Increasing rates of ice mass loss from the Greenland and Antarctic ice sheets revealed by GRACE

Velicogna, I.

doi:10.1029/2009gl040222

Cited by 629 publications

(476 citation statements)

References 23 publications

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“…In particular, we studied the two most prominent regions where variations can be expected: the Amazon River basin, which exhibits the highest annual variations due to the changing water content; and Greenland, which also exhibits annual variation, but more importantly features the biggest trend in terms of mass change. This trend is due to the massive ice loss caused by the global climate change (Velicogna 2009;Cazenave and Chen 2010).…”

Section: Gravity Field Resultsmentioning

confidence: 99%

Precise orbit determination based on raw GPS measurements

Zehentner

Mayer‐Gürr

2015

J Geod

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Precise orbit determination is an essential part of the most scientific satellite missions. Highly accurate knowledge of the satellite position is used to geolocate measurements of the onboard sensors. For applications in the field of gravity field research, the position itself can be used as observation. In this context, kinematic orbits of low earth orbiters (LEO) are widely used, because they do not include a priori information about the gravity field. The limiting factor for the achievable accuracy of the gravity field through LEO positions is the orbit accuracy. We make use of raw global positioning system (GPS) observations to estimate the kinematic satellite positions. The method is based on the principles of precise point positioning. Systematic influences are reduced by modeling and correcting for all known error sources. Remaining effects such as the ionospheric influence on the signal propagation are either unknown or not known to a sufficient level of accuracy. These effects are modeled as unknown parameters in the estimation process. The redundancy in the adjustment is reduced; however, an improvement in orbit accuracy leads to a better gravity field estimation. This paper describes our orbit determination approach and its mathematical background. Some examples of real data applications highlight the feasibility of the orbit determination method based on raw GPS measurements. Its suitability for gravity field estimation is presented in a second step. B Norbert Zehentner

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Section: Gravity Field Resultsmentioning

confidence: 99%

Precise orbit determination based on raw GPS measurements

Zehentner

Mayer‐Gürr

2015

J Geod

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“…Wingham et al, 1998;Shepherd et al, 2001 andZwally et al, 2005) and from gravity measurements (e.g. Velicogna, 2009), these methods do not distinguish ice dynamics and accumulation fluctuations which may introduce errors in mass balance estimates.…”

Section: Introductionmentioning

confidence: 99%

Spatially extensive estimates of annual accumulation in the dry snow zone of the Greenland Ice Sheet determined from radar altimetry

et al. 2010

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Abstract. We present estimates of accumulation rate along a 200 km transect ranging in elevation from 2750 to 3150 m in the dry snow zone on the western slope of the Greenland Ice Sheet. An airborne radar altimeter is used to estimate the thickness of annual internal layers and, in conjunction with ground based snow/firn density profiles, annual accumulation rates between 1998 and 2003 are derived. A clear gradient in the thickness of each layer observed by the radar altimeter and in the associated estimates of annual accumulation is seen along the transect, with a 33.6%± 16% mean decrease in accumulation from west to east. The observed inter-annual variability is high, with the annual mean accumulation rate estimated at 0.359 m.w.e. yr −1 (s.d. ± 0.049 m.w.e. yr −1 ). Mean accumulation rates modelled using meteorological models overestimate our results by 16% on average, but by 32% and 42% in the years 2001 and 2002. The methodology presented here demonstrates the potential to obtain accurate and spatially extensive accumulation rates from radar altimeters in regions of ice sheets where field observations are sparse, and accumulation rates greater than several tens of cm.

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“…Recent observations show an accelerated ice loss of the Greenland ice sheet (Velicogna, 2009;Rignot and others, 2011) during the past few decades, attributed to both changes in surface mass balance and ice dynamics (Howat and others, 2007;Rignot and others, 2011). Retreat of outlet glaciers is observed all around the periphery of the Greenland ice sheet; however, the acceleration has a high temporal and spatial variability (McFadden and others, 2011;Moon and others, 2012).…”

Section: Introductionmentioning

confidence: 99%

A fast Newton–Krylov solver for seasonally varying global ocean biogeochemistry models

Primeau

2008

Ocean Modelling

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A fast Newton-Krylov solver for seasonally varying global ocean biogeochemistry models ABSTRACT. Observations show that the Greenland ice sheet has been losing mass at an increasing rate over the past few decades, which makes it a major contributor to sea-level rise. Here we use a threedimensional higher-order ice-flow model, adaptive mesh refinement and inverse methods to accurately reproduce the present-day ice flow of the Greenland ice sheet. We investigate the effect of the ice thermal regime on (1) basal sliding inversion and (2) projections over the next 100 years. We show that steady-state temperatures based on present-day conditions allow a reasonable representation of the thermal regime and that both basal conditions and century-scale projections are weakly sensitive to small changes in the initial temperature field, compared with changes in atmospheric conditions or basal sliding. We conclude that although more englacial temperature measurements should be acquired to validate the models, and a better estimation of geothermal heat flux is needed, it is reasonable to use steady-state temperature profiles for short-term projections, as external forcings remain the main drivers of the changes occurring in Greenland.

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Increasing rates of ice mass loss from the Greenland and Antarctic ice sheets revealed by GRACE

Cited by 629 publications

References 23 publications

Precise orbit determination based on raw GPS measurements

Precise orbit determination based on raw GPS measurements

Spatially extensive estimates of annual accumulation in the dry snow zone of the Greenland Ice Sheet determined from radar altimetry

A fast Newton–Krylov solver for seasonally varying global ocean biogeochemistry models

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