Institute for Marine and Atmospheric Research Utrecht

Utrecht, Netherlands

Institute for Marine and Atmospheric Research Utrecht

Utrecht, Netherlands
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News Article | May 10, 2017

In a corner of the Swiss Alps, a snow machine pointed at a patch of ice is testing a new theory: Could manufactured snow help stop the retreat of a glacier? Since 1860, the Morteratsch glacier in Switzerland has shrunk back 2.5 kilometers, or more than half the length of Central Park. Each year it’s losing another 115 feet of ice. Other glaciers are also shrinking quickly–but because Morteratsch draws crowds, the local community decided to reach out to researchers to try to find a way to preserve it. “This particular glacier is a very big tourist attraction,” says Johannes Oerlemans, a glaciologist from the Institute for Marine and Atmospheric Research Utrecht in the Netherlands who was one of the researchers the community approached for help. “It’s one of the few that is very easy to reach. We always say it’s the single glacier in the Alps that you can reach by wheelchair.” Now the glacier has retreated so much that it’s barely visible from the most accessible viewpoint at the end of a road. For the last decade, a nearby ski slope has used one form of protection–a giant white fleece blanket that covers the ice each summer to slow melting–on a glacier called Dizvolezzafirn that underlies a ski run. The project works. Instead of shrinking, the glacier has thickened by about 10 meters over 10 years. Locals wondered if something similar could be done for the larger glacier. “We think that’s impossible,” Oerlemans says. “It’s 100 times bigger. You cannot cover a glacier of that size with fleece. But then we looked at other options, and we thought that perhaps something can be done by trying to keep part of the melt zone white in summer.” A cover of snow would reflect away sunlight, and insulate the ice. “If you do this in an area that’s large enough, you may at least be able to slow down the retreat of the glacier.” In models, Oerlemans and other researchers found that it should be possible to maintain a cover of snow on the glacier through the summer by making artificial snow from local meltwater. Using standard snow machines wouldn’t be practical–the project would require thousands of them–but the researchers think that a different kind of technology might work. While the technology has yet to be designed, the basic idea is to attach a snow machine to an aerial tramway that is suspended between mountain peaks, so that it could move back and forth to cover a large surface with snow. “It’s not without problems, but I think in the long run it has a better chance that you can cover a large area,” he says. If it works, and if funding is feasible, the approach could potentially be used in other parts of the world, such as Peru, where glaciers provide a critical source of drinking water.

de Vries H.,Royal Netherlands Meteorological Institute | van de Wal R.S.W.,Institute for Marine and Atmospheric Research Utrecht
Climatic Change | Year: 2016

In a commentary paper, Bamber et al. (Nat Clim Change 3:424–427, 2016) respond to our recent assessment (De Vries and Van de Wal Clim Change 1–14, 2015) of their expert judgment based study on projections of future sea level rise due to the melting of the large ice sheets (Bamber and Aspinall Nat Clim Chang 3:424–427, 2013). In this response we comment on their remarks. © 2016, Springer Science+Business Media Dordrecht.

Holzinger R.,Institute for Marine and Atmospheric Research Utrecht | Kasper-Giebl A.,Vienna University of Technology | Staudinger M.,Cent Institute Meteorol And Geodynam | Schauer G.,Cent Institute Meteorol And Geodynam | Rockmann T.,Institute for Marine and Atmospheric Research Utrecht
Atmospheric Chemistry and Physics | Year: 2010

For the first time a high mass resolution thermal desorption proton transfer reaction mass spectrometer (hr-TD-PTR-MS) was deployed in the field to analyze the composition of the organic fraction of aerosols. We report on measurements from the remote Mt. Sonnblick observatory in the Austrian alps (3108 m a.s.l.) during a 7 week period in summer 2009. A total of 638 mass peaks in the range 18-392 Da were detected and quantified in aerosols. An empirical formula was tentatively attributed to 464 of these compounds by custom-made data analysis routines which consider compounds containing C, H, O, N, and S atoms. Most of the other (unidentified) compounds must contain other elements – most likely halogenated compounds. The mean total concentration of all detected compounds was 1.1 μg mg-3. Oxygenated hydrocarbons constitute the bulk of the aerosol mass (75%) followed by organic nitrogen compounds (9%), inorganic compounds (mostly NH3, 8%), unidentified/halogenated (3.8%), hydrocarbons (2.7%), and organic sulfur compounds (0.8%). The measured O/C ratios are lower than expected and suggest a significant effect from charring. Organic carbon concentrations measured with TD-PTR-MS were about 25% lower than measurements on high volume filter samples. © 2010 Author(s).

de Vries H.,Royal Netherlands Meteorological Institute | van de Wal R.S.W.,Institute for Marine and Atmospheric Research Utrecht
Climatic Change | Year: 2015

In a recent paper Bamber and Aspinall (Nat Clim Change 3:424–427, 2013) (BA13) investigated the sea-level rise that may result from the Greenland and Antarctic ice sheets during the 21st century. Using data from an expert judgment elicitation, they obtained a final high-end (P95) value of +84 cm integrated sea-level change from the ice sheets for the 2010–2100 period. However, one key message was left largely undiscussed: The experts had strongly diverging opinions about the ice-sheet contributions to sea-level rise. We argue that such (lack of) consensus should form an essential and integral part of the subsequent analysis of the data. By employing a method that keeps the level of consensus included, and that is also more robust to outliers and less dependent on the choice of the underlying distributions, we obtain on the basis of the same data a considerably lower high-end estimate for the ice-sheet contribution, +53 cm (+38-77 cm interquartile range of “expert consensus”). The method compares favourably with another recent study on expert judgement derived sea-level rise by Horton et al. (Q Sci Rev 84:1–6, 2014). Furthermore we show that the BA13 results are sensitive to a number of assumptions, such as the shape and minimum of the underlying distribution that were not part of the expert elicitation itself. Our analysis therefore demonstrates that one should be careful in considering high-end sea-level rise estimates as being well-determined and fixed numbers. © 2015, Springer Science+Business Media Dordrecht.

Holzinger R.,Institute for Marine and Atmospheric Research Utrecht | Williams J.,Max Planck Institute for Chemistry | Herrmann F.,Max Planck Institute for Chemistry | Lelieveld J.,Max Planck Institute for Chemistry | And 2 more authors.
Atmospheric Chemistry and Physics | Year: 2010

We present a novel analytical approach to measure the chemical composition of organic aerosol. The new instrument combines proton-transfer-reaction mass-spectrometry (PTR-MS) with a collection-thermal-desorption aerosol sampling technique. For secondary organic aerosol produced from the reaction of ozone with isoprenoids in a laboratory reactor, the TD-PTR-MS instrument detected typically 80% of the mass that was measured with a scanning mobility particle sizer (SMPS). The first field deployment of the instrument was the EUCAARI-IOP campaign at the CESAR tall tower site in the Netherlands. For masses with low background values (∼30% of all masses) the detection limit of aerosol compounds was below 0.2 ng/m3 which corresponds to a sampled compound mass of 35 pg. Comparison of thermograms from ambient samples and from chamber-derived secondary organic aerosol shows that, in general, organic compounds from ambient aerosol samples desorb at much higher temperatures than chamber samples. This suggests that chamber aerosol is not a good surrogate for ambient aerosol and therefore caution is advised when extrapolating results from chamber experiments to ambient conditions.

van Angelen J.H.,Institute for Marine and Atmospheric Research Utrecht | van den Broeke M.R.,Institute for Marine and Atmospheric Research Utrecht | Wouters B.,Institute for Marine and Atmospheric Research Utrecht | Lenaerts J.T.M.,Institute for Marine and Atmospheric Research Utrecht
Surveys in Geophysics | Year: 2014

We assess the contemporary (1960–2012) surface mass balance (SMB) of the Greenland ice sheet (GrIS), its individual components and trends. We use output of the high-resolution (11 km) regional atmospheric climate model (RACMO2), evaluated with automatic weather stations and GRACE data. A persistent negative North Atlantic oscillation index over the last 6 years resulted in the summertime advection of relatively warm continental air toward the GrIS. Added to the enhanced radiative forcing by increased CO2 levels, this has resulted in an increase in near-surface temperature of more than 2 K during 2007–2012 compared to 1960–1990. The associated decrease in albedo led to an extra absorption of shortwave radiation of ∼6 Wm−2 (11 %) in the summer months, which is the main driver of enhanced surface melting and runoff in recent years. From 1990 onward, we see a steady increase in meltwater runoff and an associated decrease in the SMB, accelerating after 2005, with the record low SMB year in 2010. Despite the fact that the GrIS was subject to the highest surface melt rates in 2012, relatively high accumulation rates prevented 2012 to set a record low SMB. In 2012, melt occurred relatively high on the ice sheet where melt water refreezes in the porous firn layer. Up to 2005, increased runoff was partly offset by increased accumulation rates. Since then, accumulation rates have decreased, resulting in low SMB values. Other causes of decreased SMB are the loss of firn pore space and decreasing refreezing rates in the higher ablation area. The GrIS has lost in total 1,800 ± 300 Gt of mass from surface processes alone since 1990 and about half of that in the last 6 years. © 2013, Springer Science+Business Media Dordrecht.

Le Bars D.,Institute for Marine and Atmospheric Research Utrecht | De Ruijter W.P.M.,Institute for Marine and Atmospheric Research Utrecht | Dijkstra H.A.,Institute for Marine and Atmospheric Research Utrecht
Journal of Physical Oceanography | Year: 2012

An analysis of the Indian Ocean circulation and the Agulhas Current retroflection is carried out using a primitive equation model with simplified coastline and flat bottom. Four configurations with 0.258 and 0.18 horizontal resolution and in barotropic and baroclinic cases are considered. The wind stress is taken as control parameter to increase the inertia of the currents. The volume transport of the Indonesian Throughflow, Mozambique Channel, and Agulhas Current are found to increase linearly with the wind stress strength, and three nonlinear retroflection regimes are found. A viscous and an inertial regime had already been documented, but a new turbulent regime appears at large wind stress amplitude. In this turbulent regime, the volume of Agulhas leakage reaches a plateau because of strong mesoscale variability and, in contrast to the other regimes, does not depend on the wind stress magnitude. The physical mechanism causing the plateau is shown to be associated with the cross-jet exchange of Indian Ocean water and water from the Antarctic Circumpolar Current. In the turbulent regime, the permeability of the Agulhas Return Current to material transport increases and the Indian Ocean water available for the Agulhas leakage decreases. © 2012 American Meteorological Society.

Helsen M.M.,Institute for Marine and Atmospheric Research Utrecht | Van De Wal R.S.W.,Institute for Marine and Atmospheric Research Utrecht | Van Den Broeke M.R.,Institute for Marine and Atmospheric Research Utrecht | Van De Berg W.J.,Institute for Marine and Atmospheric Research Utrecht | Oerlemans J.,Institute for Marine and Atmospheric Research Utrecht
Cryosphere | Year: 2012

It is notoriously difficult to couple surface mass balance (SMB) results from climate models to the changing geometry of an ice sheet model. This problem is traditionally avoided by using only accumulation from a climate model, and parameterizing the meltwater run-off as a function of temperature, which is often related to surface elevation (Hs). In this study, we propose a new strategy to calculate SMB, to allow a direct adjustment of SMB to a change in ice sheet topography and/or a change in climate forcing. This method is based on elevational gradients in the SMB field as computed by a regional climate model. Separate linear relations are derived for ablation and accumulation, using pairs of Hs and SMB within a minimum search radius. The continuously adjusting SMB forcing is consistent with climate model forcing fields, also for initially non-glaciated areas in the peripheral areas of an ice sheet. When applied to an asynchronous coupled ice sheet - climate model setup, this method circumvents traditional temperature lapse rate assumptions. Here we apply it to the Greenland Ice Sheet (GrIS). Experiments using both steady-state forcing and glacial-interglacial forcing result in realistic ice sheet reconstructions. © Author(s) 2012. CC Attribution 3.0 License.

Hinssen Y.,Institute for Marine and Atmospheric Research Utrecht | van Delden A.,Institute for Marine and Atmospheric Research Utrecht | Opsteegh T.,Institute for Marine and Atmospheric Research Utrecht | de Geus W.,Institute for Marine and Atmospheric Research Utrecht
Quarterly Journal of the Royal Meteorological Society | Year: 2010

The zonal mean state of the atmosphere in the Northern Hemisphere in winter is determined by the temperature at the Earth's surface and by two potential vorticity (PV) anomalies (defined as that part of the PV field that induces a wind field) centred over the North Pole: one in the upper troposphere/lower stratosphere (UTLS), extending to the Subtropics, and the other over the polar cap in the lower to middle stratosphere. Isentropic PV inversion demonstrates that the UTLS PV anomaly induces the main part of the zonal mean wind in the troposphere, including the subtropical jet stream, while the stratospheric PV anomaly induces the polar night stratospheric jet. The stratospheric PV anomaly has a greater amplitude and extends further downwards if the Arctic Oscillation (AO) index is positive. Also, the UTLS PV anomaly has a slightly larger amplitude if the AO index is positive, but the meridional PV gradient in the Subtropics that is associated with this anomaly is greatest when the AO index is negative, resulting in a stronger subtropical jet when the AO index is negative. PV inversion translates the UTLS PV anomaly into a wind anomaly and a static stability anomaly. The resulting differences in the vertical wind shear and in the Brunt-Väisälä frequency between the two AO phases show a larger baroclinicity in the extratropics when the AO index is positive. This explains why more extratropical cyclones are observed when the AO index is positive. © 2010 Royal Meteorological Society.

Oerlemans J.,Institute for Marine and Atmospheric Research Utrecht | Van Pelt W.J.J.,Norsk Polarinstitutt
Cryosphere | Year: 2015

The climate sensitivity of Abrahamsenbreen, a 20 km long surge-type glacier in northern Spitsbergen, is studied with a simple glacier model. A scheme to describe the surges is included, which makes it possible to account for the effect of surges on the total mass budget of the glacier. A climate reconstruction back to AD 1300, based on ice-core data from Lomonosovfonna and climate records from Longyearbyen, is used to drive the model. The model is calibrated by requesting that it produce the correct Little Ice Age maximum glacier length and simulate the observed magnitude of the 1978 surge. Abrahamsenbreen is strongly out of balance with the current climate. If climatic conditions remain as they were for the period 1989-2010, the glacier will ultimately shrink to a length of about 4 km (but this will take hundreds of years). For a climate change scenario involving a 2 m year-1 rise of the equilibrium line from now onwards, we predict that in the year 2100 Abrahamsenbreen will be about 12 km long. The main effect of a surge is to lower the mean surface elevation and thereby to increase the ablation area, causing a negative perturbation of the mass budget. We found that the occurrence of surges leads to a faster retreat of the glacier in a warming climate. Because of the very small bed slope, Abrahamsenbreen is sensitive to small perturbations in the equilibrium-line altitude. If the equilibrium line were lowered by only 160 m, the glacier would steadily grow into Woodfjorddalen until, after 2000 years, it would reach Woodfjord and calving would slow down the advance. The bed topography of Abrahamsenbreen is not known and was therefore inferred from the slope and length of the glacier. The value of the plasticity parameter needed to do this was varied by +20 and -20%. After recalibration the same climate change experiments were performed, showing that a thinner glacier (higher bedrock in this case) in a warming climate retreats somewhat faster. © Author(s) 2015.

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