Háskóli Íslands

Like most glaciers and ice caps worldwide, Vatnajökull, the largest ice cap in Iceland, has been losing mass in the past few decades. It has lost about 135 km3 or ~4.5% of its volume in the period 1995-2019. In a new study from Institute of Earth Sciences, University of Iceland, published in the Journal of Glaciology (https://doi.org/10.1017/jog.2019.90), the future evolution of Vatnajökull is estimated by using a large range of available predictions from different climate models. The climate models were used to force an ice flow model and thus estimate the likely future dynamic changes of the ice cap. The energy balance model, which computes the energy components that control ablation of glaciers, is constrained with observations of mass balance and weather components (temperature, humidity, wind direction and strength, as well as incoming and outgoing short- and longwave radiation) at the surface of the glacier that have been collected on Vatnajökull during the last 25 years.

We investigated the changes under a moderate CO2 emission scenario leading to an average temperature increase of ~2.4°C by 2100, and a high (business-as-usual) emission scenario with an average temperature increase of ~3.5°C by 2100. Both scenarios are provided by the Intergovernmental Panel on Climate Change (IPCC). After 2100, we assume that the climate has become stable and we continue the simulations for another 200 years by repeating the climate from 2081-2100. Because it takes Vatnajökull a few decades to adjust to a new climate the mass loss for both climate scenarios is estimated to be 15-30% of its volume until 2100.

Under the moderate warming scenario, 30-65% of the volume of Vatnajökull is projected to disappear by 2300, but 50-95% according to the extreme warming scenario. The large span in the projected changes is due to the use of different climate model projections, which have large differences in e.g. temperature and precipitation changes, even when using the same greenhouse gas concentration. As many studies before, this study shows that it is important to consider a range of projections when estimating future changes.

The model simulations neglect some feedback mechanisms between the ice flow model and the climate forcing. We estimate that if this effect is included, about 10-20% more of the volume will likely disappear by 2300.

Data used in this project have been collected with support from European Research Council, The Icelandic Center for Research (Rannís), National Power Company of Iceland and Iceland Road Authority. The project SAMAR is supported by Rannís (ID 140920-051) and doctoral grant from the research fund of University of Iceland. The projected future climate is from CORDEX (www.cordex.org)

Louise Steffensen Schmidt and Sveinbjörn Steinþórsson assemblin Automatic Weather Station in spring 2015

Photo at top: Automatic Weather Stations measures wind, temperature, humidity, short-wave radiation and lowering of the surface to estimate energy balance components at the surface of a glacier.

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