/pdf/extending-the-global-mass-change-data-record-grace-follow-on-35cmy02xau.pdf

Extending the Global Mass Change Data Record: GRACE Follow-On Instrument and Science Data Performance

Between 2003-2016, the Greenland ice sheet (GrIS) was one of the largest contributors to sea level rise, as it lost about 255 Gt of ice per year. This mass loss slowed in 2017 and 2018 to about 100 Gt yr−1. Here we examine further changes in rate of GrIS mass loss, by analyzing data from the GRACE-FO (Gravity Recovery and Climate Experiment – Follow On) satellite mission, launched in May 2018. Using simulations with regional climate models we show that the mass losses observed in 2017 and 2018 by the GRACE and GRACE-FO missions are lower than in any other two year period between 2003 and 2019, the combined period of the two missions. We find that this reduced ice loss results from two anomalous cold summers in western Greenland, compounded by snow-rich autumn and winter conditions in the east. For 2019, GRACE-FO reveals a return to high melt rates leading to a mass loss of 223 ± 12 Gt month−1 during the month of July alone, and a record annual mass loss of 532 ± 58 Gt yr−1. Mass loss from the Greenland ice sheet returned to record levels in 2019, following unusually small loss in 2017-18, according to an analysis of satellite data from GRACE and its follow-on mission GRACE-FO.

/pdf/return-to-rapid-ice-loss-in-greenland-and-record-loss-in-2jrnfrrwvw.pdf

Return to rapid ice loss in Greenland and record loss in 2019 detected by the GRACE-FO satellites

GFZ GRACE Level-2 Processing Standards Document for Level-2 Product Release 0005

Ocean-driven basal melting of Antarctica's floating ice shelves accounts for about half of their mass loss in steady-state, where gains in ice shelf mass are balanced by losses. Ice shelf thickness changes driven by varying basal melt rates modulate mass loss from the grounded ice sheet and its contribution to sea level, and the changing meltwater fluxes influence climate processes in the Southern Ocean. Existing continent-wide melt rate datasets have no temporal variability, introducing uncertainties in sea level and climate projections. Here, we combine surface height data from satellite radar altimeters with satellite-derived ice velocities and a new model of firn-layer evolution to generate a high-resolution map of time-averaged (2010-2018) basal melt rates, and time series (1994-2018) of meltwater fluxes for most ice shelves. Total basal meltwater flux in 1994 (1090±150 Gt/yr) was not significantly different from the steady-state value (1100±60 Gt/yr), but increased to 1570±140 Gt/yr in 2009, followed by a decline to 1160±150 Gt/yr in 2018. For the four largest "cold-water" ice shelves we partition meltwater fluxes into deep and shallow sources to reveal distinct signatures of temporal variability, providing insights into climate forcing of basal melting and the impact of this melting on the Southern Ocean.

/pdf/interannual-variations-in-meltwater-input-to-the-southern-4slwdtv474.pdf

Interannual variations in meltwater input to the Southern Ocean from Antarctic ice shelves

. The International Centre for Global Earth Models (ICGEM,
 http://icgem.gfz-potsdam.de/ , last access: 6 May 2019) hosted at the
GFZ German Research Centre for Geosciences (GFZ) is one of the five services
coordinated by the International Gravity Field Service (IGFS) of the
International Association of Geodesy (IAG). The goal of the ICGEM service is
to provide the scientific community with a state-of-the-art archive of static
and temporal global gravity field models of the Earth, and develop and
operate interactive calculation and visualization services of gravity field
functionals on user-defined grids or at a list of particular points via its
website. ICGEM offers the largest collection of global gravity field models,
including those from the 1960s to the 1990s, as well as the most recent ones,
which have been developed using data from dedicated satellite gravity
missions, CHAMP, GRACE, GOCE, advanced processing methodologies, and
additional data sources such as satellite altimetry and terrestrial gravity.
The global gravity field models have been collected from different
institutions at international level and after a validation process made
publicly available in a standardized format with DOI numbers assigned through
GFZ Data Services. The development and maintenance of such a unique platform
is crucial for the scientific community in geodesy, geophysics, oceanography,
and climate research. In this article, we present the development history and
future plans of ICGEM and its current products and essential services. We
present the ICGEM's data by means of Earth's static, temporal, and
topographic gravity field models as well as the gravity field models of other
celestial bodies together with examples produced by the ICGEM's calculation
and 3-D visualization services and give an insight into how the ICGEM service
can additionally contribute to the needs of research and society.

/pdf/icgem-15-years-of-successful-collection-and-distribution-of-30zzdralnf.pdf

ICGEM – 15 years of successful collection and distribution of global gravitational models, associated services, and future plans

EIGEN-6C3 - The latest Combined Global Gravity Field Model including GOCE data up to degree and order 1949 of GFZ Potsdam and GRGS Toulouse

GFZ Potsdam and GRGS Toulouse have a long-time close cooperation in the field of global gravity field determination. Here we focus on (1) GOCE gravity field determination and (2) computation of high resolution combined gravity field models. Such data products play a fundamental role in geodesy and Earth sciences, ranging from practical purposes, like precise orbit determination, to scientific applications, like investigations of the density structure of the Earth’s interior. Here we present our combined gravity field model EIGEN-6C4 which is the fourth release of EIGEN-6C (EIGEN = European Improved Gravity model of the Earth by New techniques).

EIGEN-6C4 - The latest combined global gravity field model including GOCE data up to degree and order 1949 of GFZ Potsdam and GRGS Toulouse

High-resolution global gravity field models play a fundamental role in geodesy and Earth sciences, ranging from practical purposes, like precise orbit determination, to scientific applications, like investigations of the density structure of the Earth’s interior. We report on the latest combined EIGEN-model (EIGEN = European Improved Gravity model of the Earth by New techniques), which is complete to degree and order 1440 and was jointly elaborated by GFZ Potsdam and CNES/GRGS Toulouse. It is the first EIGEN model inferred from a combination of GRACE and GOCE data , enhanced with the DTU10 surface gravity data.

EIGEN-6 – A new combined global gravity field model including GOCE data from the collaboration of GFZ Potsdam and GRGS Toulouse

Time-variable gravity field models derived from observations of the Gravity Recovery and Climate Experiment (GRACE) mission, whose science operations phase ended in June 2017 after more than 15 years, enabled a multitude of studies of Earth’s surface mass transport processes and climate change. The German Research Centre for Geosciences (GFZ), routinely processing such monthly gravity fields as part of the GRACE Science Data System, has reprocessed the complete GRACE mission and released an improved GFZ GRACE RL06 monthly gravity field time series. This study provides an insight into the processing strategy of GFZ RL06 which has been considerably changed with respect to previous GFZ GRACE releases, and modifications relative to the precursor GFZ RL05a are described. The quality of the RL06 gravity field models is analyzed and discussed both in the spectral and spatial domain in comparison to the RL05a time series. All results indicate significant improvements of about 40% in terms of reduced noise. It is also shown that the GFZ RL06 time series is a step forward in terms of consistency, and that errors of the gravity field coefficients are more realistic. These findings are confirmed as well by independent validation of the monthly GRACE models, as done in this work by means of ocean bottom pressure in situ observations and orbit tests with the GOCE satellite. Thus, the GFZ GRACE RL06 time series allows for a better quantification of mass changes in the Earth system.

/pdf/the-gfz-grace-rl06-monthly-gravity-field-time-series-1u3fx8d6pl.pdf

The GFZ GRACE RL06 Monthly Gravity Field Time Series: Processing Details and Quality Assessment

ESA's Release 6 GOCE gravity field model by means of the direct approach based on improved filtering of the reprocessed gradients of the entire mission (GO_CONS_GCF_2_DIR_R6)

Oleh Abrykosov

Papers

EIGEN-6C3 - The latest Combined Global Gravity Field Model including GOCE data up to degree and order 1949 of GFZ Potsdam and GRGS Toulouse

EIGEN-6C4 - The latest combined global gravity field model including GOCE data up to degree and order 1949 of GFZ Potsdam and GRGS Toulouse

EIGEN-6 – A new combined global gravity field model including GOCE data from the collaboration of GFZ Potsdam and GRGS Toulouse

The GFZ GRACE RL06 Monthly Gravity Field Time Series: Processing Details and Quality Assessment

ESA's Release 6 GOCE gravity field model by means of the direct approach based on improved filtering of the reprocessed gradients of the entire mission (GO_CONS_GCF_2_DIR_R6)