Resolving sea level contributions by identifying fingerprints in time-variable gravity and altimetry

Rietbroek, Roelof; Brunnabend, Sandra-Esther; Kusche, Jürgen; Schröter, Jens

doi:10.1016/j.jog.2011.06.007

Cited by 46 publications

(53 citation statements)

References 37 publications

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“…In our forward modeling-least-squares approach (41,42), the different contributions are parameterized by predefined spatial patterns, each scaled with an unknown time-varying magnitude. The spatial information for each pattern, coined "fingerprints," originates from a priori data, whereas the time evolution is estimated from altimetry and GRACE data.…”

Section: Methodsmentioning

confidence: 99%

“…This involves solving the so-called "Sea-Level Equation" (44), which, in our case, is performed in the spherical harmonic domain (41,45). In addition, contributions from five separate GIA patterns, each representing the effect of a former glacial mass (Laurentide, Antarctica, Greenland, Fennoscandia, and auxiliary glacial masses), are used as fingerprints.…”

Section: Methodsmentioning

confidence: 99%

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Revisiting the contemporary sea-level budget on global and regional scales

Rietbroek

Brunnabend

Kusche

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

203

211

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Dividing the sea-level budget into contributions from ice sheets and glaciers, the water cycle, steric expansion, and crustal movement is challenging, especially on regional scales. Here, Gravity Recovery And Climate Experiment (GRACE) gravity observations and sea-level anomalies from altimetry are used in a joint inversion, ensuring a consistent decomposition of the global and regional sea-level rise budget. Over the years 2002-2014, we find a global mean steric trend of 1.38 ± 0.16 mm/y, compared with a total trend of 2.74 ± 0.58 mm/y. This is significantly larger than steric trends derived from in situ temperature/salinity profiles and models which range from 0.66 ± 0.2 to 0.94 ± 0.1 mm/y. Mass contributions from ice sheets and glaciers (1.37 ± 0.09 mm/y, accelerating with 0.03 ± 0.02 mm/y 2 ) are offset by a negative hydrological component (−0.29 ± 0.26 mm/y). The combined mass rate (1.08 ± 0.3 mm/y) is smaller than previous GRACE estimates (up to 2 mm/y), but it is consistent with the sum of individual contributions (ice sheets, glaciers, and hydrology) found in literature. The altimetric sea-level budget is closed by coestimating a remaining component of 0.22 ± 0.26 mm/y. Well above average sea-level rise is found regionally near the Philippines (14.7 ± 4.39 mm/y) and Indonesia (8.3 ± 4.7 mm/y) which is dominated by steric components (11.2 ± 3.58 mm/y and 6.4 ± 3.18 mm/y, respectively). In contrast, in the central and Eastern part of the Pacific, negative steric trends (down to −2.8 ± 1.53 mm/y) are detected. Significant regional components are found, up to 5.3 ± 2.6 mm/y in the northwest Atlantic, which are likely due to ocean bottom pressure variations.lobal sea-level rise has been identified as one of the major threats associated with global climate change (1, 2). However, from the perspective of assessment-and decision-making, regional estimates of sea-level rise are even more important to formulate meaningful adaptation plans on a national or international level. Besides the magnitude of the total sea-level rise itself, identifying dominant drivers, and their corresponding uncertainties, may also prove beneficial for projection studies.Historical records from tide gauges indicate a sea-level rate of about 1.7 mm/y over the period 1900-2009, where it must be noted that tide gauges indicate an acceleration (0.009-0.017 mm/y 2 ) over the last century (3-5). Besides the steric expansion of sea water due to temperature changes, the ongoing melting and ablation of ice sheets in Greenland and Antarctica and other land glaciers cause the sea level to rise. Hydrological mass variability on land and reservoir construction have been found to cause a negative trend (6-9). Furthermore, meltwater, precipitation, or evaporation result in regional salinity changes, leaving steric signatures in sea level once the barotropic component has been compensated (10). For an observer at the coast, crustal movement, caused by glacial isostatic adjustment (GIA), tectonics, or local subsidence may also significantly affect the r...

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Revisiting the contemporary sea-level budget on global and regional scales

Rietbroek

Brunnabend

Kusche

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

203

211

View full text Add to dashboard Cite

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“…Eleven contributions are derived from monthly spherical-harmonic solutions of the global gravity field using different approaches 55,56,[61][62][63][64][65][66] , which can be loosely classified as (i) region-integration approaches 55,65,66 , (ii) post-spherical-harmonic mascon approaches 56,[61][62][63] , (iii) forward-modelling approaches 62,64 , which essentially involve modelling of mass change with iterative comparison to the GRACE-derived signal, and (iv) approaches that use Slepian functions 67 . One final estimate 68 made use of satellite altimetry data; although this estimate was excluded from our gravity ensemble average because it is a hybrid solution, it is presented alongside the gravimetry-only results for comparison. No restrictions were imposed on the choice of GIA correction; among the GRACE solutions we consider six different models 21,24,26,30,31,43 .…”

Section: −1mentioning

confidence: 99%

Mass balance of the Antarctic Ice Sheet from 1992 to 2017

2018

Nature

829

476

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The iMBiE team* The Antarctic Ice Sheet is an important indicator of climate change and driver of sea-level rise. Here we combine satellite observations of its changing volume, flow and gravitational attraction with modelling of its surface mass balance to show that it lost 2,720 ± 1,390 billion tonnes of ice between 1992 and 2017, which corresponds to an increase in mean sea level of 7.6 ± 3.9 millimetres (errors are one standard deviation). Over this period, ocean-driven melting has caused rates of ice loss from West Antarctica to increase from 53 ± 29 billion to 159 ± 26 billion tonnes per year; ice-shelf collapse has increased the rate of ice loss from the Antarctic Peninsula from 7 ± 13 billion to 33 ± 16 billion tonnes per year. We find large variations in and among model estimates of surface mass balance and glacial isostatic adjustment for East Antarctica, with its average rate of mass gain over the period 1992-2017 (5 ± 46 billion tonnes per year) being the least certain.

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“…The first line (SW) reports the trend computed for Swenson et al (2008). The second line (RR) reports the trend found in Rietbroek et al (2012b). The third and fourth lines use the trend computed using the SLR time series (X = −0.131, Y = 0.352, Z = −0.637) minus the GIA geocenter motion given in Wu et al (2012) dences, and we use them together with the Riva et al (2009) empirical GIA model.…”

Section: Glacial Isostatic Adjustmentmentioning

confidence: 99%

Scatter of mass changes estimates at basin scale for Greenland and Antarctica

Barletta¹,

Sørensen²,

Forsberg³

2013

The Cryosphere

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Abstract. During the last decade, the GRACE mission has provided valuable data for determining the mass changes of the Greenland and Antarctic ice sheets. Yet, discrepancies still exist in the published mass balance results, and comprehensive analyses on the sources of errors and discrepancies are lacking. Here, we present monthly mass changes together with trends derived from GRACE data at basin scale for both the Greenland and Antarctic ice sheets, and we assess the variability and errors for each of the possible sources of discrepancies, and we do this in an unprecedented systematic way, taking into account mass inference methods, data sets and background models. We find a very good agreement between the monthly mass change results derived from two independent methods, which represents a cross validation. For the monthly solutions, we find that most of the scatter is caused by the use of the two different data sets rather than the two different methods applied. Besides the well-known GIA trend uncertainty, we find that the geocenter motion and the recent de-aliasing corrections significantly impact the trends, with contributions of +13.2 Gt yr −1 and −20 Gt yr −1 , respectively, for Antarctica, which is more affected by these than Greenland. We show differences between the use of release RL04 and the new RL05 and confirm a lower noise content in the new release. The overall scatter of the solutions well exceeds the uncertainties propagated from the data errors and the leakage (as done in the past); hence we calculate new sound total errors for the monthly solutions and the trends.We find that the scatter in the monthly solutions caused by applying different estimates of geocenter motion time series (degree-1 corrections) is significant -contributing with up to 40% of the total error.For the whole GRACE period (2003-2011) our trend estimate for Greenland is −234 ±20 Gt yr −1 and −83 ± 36 Gt yr −1 for Antarctica (−111 ± 15 Gt yr −1 in the western part). We also find a clear (with respect to our errors) increase of mass loss in the last four years.

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Resolving sea level contributions by identifying fingerprints in time-variable gravity and altimetry

Cited by 46 publications

References 37 publications

Revisiting the contemporary sea-level budget on global and regional scales

Revisiting the contemporary sea-level budget on global and regional scales

Mass balance of the Antarctic Ice Sheet from 1992 to 2017

Scatter of mass changes estimates at basin scale for Greenland and Antarctica

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