ALPS: A Unified Framework for Modeling Time Series of Land Ice Changes

Shekhar, Prashant; Csathó, Beáta; Schenk, Tony; Roberts, C.; Patra, Abani

doi:10.1109/tgrs.2020.3027190

Cited by 7 publications

(8 citation statements)

References 53 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…5; Csatho and others, 2014; Khan and others, 2022). Temporal variations in this altimetry-observed thickening trend can be explained by recent surface mass balance variability (Shekhar and others, 2021). Over longer timescales, shifting spatial gradients in net snow accumulation can influence divide position and ice-sheet form and flow (van der Veen, 2001).…”

Section: Thickness Trendsmentioning

confidence: 81%

Sixty years of ice form and flow at Camp Century, Greenland

et al. 2022

Self Cite

View full text Add to dashboard Cite

The magnitude and azimuth of horizontal ice flow at Camp Century, Greenland have been measured several times since 1963. Here, we provide a further two independent measurements over the 2017–21 period. Our consensus estimate of horizontal ice flow from four independent satellite-positioning solutions is 3.65 ± 0.13 m a−1 at an azimuth of 236 ± 2°. A portion of the small, but significant, differences in ice velocity and azimuth reported between studies likely results from spatial gradients in ice flow. This highlights the importance of restricting inter-study comparisons of ice flow estimates to measurements surveyed within a horizontal distance of one ice thickness from each other. We suggest that ice flow at Camp Century is stable on seasonal to multi-decadal timescales. The airborne and satellite laser altimetry record indicates an ice thickening trend of 1.1 ± 0.3 cm a−1 since 1994. This thickening trend is qualitatively consistent with previously inferred ongoing millennial-scale ice thickening at Camp Century. The ice flow divide immediately north of Camp Century may now be migrating southward, although the reasons for this divide migration are poorly understood. The Camp Century flowlines presently terminate in the vicinity of Innaqqissorsuup Oqquani Sermeq (Gade Gletsjer) on the Melville Bay coast.

show abstract

Section: Thickness Trendsmentioning

confidence: 81%

Sixty years of ice form and flow at Camp Century, Greenland

et al. 2022

Self Cite

View full text Add to dashboard Cite

show abstract

“…This quantity is a useful measure of how out of balance the ice dynamics are with the climate and, thus, it is a good metric for evaluating the ensemble. Ice sheet surface elevation change time series are obtained from airborne and spaceborne laser altimetry using the Surface Elevation Reconstruction and Change (SERAC) method (Schenk and Csatho, 2012;Shekhar et al, 2020). To obtain dynamic surface elevation change, we account for thickness change anomalies due to surface and firn processes by applying the Institute for Marine and Atmospheric research Utrech (IMAU) Firn Densification Model (FDM), which simulates thickness change of the firn, forced by RACMO2.3p2 (Ligtenberg et al, 2018).…”

Section: Dynamic Thickness Changementioning

confidence: 99%

“…We then fit a continuous function to the discrete SERAC estimates through time. Time series with a magnitude of dynamic thickness change greater than 5 m over the entire SERAC time series are typically characterized by complex temporal behavior; at these locations, we use the Approximation by Localized Penalized Spline (ALPS) method (Shekhar et al, 2020) to approximate a continuous function through time. Time series with a magnitude of dynamic thickness change less than 5 m over the entire SERAC time series exhibit less complex behavior and we fit a cubic polynomial to the discrete SERAC estimates at these locations.…”

Section: Dynamic Thickness Changementioning

confidence: 99%

Choice of observation type affects Bayesian calibration of ice sheet model projections

Felikson

Nowicki

Nias

et al. 2022

Preprint

View full text Add to dashboard Cite

Abstract. Determining reliable probability distributions for ice sheet mass change over the coming century is critical to improving uncertainties in sea-level rise projections. Bayesian calibration, a method for constraining projection uncertainty using observations, has been previously applied to ice sheet projections but the impact of the chosen observation type on the calibrated posterior probability distributions has not been quantified. Here, we perform three separate Bayesian calibrations to constrain uncertainty in Greenland Ice Sheet projections using observations of velocity change, dynamic thickness change, and mass change. Comparing the posterior probability distributions shows that the maximum a posteriori ice sheet mass change can differ by 130 % for the particular model ensemble that we used, depending on the observation type used in the calibration. More importantly for risk-averse sea level planning, posterior probabilities of high-end mass change scenarios are highly sensitive to the observation selected for calibration. Finally, we show that using mass change observations alone may result in projections that overestimate flow acceleration and underestimate dynamic thinning around the margin of the ice sheet.

show abstract

“…Finally, elevation change time series will be combined with models enabling estimation of mass change time series. 70,71 By deriving time series of elevation and mass changes with error estimates to decadal changes of an entire ice sheet, the resulting tool will provide much-needed flexibility for intercomparisons, both between observations and between models and observations.…”

Section: Surface Elevation Reconstruction and Change Detectionmentioning

confidence: 99%

“…Tools to interpolate the irregularly distributed observations into user‐defined meshes or grids, to estimate ice elevation and thickness change, and to perform spatial interpolation will be incorporated into the workflow. Finally, elevation change time series will be combined with models enabling estimation of mass change time series 70,71 . By deriving time series of elevation and mass changes with error estimates to decadal changes of an entire ice sheet, the resulting tool will provide much‐needed flexibility for intercomparisons, both between observations and between models and observations.…”

Section: Community Codesmentioning

confidence: 99%

GHub: Building a glaciology gateway to unify a community

Sperhac

Poinar

Jones-Ivey

et al. 2020

Concurrency and Computation

Self Cite

View full text Add to dashboard Cite

There is no consensus on how quickly the earth's ice sheets are melting due to global warming, nor on the ramifications to sea level rise. Due to its potential effects on coastal populations and global economies, sea level rise is a grave concern, making ice melt rates an important area of study. The ice-sheet science community consists of two groups that perform related but distinct kinds of research: a data community, and a model building community. The data community characterizes past and current states of the ice sheets by assembling data from field and satellite observations. The modeling community forecasts the rate of ice-sheet decline with computational models validated against observations. Although observational data and models depend on one another, these two groups are not well integrated. Better coordination between data collection efforts and modeling efforts is imperative if we are to improve our understanding of ice sheet loss rates. We present a new science gateway, GHub, a collaboration space for ice sheet scientists. This web-accessible gateway will host datasets and modeling workflows, and provide access to codes that enable tool building by the ice sheet science community. Using GHub, we will collect and centralize existing datasets, creating data products that more completely catalog the ice sheets of Greenland and Antarctica. We will build workflows for model validation and uncertainty quantification, extending existing ice sheet models. Finally, we will host existing community codes, enabling scientists to build new tools utilizing them. With this new cyberinfrastructure, ice sheet scientists will gain integrated tools to quantify the rate and extent of sea level rise, benefitting human societies around the globe.

show abstract

ALPS: A Unified Framework for Modeling Time Series of Land Ice Changes

Cited by 7 publications

References 53 publications

Sixty years of ice form and flow at Camp Century, Greenland

Sixty years of ice form and flow at Camp Century, Greenland

Choice of observation type affects Bayesian calibration of ice sheet model projections

GHub: Building a glaciology gateway to unify a community

Contact Info

Product

Resources

About