associated model uncertainties using the ISSM framework

Estimating the future evolution of the Antarctic Ice Sheet (AIS) is critical for improving future sea level rise (SLR) projections. Numerical ice sheet models are invaluable tools for bounding Antarctic vulnerability; yet, few continental-scale projections of century-scale AIS SLR contribution exist, and those that do vary by up to an order of magnitude. This is partly because model projections of future sea level are inherently uncertain and depend largely on the model's boundary conditions and climate forcing, which themselves are unknown due to the uncertainty in the projections of future anthropogenic emissions and subsequent climate response. Here, we aim to improve the understanding of how uncertainties in model forcing and boundary conditions affect ice sheet model simulations. With use of sampling techniques embedded within the Ice Sheet System Model (ISSM) framework, we assess how uncertainties in snow accumulation, ocean-induced melting, ice viscosity, basal friction, bedrock elevation, and the presence of ice shelves impact continental-scale 100-year model simulations of AIS future sea level contribution. Overall, we find that AIS sea level contribution is strongly affected by grounding line retreat, which is driven by the magnitude of ice shelf basal melt rates and by variations in bedrock topography. In addition, we find that over 1.2 m of AIS global mean sea level contribution over the next century is achievable, but not likely, as it is tenable only in response to unrealistically large melt rates and continental ice shelf collapse. Regionally, we find that under our most extreme 100-year warming experiment generalized for the entire ice sheet, the Amundsen Sea sector is the most significant source of model uncertainty (1032 mm 6σ spread) and the region with the largest potential for future sea level contribution (297 mm). In contrast, under a more plausible forcing informed regionally by literature and model sensitivity studies, the Ronne basin has a greater potential for local increases in ice shelf basal melt rates. As a result, under this more likely realization, where warm waters reach the continental shelf under the Ronne ice shelf, it is the Ronne basin, particularly the Evans and Rutford ice streams, that are the greatest contributors to potential SLR (161 mm) and to simulation uncertainty (420 mm 6σ spread)

Mezinárodní unie geodézie a geofyziky (IUGG)

Příručka geodetů je vydávána Mezinárodní asociací geodézie (IAG) pravidelně po každém Valném shromáždění IUGG / IAG. Cílem je představit současnou strukturu IAG a její specifikace a seznámit širokou geodetickou komunitu s působností a pracovníky složek asociace pro nadcházející legislativní období. Vědecký program a plánované činnosti jsou podrobně popsány. První část příručky 2020 představuje historický vývoj a současné předpisy IAG (stanovy, stanovy a pravidla revidované během Valného shromáždění IUGG / IAG 2019). Druhá část shrnuje výsledky Valného shromáždění IAG konaného ve spojení s 27. Valným shromážděním IUGG v kanadském Montrealu v červenci 2019. Přehled nejdůležitějších výsledků IAG od roku 2015 do roku 2019 je uveden v projevu prezidenta. Publikovány jsou citace vědců vyznamenaných v Montrealu nejvyššími oceněními IAG (Levalloisova medaile, Cena Guy Bomforda a Cena mladých autorů). Tento oddíl uzavírají zprávy generálního tajemníka, zasedání Rady a výkonného výboru IAG a rezoluce IUGG a IAG. Třetí část příručky obsahuje podrobné struktury a programy na období 2019--2023. Všechny komponenty IAG (komise, mezikomisní výbor, komunikační a terénní pobočka, služby a globální geodetický pozorovací systém) jsou prezentovány spolu s jejich dílčími složkami (subkomise, projekty, studijní skupiny a pracovní skupiny). Tato část popisuje plánovanou vědeckou práci IAG v následujících letech. Čtvrtá část doplňuje příručku o některé obecné informace užitečné pro geodetickou komunitu. Zvýrazněno je internetové zastoupení IAG a publikační řada a jsou zde uvedeny národní delegáti a zástupci IAG pro služby a mezinárodní vědecké orgány.The Geodesist’s Handbook is published by the International Association of Geodesy (IAG) periodically after each IUGG/IAG General Assembly. The objective is to present the current IAG structure and its specifications, and to introduce the terms of reference and the officers of the Association’s components for the upcoming legislative period to the broad geodetic community. The scientific program and planned activities are described in detail. The first part of the Handbook 2020 presents the historical developments and current regulations of the IAG (Statutes, Bylaws and Rules as reviewed during the IUGG/IAG General Assembly 2019). The second part summarises the outcome of the IAG General Assembly held in conjunction with the 27th IUGG General Assembly in Montreal, Canada, in July 2019. An overview of the most important IAG results from 2015 to 2019 is given in the presidential address. The citations of thescientists decorated in Montreal with the highest IAG awards (Levallois Medal, Guy Bomford Prize, and Young Authors Award) are published. Reports of the Secretary General, the IAG Council and Executive Committee meetings, and the IUGG and IAG resolutions conclude this section. The third part of the Handbook contains the detailed structures and programs for the period 2019-2023. All IAG components (Commissions, Inter-commission Committee, Communication and Outreach Branch, Services, and the Global Geodetic Observing System) are presented along with their sub-components (Sub-commissions, Projects, Study Groups and Working Groups). This part describes the planed scientific work of IAG during the coming years. The fourth part completes the Handbook with some general information useful for the geodetic community. The IAG Internet representation and the publication series are highlighted, and the IAG national delegates and representatives to services and international scientific bodies are listed

Contributions of GRACE to understanding climate change

Time-resolved satellite gravimetry has revolutionized understanding of mass transport in the Earth system. Since 2002, the Gravity Recovery and Climate Experiment (GRACE) has enabled monitoring of the terrestrial water cycle, ice sheet and glacier mass balance, sea level change and ocean bottom pressure variations and understanding responses to changes in the global climate system. Initially a pioneering experiment of geodesy, the time-variable observations have matured into reliable mass transport products, allowing assessment and forecast of a number of important climate trends and improve service applications such as the U.S. Drought Monitor. With the successful launch of the GRACE Follow-On mission, a multi decadal record of mass variability in the Earth system is within reach