A global assessment of accelerations in surface mass transport

Wu, Xiaoping; Heflin, M. B.

doi:10.1002/2015gl064941

Cited by 10 publications

(10 citation statements)

References 21 publications

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“…Analysis of 13 years (2002-2015) of data from GRACE, Global Navigation Satellite System, satellite laser ranging and the Ocean Circulation and Climate of the ocean bottom pressure [39] give an acceleration of global mass (non-steric) component of 0.04±0.09 mm year −2 , similar to the above satellite altimeter estimate (for latitudes less than 65°) but with larger uncertainty estimates. This ocean mass is the balance between accelerated mass loss from the Greenland and West Antarctic Ice Sheets and increased mass gain in land water storage and parts of East Antarctica, and decreased mass loss from glaciers in Alaska and some other regions.…”

Section: The Satellite Altimeter Periodmentioning

confidence: 53%

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Recent Progress in Understanding and Projecting Regional and Global Mean Sea Level Change

Clark

Church

Gregory

et al. 2015

Curr Clim Change Rep

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Considerable progress has been made in understanding the present and future regional and global sea level in the 2 years since the publication of the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change. Here, we evaluate how the new results affect the AR5's assessment of (i) historical sea level rise, including attribution of that rise and implications for the sea level budget, (ii) projections of the components and of total global mean sea level (GMSL), and (iii) projections of regional variability and emergence of the anthropogenic signal. In each of these cases, new work largely provides additional evidence in support of the AR5 assessment, providing greater confidence in those findings. Recent analyses confirm the twentieth century sea level rise, with some analyses showing a slightly smaller rate before 1990 and some a slightly larger value than reported in the AR5. There is now more evidence of an acceleration in the rate of rise. Ongoing ocean heat uptake and associated thermal expansion have continued since 2000, and are consistent with ocean thermal expansion reported in the AR5. A significant amount of heat is being stored deeper in the water column, with a larger rate of heat uptake since 2000 compared to the previous decades and with the largest storage in the Southern Ocean. The first formal detection studies for ocean thermal expansion and glacier mass loss since the AR5 have confirmed the AR5 finding of a significant anthropogenic contribution to sea level rise over the last 50 years. New projections of glacier loss from two regions suggest smaller contributions to GMSL rise from these regions than in studies assessed by the AR5; additional regional studies are required to further assess whether there are broader implications of these results. Mass loss from the Greenland Ice Sheet, primarily as a result of increased surface melting, and from the Antarctic Ice Sheet, primarily as a result of increased ice discharge, has accelerated. The largest estimates of acceleration in mass loss from the two ice sheets for 2003-2013 equal or exceed the acceleration of GMSL rise calculated from the satellite altimeter sea level record over the longer period of 1993-2014. However, when increased mass gain in land water storage and parts of East Antarctica, and decreased mass loss from glaciers in Alaska and some other regions are taken into account, the net acceleration in the ocean mass gain is consistent with the satellite altimeter record. New studies suggest that a marine ice sheet instability (MISI) may have been initiated in parts of the West Antarctic Ice Sheet (WAIS), but that it will affect only a limited number of ice streams in the twenty-first century. New projections of mass loss from the Greenland and Antarctic Ice Sheets by 2100, including a contribution from parts of WAIS undergoing unstable retreat, suggest a contribution that falls largely within the likely range (i.e., two thirds probability) of the AR5. These new results increase confidence in the AR5 likel...

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Section: The Satellite Altimeter Periodmentioning

confidence: 53%

“…Wu and Heflin [39] also reported increased mass gain in land water storage and parts of East Antarctica, and decreased mass loss from glaciers in Alaska and some other regions such that the acceleration in the ocean mass gain is consistent with the satellite altimeter record.…”

Section: Antarctic Ice Sheetmentioning

confidence: 66%

Recent Progress in Understanding and Projecting Regional and Global Mean Sea Level Change

Clark

Church

Gregory

et al. 2015

Curr Clim Change Rep

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“…To substantiate this assumption, the JTRF‐derived (CM‐CN) offsets have been compared to the geocenter time series (CM‐CF) by Wu and Heflin [] who adopted a spectral inverse approach based on a combination of GNSS station position residuals, monthly detrended Stokes coefficients from Gravity Recovery and Climate Experiment (GRACE), and OBP variations from JPL's ECCO model. The estimation is conducted in the spherical harmonic domain, and the inverted geocenter motion components are inferred from the degree‐1 surface mass distribution and the degree‐1 surface deformation signatures.…”

Section: Jtrf2014 Resultsmentioning

confidence: 99%

“…Superimposed in gray is the (CM‐CN) time series derived from the ILRS input data sets. The green dots are monthly time series of (CM‐CF) obtained from the spectral inversion of GNSS and GRACE data along with modeled OBP variations over the same time span as detailed in [ Wu and Heflin , ]. (right column) The panels show the three different time series in the spectral domain with the same conventions on the color codes.…”

Section: Jtrf2014 Resultsmentioning

confidence: 99%

“…The time‐variable geocentric station coordinates appear to describe the Earth deformation reasonably well during tracking periods and short data gaps. The JTRF2014 unified time series have been used to infer temporal variations of (CM‐CN) offsets which appear to be in very good agreement with the quasi‐independent geocenter motion estimated via spectral inversion of GNSS, GRACE, and ECCO‐derived OBP variations [ Wu and Heflin , ]. If we assume that the geocenter determined via spectral inversion is potentially superior in accessing (CM‐CF) motion, then the utmost level of consistency of JTRF2014‐derived (CM‐CN) with the inverted geocenter can be used as a proxy indicating the high accuracy of JTRF2014.…”

Section: Discussionmentioning

confidence: 99%

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JTRF2014, the JPL Kalman filter and smoother realization of the International Terrestrial Reference System

et al. 2017

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We present and discuss JTRF2014, the Terrestrial Reference Frame (TRF) the Jet Propulsion Laboratory constructed by combining space‐geodetic inputs from very long baseline interferometry (VLBI), satellite laser ranging (SLR), Global Navigation Satellite Systems (GNSS), and Doppler orbitography and radiopositioning integrated by satellite submitted for the realization of ITRF2014. Determined through a Kalman filter and Rauch‐Tung‐Striebel smoother assimilating position observations, Earth orientation parameters, and local ties, JTRF2014 is a subsecular, time series‐based TRF whose origin is at the quasi‐instantaneous center of mass (CM) as sensed by SLR and whose scale is determined by the quasi‐instantaneous VLBI and SLR scales. The dynamical evolution of the positions accounts for a secular motion term, annual, and semiannual periodic modes. Site‐dependent variances based on the analysis of loading displacements induced by mass redistributions of terrestrial fluids have been used to control the extent of random walk adopted in the combination. With differences in the amplitude of the annual signal within the range 0.5–0.8 mm, JTRF2014‐derived center of network‐to‐center of mass (CM‐CN) is in remarkable agreement with the geocenter motion obtained via spectral inversion of GNSS, Gravity Recovery and Climate Experiment (GRACE) observations and modeled ocean bottom pressure from Estimating the Circulation and Climate of the Ocean (ECCO). Comparisons of JTRF2014 to ITRF2014 suggest high‐level consistency with time derivatives of the Helmert transformation parameters connecting the two frames below 0.18 mm/yr and weighted root‐mean‐square differences of the polar motion (polar motion rate) in the order of 30 μas (17 μas/d).

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Does GRACE see the terrestrial water cycle “intensifying”?

et al. 2016

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Several researchers have postulated that, under a changing climate due to anthropogenic forcing, an intensification of the water cycle is already under way. This is usually related to increases in hydrological fluxes as precipitation (P), evapotranspiration (E), and river discharge (R). It is under debate, however, whether such observed or reconstructed flux changes are real and on what scales. Large-scale increase or decrease of the flux deficit (P-E-R), i.e., flux changes that do not compensate, would lead to acceleration or deceleration of water storage anomalies potentially visible in Gravity Recovery and Climate Experiment (GRACE) data. In agreement with earlier studies, we do find such accelerations in global maps of gridded GRACE water storage anomalies over 2003-2012. However, these have been generally associated with interannual and decadal climate variability. Yet we show that even after carefully isolating and removing the contribution of El Niño that partially masks long-term changes, using a new method, accelerations of up to 12 mm/yr 2 remain in regions such as Australia, Turkey, and Northern India. We repeat our analysis with flux fields from two global atmospheric reanalyses that include land surface models (ERA-Interim and MERRA-Land). While agreeing well with GRACE on shorter time scales, they fall short in displaying long-term trends corresponding to GRACE accelerations. We hypothesize that this may be due to time-varying biases in the reanalysis fluxes as noticed in other studies. We conclude that even though its data record is short, GRACE provides new information that should be used to constrain future reanalyses toward a better representation of long-term water cycle evolution.

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A global assessment of accelerations in surface mass transport

Cited by 10 publications

References 21 publications

Recent Progress in Understanding and Projecting Regional and Global Mean Sea Level Change

Recent Progress in Understanding and Projecting Regional and Global Mean Sea Level Change

JTRF2014, the JPL Kalman filter and smoother realization of the International Terrestrial Reference System

Does GRACE see the terrestrial water cycle “intensifying”?

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