The Transient Sensitivity of Sea Level Rise

As we warm our planet, oceans expand, ice on land melts, and sea levels rise. On century time scales, we find that the sea level response to warming can be characterized by a single metric: the transient sea level sensitivity. Historical sea level exhibits substantially higher sensitivity than model-based estimates of future climates in authoritative climate assessments. Implying recent projections could well underestimate the likely sea level rise by the end of this century.

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Grinsted, A. and Christensen, J. H., (2021) The transient sensitivity of sea level rise, Ocean Sci., 17, 181–186, doi:10.5194/os-17-181-2021 Share

Normalized US hurricane damage estimates using area of total destruction, 1900−2018

We present an approach to normalize hurricane damage, where damage is framed in terms of an equivalent area of total destruction. This has some advantages over customary normalization schemes, and we demonstrate that our record has reduced variance and correlates marginally better with wind speeds and pressure. That is, it allows us to better address climatic trends. We find that hurricanes are indeed becoming more damaging. The frequency of the very most damaging hurricanes has increased 3 times per century.

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Normalized US hurricane damage estimates using area of total destruction, 1900−2018, Aslak Grinsted, Peter Ditlevsen and Jens Hesselbjerg Christensen, Proceedings of the National Academy of Sciences. doi:10.1073/pnas.1912277116 Share

FEniCS on windows

FEniCS is a really nice tool for finite element modelling in python. It is difficult to install FEniCS on windows. The official instructions use a docker image. which I think is a bit heavy handed. I therefore installed it in a WSL-Ubuntu (Windows Subsystem for Linux). My experience with that has been friction free, so here are some very brief notes of what I did. In windows Enable WSL and install Ubuntu from the windows store Install VS Code In VS Code Install the WSL remote plug-in Install the “Python” plugin (the one from microsoft).

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On the limitations of using polarimetric radar sounding to infer the crystal-orientation fabric of ice masses

The orientation of ice-crystal grains in glacier ice locally co-evolve with and can enhance the flow of ice. Inferring the grain orientation structure inside glaciers and ice-sheets is therefore essential for improving the accuracy and realism of ice-flow models, with implications for reducing the uncertainty of future sea-level rise projections. In this work, we introduce a new radio-wave model and use it to investigate the extent to which radar surveys over glaciers and ice sheets can reveal the orientation information necessary to improve such ice-flow models. We show that conventional polarimetric radar surveys, where transmitted radio waves are typically incident perpendicular to the surface, might be poorly suited for the task; a configuration that is effectively blind to a specific but important component of the grain orientation structure. We find, however, that radio waves transmitted at an oblique angle to the surface might instead overcome this crucial limitation and allow the sought-after grain orientation information to be inferred.

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Rathmann, N., D. Lilien, A. Grinsted, T. Gerber, T.J. Young, D. Dahl-Jensen, On the limitations of using polarimetric radar sounding to infer the crystal-orientation fabric of ice masses, GRL, 2021. doi:10.1029/2021GL096244 Share

Ice thickness and volume of Renland Ice Cap, East Greenland

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Koldtoft, I., Grinsted, A., Vinther, B., & Hvidberg, C. (2021). Ice thickness and volume of the Renland Ice Cap, East Greenland. Journal of Glaciology, 1-13. doi:10.1017/jog.2021.11 Share

The anatomy of past abrupt warmings recorded in Greenland ice

It is not often that negative results gets published in a high impact journal. Here, we highlight the absence of a systematic pattern in the anatomy of abrupt changes as recorded in different ice parameters.

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Capron, E., Rasmussen, S.O., Popp, T.J. et al. The anatomy of past abrupt warmings recorded in Greenland ice. Nat Commun 12, 2106 (2021). https://doi.org/10.1038/s41467-021-22241-w Share

Effect of an orientation-dependent nonlinear grain fluidity on bulk directional enhancement-factors

Ice with a strong fabric deforms more readily in some directions. Nicholas Rathmann levels up the theory with a better treatment of how grains influence bulk properties. The impact can be an order of magnitude difference in bulk enhancement factors.

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Rathmann, N., Hvidberg, C., Grinsted, A., Lilien, D., & Dahl-Jensen, D. (2021). Effect of an orientation-dependent non-linear grain fluidity on bulk directional enhancement factors. Journal of Glaciology, 1-7. doi:10.1017/jog.2020.117 Share

Surface velocity of the Northeast Greenland Ice Stream (NEGIS)

The Northeast Greenland Ice Stream (NEGIS) extends around 600 km from its onset in the interior of Greenland to the coast. Several maps of surface velocity and topography in Greenland exist, but accuracy is limited due to the lack of validation data. Here we present results from a 5-year GPS survey in an interior section of NEGIS. We use the data to assess a list of satellite-derived ice velocity and surface elevation products and discuss the implications for the ice stream flow in the area.

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Hvidberg, C. S., Grinsted, A., Dahl-Jensen, D., Khan, S. A., Kusk, A., Andersen, J. K., Neckel, N., Solgaard, A., Karlsson, N. B., Kjær, H. A., and Vallelonga, P., Surface velocity of the Northeast Greenland Ice Stream (NEGIS), assessment of interior velocities derived from satellite data by GPS, The Cryosphere, 14, 3487–3502, doi:10.5194/tc-14-3487-2020, 2020. Share

Hagen Bræ, A Surging Glacier in North Greenland — 35 Years of Observations

Improved ice velocity measurements with Sentinel-1 TOPS interferometry.

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Solgaard, A. M., Simonsen, S. B., Grinsted, A., Mottram, R., Karlsson, N. B., Hansen, K., ... & Sørensen, L. S. (2020). Hagen Bræ A Surging Glacier in North Greenland—35 Years of Observations. Geophysical Research Letters, 47(6), e2019GL085802. Share

Improved ice velocity measurements with Sentinel-1 TOPS interferometry

Improved ice velocity measurements with Sentinel-1 TOPS interferometry.

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Andersen, J. K., Kusk, A., Boncori, J. P. M., Hvidberg, C. S., & Grinsted, A. (2020). Improved ice velocity measurements with Sentinel-1 TOPS interferometry. Remote Sensing, 12(12), 2014. Share

East Greenland ice core dust record reveals timing of Greenland ice sheet advance and retreat

Grains of dust in an ice core illustrate how fast a landscape is covered with ice after an ice age sets in.

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Simonsen, M.F., Baccolo, G., Blunier, T. et al. East Greenland ice core dust record reveals timing of Greenland ice sheet advance and retreat. Nat Commun 10, 4494 (2019). doi:10.1038/s41467-019-12546-2 Share

Sea-level change in the Dutch Wadden Sea

A thorough report on the sea-level change in the Dutch Wadden Sea.

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Vermeersen, B. L. A., Slangen, A. B. A., Gerkema, T., Baart, F., Cohen, K. M., Dangendorf, S., Duran-Matute, M., Frederikse, T., Grinsted, A., Hijma, M. P., Jevrejeva, S., Kiden, P., Kleinherenbrink, M., Meijles, E. W., Palmer, M. D., Rietbroek, R., Riva, R. E. M., Schulz, E., Slobbe, D. C., ... van der Wegen, M. (2018). Sea-level change in the Dutch Wadden Sea. Netherlands journal of geosciences-Geologie en mijnbouw, 97(3), 79-127. doi:10.1017/njg.2018.7 Share