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Improved GRACE regional mass balance estimates of the Greenland Ice Sheet cross-validated with the input-output method (discussion paper)

Xu, Z. (author), Schrama, E.J.O. (author), Van der Wal, W. (author), Van den Broeke, M. (author), Enderlin, E.M. (author)

In this study, we use satellite gravimetry data from the Gravity Recovery and Climate Experiment (GRACE) to estimate regional mass changes of the Greenland ice sheet (GrIS) and neighbouring glaciated regions using a least-squares inversion approach. We also consider results from the input-output method (IOM) that quantifies the difference...

journal article 2015

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What causes the trends in Geocenter motion estimates?

Rietbroek, R. (author), Schrama, E.J.O. (author)

journal article 2015

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Identifying water mass depletion in northern Iraq observed by GRACE

Mulder, G. (author), Olsthoorn, T.N. (author), Al-manmi, D.A.M.A. (author), Schrama, E.J.O. (author), Smidt, E.H. (author)

Observations acquired by Gravity Recovery And Climate Experiment (GRACE) mission indicate a mass loss of 146 ± 6 mm equivalent water height (EWH) in northern Iraq between 2007 and 2009. These data are used as an independent validation of lake mass variations and a rainfall-runoff model, which is based on local geology and climate conditions....

journal article 2015

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Effect of GIA models with 3D composite mantle viscosity on GRACE mass balance estimates for Antarctica

Van der Wal, W. (author), Whitehouse, P.L. (author), Schrama, E.J.O. (author)

Seismic data indicate that there are large viscosity variations in the mantle beneath Antarctica. Consideration of such variations would affect predictions of models of Glacial Isostatic Adjustment (GIA), which are used to correct satellite measurements of ice mass change. However, most GIA models used for that purpose have assumed the mantle to...

journal article 2015

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Identifying water mass depletion in Northern Iraq observed by GRACE

Mulder, G. (author), Olsthoorn, T.N. (author), Al-manmi, D.A.M.A. (author), Schrama, E.J.O. (author), Smidt, E.H. (author)

Observations acquired by Gravity Recovery And Climate Experiment (GRACE) mission indicate a mass loss of 31 ± 3 km3 or 130 ± 14 mm in Northern Iraq between 2007 and 2009. This data is used as an independent validation of a hydrologic model of the region including lake mass variations. We developed a rainfall–runoff model for five tributaries of...

journal article 2014

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Antarctic outlet glacier mass change resolved at basin scale from satellite gravity gradiometry

Bouman, J. (author), Fuchs, M. (author), Ivins, E. (author), Van der Wal, W. (author), Schrama, E.J.O. (author), Visser, P.N.A.M. (author), Horwath, M. (author)

The orbit and instrumental measurement of the Gravity Field and Steady State Ocean Circulation Explorer (GOCE) satellite mission offer the highest ever resolution capabilities for mapping Earth's gravity field from space. However, past analysis predicted that GOCE would not detect changes in ice sheet mass. Here we demonstrate that GOCE gravity...

journal article 2014

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A mascon approach to assess ice sheet and glacier mass balances and their uncertainties from GRACE data

Schrama, E.J.O. (author), Wouters, B. (author), Rietbroek, R. (author)

The purpose of this paper is to assess the mass changes of the Greenland Ice Sheet (GrIS), Ice Sheets over Antarctica, and Land glaciers and Ice Caps with a global mascon method that yields monthly mass variations at 10,242 mascons. Input for this method are level 2 data from the Gravity Recovery and Climate Experiment (GRACE) system collected...

journal article 2014

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Antarctic contribution to sea level rise observed by GRACE with improved GIA correction

Ivins, E.R. (author), James, T.S. (author), Wahr, J. (author), Schrama, E.J.O. (author), Landerer, F.W. (author), Simon, K.M. (author)

Antarctic volume changes during the past 21 thousand years are smaller than previously thought, and here we construct an ice sheet history that drives a forward model prediction of the glacial isostatic adjustment (GIA) gravity signal. The new model, in turn, should give predictions that are constrained with recent uplift data. The impact of the...

journal article 2013

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GOCE level 2 gravity gradients

Bouman, J. (author), Fiorot, S. (author), Fuchs, M. (author), Gruber, T. (author), Schrama, E.J.O. (author), Tscherning, C.C. (author), Veicherts, M. (author), Visser, P.N.A.M. (author)

Two of the GOCE Level 2 products are the gravity gradients (GGs) in the Gradiometer Reference Frame (GRF) and the GGs in the Local North-Oriented Frame (LNOF). The GRF is an instrument frame and the GGs are derived from the L1b GGs. The L1b to L2 GG processing involves corrections for temporal gravity variations, outlier detection and data gap...

conference paper 2011

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GOCE gravitational gradients along the orbit

Bouman, J. (author), Fiorot, S. (author), Fuchs, M. (author), Gruber, T. (author), Schrama, E.J.O. (author), Tscherning, C. (author), Veicherts, M. (author), Visser, P.N.A.M. (author)

GOCE is ESA’s gravity field mission and the first satellite ever that measures gravitational gradients in space, that is, the second spatial derivatives of the Earth’s gravitational potential. The goal is to determine the Earth’s mean gravitational field with unprecedented accuracy at spatial resolutions down to 100 km. GOCE carries a gravity...

journal article 2011

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Present Day Regional Mass Loss of Greenland Observed with Satellite Gravimetry

Schrama, E.J.O. (author), Wouters, B. (author), Vermeersen, L.L.A. (author)

This paper summarizes results obtained for Greenland’s mass balance observed with NASA’s GRACE mission. We estimate a Greenland ice sheet mass loss at ?201 ± 19 Gt/year including a discernible acceleration of ?8 ± 7 Gt/year2 between March 2003 and February 2010. The mass loss of glacier systems on the South East of Greenland has slowed down...

journal article 2011

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Revisiting Greenland ice sheet mass loss observed by GRACE

Schrama, E.J.O. (author), Wouters, B. (author)

In this paper we discuss a new method for determining mass time series for 16 hydrological basins representing the Greenland system (GS) whereby we rely on Gravity Recovery and Climate Experiment (GRACE) mission data. In the same analysis we also considered observed mass changes over Ellesmere Island, Baffin Island, Iceland, and Svalbard (EBIS)....

journal article 2011

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Dependency of resolvable gravitational spatial resolution on space-borne observation techniques

Visser, P.N.A.M. (author), Schrama, E.J.O. (author), Sneeuw, N. (author), Weigelt, M. (author)

The so-called Colombo-Nyquist (Colombo, The global mapping of gravity with two satellites, 1984) rule in satellite geodesy has been revisited. This rule predicts that for a gravimetric satellite flying in a (near-)polar circular repeat orbit, the maximum resolvable geopotential spherical harmonic degree (lmax) is equal to half the number of...

conference paper 2009

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Preprocessing of gravity gradients at the GOCE high-level processing facility

Bouman, J. (author), Rispens, S. (author), Gruber, T. (author), Koop, R. (author), Schrama, E. (author), Visser, P. (author), Tscherning, C.C. (author), Veicherts, M. (author)

One of the products derived from the gravity field and steady-state ocean circulation explorer (GOCE) observations are the gravity gradients. These gravity gradients are provided in the gradiometer reference frame (GRF) and are calibrated in-flight using satellite shaking and star sensor data. To use these gravity gradients for application in...

journal article 2008

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GRACE observes small?scale mass loss in Greenland

Wouters, B. (author), Chambers, D. (author), Schrama, E.J.O. (author)

Using satellite gravity data between February 2003 and January 2008, we examine changes in Greenland's mass distribution on a regional scale. During this period, Greenland lost mass at a mean rate of 179 ± 25 Gt/yr, equivalent to a global mean sea level change of 0.5 ± 0.1 mm/yr. Rates increase over time, suggesting an acceleration of the mass...

journal article 2008

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Improved accuracy of GRACE gravity solutions through empirical orthogonal function filtering of spherical harmonics

Wouters, B. (author), Schrama, E.J.O. (author)

One of the major problems one has to deal with when working with Gravity Recovery and Climate Experiment (GRACE) data is the increasing error spectrum at higher degrees in the provided Stokes coefficients, appearing as unphysical North?South striping patterns in the maps of equivalent water height (EWH). This phenomenon is commonly suppressed by...

journal article 2007

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Signal and noise in Gravity Recovery and Climate Experiment (GRACE) observed surface mass variations

Schrama, E.J.O. (author), Wouters, B. (author), Lavallée, D.A. (author)

The Gravity Recovery and Climate Experiment (GRACE) product used for this study consists of 43 monthly potential coefficient sets released by the GRACE science team which are used to generate surface mass thickness grids expressed as equivalent water heights (EQWHs). We optimized both the smoothing radius and the level of approximation by...

journal article 2007

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Analysis and modeling of the seasonal South China Sea temperature cycle using remote sensing

Twigt, D.J. (author), De Goede, E.D. (author), Schrama, E.J.O. (author), Gerritsen, H. (author)

journal article 2007

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Accuracy assessment of the monthly GRACE geoids based upon a simulation

Schrama, E.J.O. (author), Visser, P.N.A.M. (author)

journal article 2007

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‘DEOS CHAMP-01C 70’: A model of the Earth’s gravity field computed from accelerations of the CHAMP satellite

Ditmar, P.G. (author), Kuznetsov, V. (author), Van Eck van der Sluis, A.A. (author), Schrama, E. (author), Klees, R. (author)

Performance of a recently proposed technique for gravity field modeling has been assessed with data from the CHAMP satellite. The modeling technique is a variant of the acceleration approach. It makes use of the satellite accelerations that are derived from the kinematic orbit with the 3-point numerical differentiation scheme. A 322-day data set...

journal article 2005