Dynamics and history of northwestern Greenland Ice Sheet
Postdoctoral researcher, Stockholm University and Bolin Centre for Climate Research
2018 -
Combining ice sheet modelling with geological, oceanographic and climatic data to understand the dynamics and history of the northwestern part of the Greenland Ice Sheet.
2018 -
Combining ice sheet modelling with geological, oceanographic and climatic data to understand the dynamics and history of the northwestern part of the Greenland Ice Sheet.
Deglaciation of the Norwegian fjords
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PhD project 2014-2017
part of the Eurasian Ice Sheet and Climate Interactions (EISCLIM) project Åkesson, H. (2018). Deglaciation of the Norwegian fjords. PhD Thesis, University of Bergen. [Web] [PDF] [PhD defense press release (in Norwegian)] - defended: Jan 9, 2018 - opponents: Andreas Vieli (Univ. Zürich), Chris Stokes (Durham Univ.) -committee: Andreas Vieli (Univ. Zürich), Chris Stokes (Durham Univ.), Atle Nesje (Univ. Bergen) - advisors: Kerim H. Nisancioglu (Univ. Bergen), John Inge Svendsen (Univ. Bergen), Mathieu Morlighem (Univ. California, Irvine) Papers within thesis Paper I Åkesson, H., Nisancioglu, K. H., Giesen, R. H., and Morlighem, M.: Simulating the evolution of Hardangerjøkulen ice cap in southern Norway since the mid-Holocene and its sensitivity to climate change, The Cryosphere, 11, 281-302, doi:10.5194/tc-11-281-2017, 2017. [Web] [PDF] Paper II Åkesson H, Nisancioglu KH and Nick FM (2018) Impact of Fjord Geometry on Grounding Line Stability. Front. Earth Sci. 6:71. doi: 10.3389/feart.2018.00071. [Web] [PDF] Paper III Åkesson, H., Gyllencreutz, R., Mangerud, J., Svendsen, J.I., Nick, F.M., and Nisancioglu, K.H. Fast retreat of a marine outlet glacier in western Norway at the last glacial termination (in prep). [Full-text not available] Paper IV Steiger, N., Nisancioglu, K. H., Åkesson, H., de Fleurian, B., and Nick, F. M.: Simulated retreat of Jakobshavn Isbræ since the Little Ice Age controlled by geometry, The Cryosphere, 12, 2249-2266, https://doi.org/10.5194/tc-12-2249-2018, 2018. [Web] [PDF] Paper V. Åkesson, H., Morlighem, M., Nisancioglu, K. H., Svendsen, J. I., & Mangerud, J. (2018). Atmosphere-driven ice sheet mass loss paced by topography: Insights from modelling the south-western Scandinavian Ice Sheet. Quaternary Science Reviews, 195, 32-47. [Web] [PDF] In summary, my PhD thesis concerned the behaviour of fjord glaciers and small ice caps, both learning about those which drained the large ice sheet which covered northern Europe during the last deglaciation, and those of Greenland today. My focus is was on understanding the glaciological, topographic, climatic and oceanic controls on the retreat of these marine outlet glaciers. My tools were numerical ice flow models of varying complexity. Many of Greenland’s marine outlet glaciers have thinned, accelerated and retreated during the last two decades. Ocean warming is suggested to be one of the main drivers of the resulting mass loss. However, recent glacier changes involve considerable spatial and temporal variability. Similarly, reconstructions of marine outlet glaciers in Greenland and Norway indicate highly asynchronous retreat histories. I combine field data and modelling studies to assess to what extent marine outlet glaciers are controlled by ocean or atmosphere warming, as well as fjord geometry. I used this information to study how and why the Norwegian fjords became ice-free during the last deglaciation. A recent paper on the bed topography below the ice in Greenland revealed long, deep valleys extending much further inland than previously thought (Morlighem et al. 2014). Greenland will thus be affected by ocean warming and submarine melting much longer before marine outlet glaciers retreat up on land. The topography below the Greenland Ice Sheet resembles that of Norway, with high coastal mountains deeply incised by long valleys (fjords). Understanding deglaciation of fjords in Norway may thus provide important clues to what we can expect from the Greenland Ice Sheet in the future. The EISCLIM project (2014-2017) My PhD project was a part of the EISCLIM project, which focused on the style of growth and decay of the Eurasian ice sheet, and what forcings were responsible for these changes. EISCLIM comprised geological reconstructions and modelling of climate and ice dynamics on both the ice sheet wide and regional scales. Key partners in this project were Kerim H. Nisancioglu, John Inge Svendsen, Jan Mangerud, Anna Hughes, Kristian Vasskog, Jostein Bakke (all University of Bergen and Bjerknes Centre for Climate Research), Lev Tarasov (Memorial University of New Foundland), Nina Kirchner, Richard Gyllencreutz (both Stockholm University), Faezeh Nick (University centre in Svalbard), Jason Briner (State University of New York at Buffalo) and Brent Goehring (Purdue University). EISCLIM was funded by the Norwegian Research Council. References Morlighem, M., Rignot, E., Mouginot, J., Seroussi, H., & Larour, E. (2014). Deeply incised submarine glacial valleys beneath the Greenland ice sheet. Nature Geoscience. |
From Paper V: Åkesson et al. 2018. Modelled ice sheet geometry at (a) 15 ka, (b) 13 ka (Allerød), and (c) 12 ka, equivalent to the Younger Dryas maximum extent. For each time-slice, red solid and dotted lines represent maximum and minimum extent from geological reconstructions (Briner et al., 2014; Hughes et al., 2016; Gump et al., 2017; Mangerud et al., 2017).
From Paper II: Impact of fjord geometry on grounding line stability. Åkesson et al. 2018 Frontiers of Earth Science: Cryosphere
Figure 5. Modeled ice thickness at (a) 3800, (b) 2300, (c) 1900 and
1300 BP using our “best-fit” model parameters obtained from independent
calibration. Shown are also ice cap extent in AD1995
(black thick line) and corresponding drainage basins for outlet
glaciers Rembesdalskåka (SW) and Midtdalsbreen (NE; black thin
lines).
From Paper I: Åkesson et al. 2017, The Cryospphere
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Simulating the climatic response of Hardangerjøkulen ice cap in southern Norway since the Little Ice Age
Model mesh used to model Hardangerjøkulen ice cap. Colours indicate present-day ice thickness, the solid line represent present-day ice margin and the dashed line the flowline of the largest outlet glacier, Rembesdalskåka.
MSc Thesis 2013-2014
I was using a numerical ice flow model (the Ice Sheet System Model, ISSM; Larour et al. 2012) to understand the climatic response and dynamics of the Hardangerjøkulen ice cap (73 km2) in southern Norway during the last 300 years. I investigated the effeect of sliding parameterizations and the applicability of the Shallow Ice Approximation for small ice masses.
Using in incomplete description of ice flow, along with a simple implementation of mass balance, we were able to reproduce most of the observed and reconstructed glacier evolution from the Little Ice Age maximum in 1750 until today. We also found that the present-day Hardangerjøkulen ice cap is very sensitive to changes in mass balance. A shift in mass balance with only - 0.15 m water equivalents relative to the mean mass balance during the last 45 years will cause almost the entire ice cap to disappear.
This thesis was defended 11 June 2014 and graded A (scale A-F).
References
Larour, E., Seroussi, H., Morlighem, M., & Rignot, E. (2012). Continental scale, high order, high spatial resolution, ice sheet modeling using the Ice Sheet System Model (ISSM). Journal of Geophysical Research: Earth Surface (2003–2012), 117(F1).
Åkesson, H. (2014). Simulating the climatic response of Hardangerjøkulen in southern Norway since the Little Ice Age. MSc Thesis, University of Bergen. PDF
I was using a numerical ice flow model (the Ice Sheet System Model, ISSM; Larour et al. 2012) to understand the climatic response and dynamics of the Hardangerjøkulen ice cap (73 km2) in southern Norway during the last 300 years. I investigated the effeect of sliding parameterizations and the applicability of the Shallow Ice Approximation for small ice masses.
Using in incomplete description of ice flow, along with a simple implementation of mass balance, we were able to reproduce most of the observed and reconstructed glacier evolution from the Little Ice Age maximum in 1750 until today. We also found that the present-day Hardangerjøkulen ice cap is very sensitive to changes in mass balance. A shift in mass balance with only - 0.15 m water equivalents relative to the mean mass balance during the last 45 years will cause almost the entire ice cap to disappear.
This thesis was defended 11 June 2014 and graded A (scale A-F).
References
Larour, E., Seroussi, H., Morlighem, M., & Rignot, E. (2012). Continental scale, high order, high spatial resolution, ice sheet modeling using the Ice Sheet System Model (ISSM). Journal of Geophysical Research: Earth Surface (2003–2012), 117(F1).
Åkesson, H. (2014). Simulating the climatic response of Hardangerjøkulen in southern Norway since the Little Ice Age. MSc Thesis, University of Bergen. PDF