2024:
Svennevig et al. A rockslide-generated tsunami in a Greenland fjord rang Earth for 9 days. Science 385, 1196–1205 (2024) 13 September 2024. https://www.science.org/doi/10.1126/science.adm9247.
Abstract:
Climate change is increasingly predisposing polar regions to large landslides. Tsunamigenic landslides have occurred recently in Greenland (Kalaallit Nunaat), but none have been reported from the eastern fjords. In September 2023, we detected the start of a 9-day-long, global 10.88-millihertz (92-second) monochromatic very-long-period (VLP) seismic signal, originating from East Greenland. In this study, we demonstrate how this event started with a glacial thinning–induced rock-ice avalanche of 25 × 106 cubic meters plunging into Dickson Fjord, triggering a 200-meter-high tsunami. Simulations show that the tsunami stabilized into a 7-meter-high long-duration seiche with a frequency (11.45 millihertz) and slow amplitude decay that were nearly identical to the seismic signal. An oscillating, fjord-transverse single force with a maximum amplitude of 5 × 1011 newtons reproduced the seismic amplitudes and their radiation pattern relative to the fjord, demonstrating how a seiche directly caused the 9-day-long seismic signal. Our findings highlight how climate change is causing cascading, hazardous feedbacks between the cryosphere, hydrosphere, and lithosphere.
Christensen, T.R. Wetland emissions on the rise. Nat. Clim. Chang. (2024). https://doi.org/10.1038/s41558-024-01938-y.
Abstract:
Methane concentrations are rising faster than ever in the atmosphere. Now, a compilation of observations points towards increased methane emissions from Arctic wetlands as being partly responsible.
The rate of increase in atmospheric methane concentration has been accelerating since 2016, as shown by recent analyses of atmospheric records1. This calls for renewed attention to this strong greenhouse gas as a very important player in the global climate. The increase in atmospheric methane may be further considered a diagnosis of ‘illness’ in the Earth system, indicating a positive (amplifying) feedback to climate change. The sources of methane causing this acceleration are not yet clear. However, it is well known that substantial global wetland emissions of methane can contribute to it, and the tropical region is being pointed out as a potential source of this methane1,2. Writing in Nature Climate Change, Yuan et al.3 document a significant overarching increasing trend also in northern wetland emissions.
2023:
Dømgaard, M., Kjeldsen, K. K., Huiban, F., Carrivick, J. L., Khan, S. A., and Bjørk, A. A. (2023): Recent changes in drainage route and outburst magnitude of the Russell Glacier ice-dammed lake, West Greenland, The Cryosphere, 17, 1373–1387, https://doi.org/10.5194/tc-17-1373-2023, 2023.
Abstract: Glacial lake outburst floods (GLOFs) or jökulhlaups from ice-dammed lakes are frequent in Greenland and can influence local ice dynamics and bedrock motion, cause geomorphological changes, and pose flooding hazards. Multidecadal time series of lake drainage dates, volumes, and flood outlets are extremely rare. However, they are essential for determining the scale and frequency of future GLOFs, for identifying drainage mechanisms, and for mitigating downstream flood effects. In this study, we use high-resolution digital elevation models (DEMs) and orthophotos (0.1 × 0.1 m) generated from uncrewed-aerial-vehicle (UAV) field surveys, in combination with optical satellite imagery. This allows us to reconstruct robust lake volume changes associated with 14 GLOFs between 2007 and 2021 at Russell Glacier, West Greenland. As a result, this is one of the most comprehensive and longest records of ice-dammed lake drainages in Greenland to date. Importantly, we find a mean difference of ∼ 10 % between our lake drainage volumes when compared with estimates derived from a gauged hydrograph 27 km downstream. Due to thinning of the local ice dam, the potential maximum drainage volume in 2021 is ∼ 60 % smaller than that estimated to have drained in 2007. Our time series also reveals variations in the drainage dates ranging from late May to mid-September and drainage volumes ranging between 0.9 and 37.7 Mm3. We attribute these fluctuations between short periods of relatively high and low drainage volumes to a weakening of the ice dam and an incomplete sealing of the englacial tunnel following the large GLOFs. This syphoning drainage mechanism is triggered by a reduction in englacial meltwater, likely driven by late-season drainage and sudden air temperature reductions, as well as annual variations in the glacial drainage system. Furthermore, we provide geomorphological evidence of an additional drainage route first observed following the 2021 GLOF, with a subglacial or englacial flow pathway, as well as supraglacial water flow across the ice margin. It seems probable that the new drainage route will become dominant in the future. This will drive changes in the downstream geomorphology and raise the risk of flooding-related hazards as the existing buffering outlet lakes will be bypassed.
Box JE., Nielsen KP., Yang X., Niwano M., Wehrlé A., van As D., Fettweis X., Køltzow MAØ., Palmason B., Fausto RS., van den Broeke MR., Huai B., Ahlstrøm AP., Langley K., Dachauer A., Noël B. (2023). Greenland ice sheet rainfall climatology, extremes and atmospheric river rapids. Meteorol. Appl. 30:2134. https://doi.org/10.1002/met.2134
Abstract: Greenland rainfall has come into focus as a climate change indicator and from a variety of emerging cryospheric impacts. This study first evaluates rainfall in five state-of-the-art numerical prediction systems (NPSs) (CARRA, ERA5, NHM-SMAP, RACMO, MAR) using in situ rainfall data from two regions spanning from land onto the ice sheet. The new EU Copernicus Climate Change Service (C3S) Arctic Regional ReAnalysis (CARRA), with a relatively fine (2.5 km) horizontal grid spacing and extensive within-model-domain observational initialization, has the lowest average bias and highest explained variance relative to the field data. ERA5 inland wet bias versus CARRA is consistent with the field data and other research and is presumably due to more ERA5 topographic smoothing. A CARRA climatology 1991–2021 has rainfall increasing by more than one-third for the ice sheet and its peripheral ice masses. CARRA and in situ data illuminate extreme (above 300 mm per day) local rainfall episodes. A detailed examination CARRA data reveals the interplay of mass conservation that splits flow around southern Greenland and condensational buoyancy generation that maintains along-flow updraft ‘rapids’ 2 km above sea level, which produce rain bands within an atmospheric river interacting with Greenland. CARRA resolves gravity wave oscillations that initiate as a result of buoyancy offshore, which then amplify from terrain-forced uplift. In a detailed case study, CARRA resolves orographic intensification of rainfall by up to a factor of four, which is consistent with the field data.
2022:
Rysgaard S, Bjerge K, Boone W, Frandsen E, Graversen M, Høye TTi, Jensen B, Johnen G, Jackowicz-Korczynski MA, Kerby JT, Kortegaard S, Mastepanov M, Melvad C, Mikkelsen PS, Mortensen K, Nørgaard C, Poulsen E, Riis T, Sørensen LL, Christensen TR (2022). A mobile observatory powered by sun and wind for near real time measurements of atmospheric, glacial, terrestrial, limnic and coastal oceanic conditions in remote off-grid areas. 2468-0672 / 2022 Published by Elsevier Ltd. https://doi.org/10.1016/j.ohx.2022.e00331
Abstract: Climate change is rapidly altering the Arctic environment. Although long-term environmental observations have been made at a few locations in the Arctic, the incomplete coverage from ground stations is a main limitation to observations in these remote areas. Here we present a wind and sun powered multi-purpose mobile observatory (ARC-MO) that enables near real time measurements of air, ice, land, rivers, and marine parameters in remote off-grid areas. Two test units were constructed and placed in Northeast Greenland where they have collected data from cabled and wireless instruments deployed in the environment since late summer 2021. The two units can communicate locally via WiFi (units placed 25 km apart) and transmit near-real time data globally over satellite. Data are streamed live and accessible from (https://gios.org). The cost of one mobile observatory unit is c. 304.000€. These test units demonstrate the possibility for integrative and automated environmental data collection in remote coastal areas and could serve as models for a proposed global observatory system.
Box JE, Wehrlé A, van As, D, Fausto RS, Kjeldsen KK, Dachauer A, Ahlstrøm AP, and Picard G (2022). Greenland ice sheet rainfall, heat and albedo feedback impacts from the mid-August 2021 atmospheric River. Geophysical Research Letters, 49. https://doi.org/10.1029/2021GL097356
Abstract: Rainfall at the Greenland ice sheet Summit 14 August 2021, was delivered by an atmospheric river (AR). Extreme surface ablation expanded the all-Greenland bare ice area to near-record-high with snowline climbing up to 788 ± 90 m. Ice sheet wet snow extent reached 46%, a record high for the 15–31 August AMSR data since 2003. Heat-driven firn deflation averaged 0.14 ± 0.05 m at four accumulation area automatic weather stations (AWSs). Energy budget calculations from AWS data indicate that surface heating from rainfall is much smaller than from either the sensible, latent, net-longwave or solar energy fluxes. Sensitivity tests show that without the heat-driven snow-darkening, melt at 1,840 m would have totaled 28% less. Similarly, at 1,270 m elevation, without the bare ice exposure, melting would have been 51% less. Proglacial river discharge was the highest on record since 2006 for late August and confirms the melt-sustaining effect of the albedo feedback.
Video: Greenland Ice Sheet Atmospheric River – Rainfall, Heat and Albedo Feedback Impacts