Greenland Ice Sheet Mass Balance (1992–2020) From Calibrated Radar Altimetry

Simonsen, Sebastian B.; Barletta, V; Colgan, William; Sørensen, Louise Sandberg

doi:10.1029/2020gl091216

Cited by 28 publications

(50 citation statements)

References 46 publications

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“…Satellite-radar altimetry data are key in documenting the most recent changes in Earth's cryosphere [1][2][3][4][5][6][7][8][9]. Due to the radars' large beam-limited footprint (∼13 km in diameter), conventional radar altimetry has difficulties in mapping regions with highly varying surface relief.…”

Section: Introductionmentioning

confidence: 99%

Regional Assessments of Surface Ice Elevations from Swath-Processed CryoSat-2 SARIn Data

et al. 2021

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The Arctic responds rapidly to climate change, and the melting of land ice is a major contributor to the observed present-day sea-level rise. The coastal regions of these ice-covered areas are showing the most dramatic changes in the form of widespread thinning. Therefore, it is vital to improve the monitoring of these areas to help us better understand their contribution to present-day sea levels. In this study, we derive ice-surface elevations from the swath processing of CryoSat-2 SARIn data, and evaluate the results in several Arctic regions. In contrast to the conventional retracking of radar data, swath processing greatly enhances spatial coverage as it uses the majority of information in the radar waveform to create a swath of elevation measurements. However, detailed validation procedures for swath-processed data are important to assess the performance of the method. Therefore, a range of validation activities were carried out to evaluate the performance of the swath processor in four different regions in the Arctic. We assessed accuracy by investigating both intramission crossover elevation differences, and comparisons to independent elevation data. The validation data consisted of both air- and spaceborne laser altimetry, and airborne X-band radar data. There were varying elevation biases between CryoSat-2 and the validation datasets. The best agreement was found for CryoSat-2 and ICESat-2 over the Helheim region in June 2019. To test the stability of the swath processor, we applied two different coherence thresholds. The number of data points was increased by approximately 25% when decreasing the coherence threshold in the processor from 0.8 to 0.6. However, depending on the region, this came with the cost of an increase of 33–65% in standard deviation of the intramission differences. Our study highlights the importance of selecting an appropriate coherence threshold for the swath processor. Coherence threshold should be chosen on a case-specific basis depending on the need for enhanced spatial coverage or accuracy.

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Section: Introductionmentioning

confidence: 99%

Regional Assessments of Surface Ice Elevations from Swath-Processed CryoSat-2 SARIn Data

et al. 2021

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“…Although This Study has a small (−11 Gt yr −1 ) bias in comparison to Simonsen et al (2021a) VC, there is a relatively high RMSE of 86 Gt yr −1 and a mid-range correlation (r 2 = 0.62). This suggests that while both This Study and VC agree on the total mass loss of the ice sheet, they disagree on the precise temporal distribution of this mass loss.…”

Section: Vcmentioning

confidence: 63%

“…6). These products are the most recent IO product (Mouginot et al, 2019), the previous PROMICE mass balance product (Colgan et al, 2019;data: Colgan, 2021), the two mostly independent methods of estimating ice sheet mass change, GMB (Barletta et al, 2013;data: Barletta et al, 2020) and VC (Simonsen et al, 2021a;data: Simonsen et al, 2021b), and the IMBIE2 data (IMBIE Team, 2019). In addition to this, we evaluate the reconstructed Kjeldsen et al (2015) (data: Box et al, 2021) and This Study data during the overlapping period 1986 through 2012.…”

Section: Products Used For Validationmentioning

confidence: 99%

“…There are three common methods for estimating mass balance -changes in gravity (Barletta et al, 2013;Groh et al, 2019;IMBIE Team, 2019;Velicogna et al, 2020), changes in volume (Simonsen et al, 2021a;Sørensen et al, 2011; Figure 1. Annual mass balance (black lines), surface mass balance (blue lines), and discharge plus basal mass balance (dashed grey) in Gt yr −1 for each of the seven Mouginot and Rignot (2019) regions.…”

Section: Introductionmentioning

confidence: 99%

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Greenland ice sheet mass balance from 1840 through next week

Mankoff

Fettweis

Langen

et al. 2021

Earth Syst. Sci. Data

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Abstract. The mass of the Greenland ice sheet is declining as mass gain from snow accumulation is exceeded by mass loss from surface meltwater runoff, marine-terminating glacier calving and submarine melting, and basal melting. Here we use the input–output (IO) method to estimate mass change from 1840 through next week. Surface mass balance (SMB) gains and losses come from a semi-empirical SMB model from 1840 through 1985 and three regional climate models (RCMs; HIRHAM/HARMONIE, Modèle Atmosphérique Régional – MAR, and RACMO – Regional Atmospheric Climate MOdel) from 1986 through next week. Additional non-SMB losses come from a marine-terminating glacier ice discharge product and a basal mass balance model. From these products we provide an annual estimate of Greenland ice sheet mass balance from 1840 through 1985 and a daily estimate at sector and region scale from 1986 through next week. This product updates daily and is the first IO product to include the basal mass balance which is a source of an additional ∼24 Gt yr−1 of mass loss. Our results demonstrate an accelerating ice-sheet-scale mass loss and general agreement (coefficient of determination, r2, ranges from 0.62 to 0.94) among six other products, including gravitational, volume, and other IO mass balance estimates. Results from this study are available at https://doi.org/10.22008/FK2/OHI23Z (Mankoff et al., 2021).

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“…Fram Strait sea ice export is the largest dynamic sink of the Arctic freshwater cycle. The increase in Fram Strait sea ice export detected from long-term monitoring of sea ice area has been suspected as the cause of Arctic sea ice volume loss, in particular for the multiyear thick sea ice within the Arctic Ocean (Smedsrud et al, 2017;Ricker et al, 2018). Using the more recent sea ice thickness retrievals, Spreen et al (2020) actually showed that in volume, the Fram Strait export has in fact been decreasing at 27 % per decade over 1992-2014, on par with the Fram Strait and Arctic ice thickness.…”

Section: Sea Icementioning

confidence: 99%

Freshwater in the Arctic Ocean 2010–2019

Solomon

Heuzé²,

Rabe

et al. 2021

Ocean Sci.

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Abstract. The Arctic climate system is rapidly transitioning into a new regime with a reduction in the extent of sea ice, enhanced mixing in the ocean and atmosphere, and thus enhanced coupling within the ocean–ice–atmosphere system; these physical changes are leading to ecosystem changes in the Arctic Ocean. In this review paper, we assess one of the critically important aspects of this new regime, the variability of Arctic freshwater, which plays a fundamental role in the Arctic climate system by impacting ocean stratification and sea ice formation or melt. Liquid and solid freshwater exports also affect the global climate system, notably by impacting the global ocean overturning circulation. We assess how freshwater budgets have changed relative to the 2000–2010 period. We include discussions of processes such as poleward atmospheric moisture transport, runoff from the Greenland Ice Sheet and Arctic glaciers, the role of snow on sea ice, and vertical redistribution. Notably, sea ice cover has become more seasonal and more mobile; the mass loss of the Greenland Ice Sheet increased in the 2010s (particularly in the western, northern, and southern regions) and imported warm, salty Atlantic waters have shoaled. During 2000–2010, the Arctic Oscillation and moisture transport into the Arctic are in-phase and have a positive trend. This cyclonic atmospheric circulation pattern forces reduced freshwater content on the Atlantic–Eurasian side of the Arctic Ocean and freshwater gains in the Beaufort Gyre. We show that the trend in Arctic freshwater content in the 2010s has stabilized relative to the 2000s, potentially due to an increased compensation between a freshening of the Beaufort Gyre and a reduction in freshwater in the rest of the Arctic Ocean. However, large inter-model spread across the ocean reanalyses and uncertainty in the observations used in this study prevent a definitive conclusion about the degree of this compensation.

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Greenland Ice Sheet Mass Balance (1992–2020) From Calibrated Radar Altimetry

Cited by 28 publications

References 46 publications

Regional Assessments of Surface Ice Elevations from Swath-Processed CryoSat-2 SARIn Data

Regional Assessments of Surface Ice Elevations from Swath-Processed CryoSat-2 SARIn Data

Greenland ice sheet mass balance from 1840 through next week

Freshwater in the Arctic Ocean 2010–2019

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