Abstract
In recent decades, Greenland’s has been losing an increasing amount of ice mass, contributing to global sea level rise and changes in thermohaline ocean circulation. Half of Greenland’s mass loss arises from widespread glacier speed-up and thinning as a reaction to changes in air and ocean temperatures. Although the relation between increased mass los , glacier retreat and changing climate is evident, the underlying processes are not entirely understood yet and it remains challenging for ice flow models to reproduce the dynamic changes. Hence, we need to reduce the simulation uncertainties in order to improve global sea level rise predictions and perceive its impact to our lives.
This thesis focuses on simulating marine-terminating glacier front changes with a numerical ice flow model and evaluates simulated glacier thinning and acceleration given observations. In addition, statistical regression analysis investigates the impact of surface air temperatures on glacier retreat in 1999–2015.
Prescribing the simulated glacier front evolution to match observations on Upernavik Isstrøm (UI) during 1849–2012 results in recently observed surface elevation lowering and speed-up of the three major UI outlet glaciers. The change in mass flux resulting from the prescribed glacier retreat contributes to 70% of UI’s mass change over the simulation periods. The residual mass change is due to surface mass balance. A second simulation on the fastest UI glacier (UI-1) reveals that frontal melt rates of maximum 3–3.5md􀀀1 are sufficient to match observed glacier-front dynamics between 1985 and 2017. The simulation adapts the theory of mixing ocean circulation and meltwater runoff triggering stress-driven glacier retreat. A third study confirms, that surface air temperature changes can predict glacier retreat to a certain degree and foremost define the variation of retreat rates.
The thesis implies the importance of incorporating glacier-front dynamics into ice sheet models in order to match observations and verifies atmospheric and oceanic forcing as important triggers for glacier retreat. Moreover, it is essential to incorporate observations into simulations to evaluate and better understand the ongoing glacial processes during glacier retreat.
This thesis focuses on simulating marine-terminating glacier front changes with a numerical ice flow model and evaluates simulated glacier thinning and acceleration given observations. In addition, statistical regression analysis investigates the impact of surface air temperatures on glacier retreat in 1999–2015.
Prescribing the simulated glacier front evolution to match observations on Upernavik Isstrøm (UI) during 1849–2012 results in recently observed surface elevation lowering and speed-up of the three major UI outlet glaciers. The change in mass flux resulting from the prescribed glacier retreat contributes to 70% of UI’s mass change over the simulation periods. The residual mass change is due to surface mass balance. A second simulation on the fastest UI glacier (UI-1) reveals that frontal melt rates of maximum 3–3.5md􀀀1 are sufficient to match observed glacier-front dynamics between 1985 and 2017. The simulation adapts the theory of mixing ocean circulation and meltwater runoff triggering stress-driven glacier retreat. A third study confirms, that surface air temperature changes can predict glacier retreat to a certain degree and foremost define the variation of retreat rates.
The thesis implies the importance of incorporating glacier-front dynamics into ice sheet models in order to match observations and verifies atmospheric and oceanic forcing as important triggers for glacier retreat. Moreover, it is essential to incorporate observations into simulations to evaluate and better understand the ongoing glacial processes during glacier retreat.
| Originalsprog | Engelsk |
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| Forlag | Natural History Museum of Denmark, Faculty of Science, University of Copenhagen |
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| Status | Udgivet - 2018 |
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