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Melting ice sheets in Greenland contribute 25% to sea level rise

Recently we reported the loss of snow cover in Europe. The snow is not only gone in many parts of Europe, also Greenland’s ice cover is melting. The Greenland ice sheet contributes 25% to global sea-level rise. This makes it the largest contribution of the cryosphere. The increased mass loss of Greenland ice during the 21st century is mainly due to the increased surface water runoff, of which ~93% come directly from the small ablation zone of the ice sheet (~22% of the ice surface). As the snow melts in the summer, bare glacier ice is more exposed in this ablation zone. Naked ice is darker and less porous than snow. It absorbs more than twice the solar radiation while also holding back less meltwater. Smooth ice produces a large proportion (~78%) of the total outflow of Greenland into the sea, although in summer only a small area of ​​the ice is exposed. Accurately capturing the reduced albedo and the full extent of bare ice in climate models is critical to determining Greenland’s present and future runoff contribution to sea-level rise.

The mass loss of the Greenland ice sheet has recently increased due to the accelerated melting of its surface. As this melting is critically affected by surface albedo, understanding the processes and potential feedbacks regardinng the albedo is required for accurately forecasting mass loss. The resulting radiation variability of the ablation zone caused the ice layer to melt five times faster compared with hydrological and biological processes, which also darken the ice sheet. Variations in the snow limits due to the shallower ice layer at higher altitudes have an even greater impact on melt when the climate is warmer. As a result of these fluctuations, the mapped ice surface during the summer of 2012, the record year of snowmelt, was the largest and had an area of 300,050 km2. That is, bare ice accounted for 16% of the ice surface. The smallest extent of bare ice was 184,660 km2 and was observed in 2006. This corresponded to 10% of the ice surface, i.e. almost 40% less area than in 2012. However, the observed snowpack variation was high and the observation period was too short for a solid trend assessment.

Current climate models are too inaccurate in predicting the sea level rise during flood years, leading to uncertainty in the estimation of Greenland’s contribution to global sea level rise. To understand the factors that influence melting, Jonathan Ryan of Brown University, Providence, Rhode Island, and his colleagues have investigated Greenland’s snow line. At altitudes below the snow line, the darker ice is not covered by snow. This snow line moves up or down during Greenland’s seasons. The researchers mapped these movements between 2001 and 2017 using satellite images. The average height of the snow line at the end of the summer in 2009 was between 1,330 m and then 1,650 m in 2012. The fluctuations in the snow line are the most important factor when it comes to how much solar energy the ice sheet absorbs. Modelers must consider this effect to improve their predictions. Knowing how much and how fast the Greenland ice melts will help us to take better protective measures. At Frontis Energy, we think that the best protection against sea-level rise is the prevention and recycling of CO2.

(Photo: Wikipedia)

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Economic losses caused by flooding due to global warming

In Europe, floods are linked to high fluctuations of atmospheric pressure. These variations are also known as the North Atlantic Oscillation. Stefan Zanardo and his colleagues at Risk Management Solutions, London, UK, analyzed historical records of severe floodings in Europe since 1870. They compared patterns of atmospheric pressure at the time of the floods. When the North Atlantic Oscillation is in a positive state, a depression over Iceland drives wind and storm throughout northern Europe. In a negative state, however, it makes southern Europe moister than usual. Normally, floods occur in northern Europe. They cause the most damage if the North Atlantic Oscillation was positive in winter. If enough rain has already fallen to saturate the soil, high risk conditions for flooding are met. Air pressure in Europe may change with global warming and public administrations should take this into account when assessing flood risk in a region, the researchers say.

This is important because flooding in Europe often causes loss of life, significant property damage , and business interruptions. Global warming will further worsen this situation. Risk distribution will change as well. The frequent occurrence of catastrophic flooding in recent years has sparked strong interest in this problem in both the public and private sectors. The public sector has been working to improve early warning systems. In fact, these early warning systems have economic benefits. In addition, various risk mitigating strategies have been implemented in European countries. These include flood protection, measures to increase risk awareness, and risk transfer through better dissemination of flood insurance. The fight against the root cause, global warming that is, however, is still far behind to what is needed.

Correlations between large-scale climate patterns, and in particular the North Atlantic Oscillation, and extreme events in the water cycle on the European continent have long been described in the literature. With with more severe and more often flooding as well as alarming global warming scenarios, raising concerns over future flood-related economic losses have become the focus of public attention. Although it is known that climatic patterns also control meteorological events, it is not always clear whether this link will affect the frequency and severeness fo flooding and the associated economic losses. In their study, the researchers relate the North Atlantic Oscillation to economic flood losses.

The researchers used recent data from flood databases as well as disaster models to establish this relation. The models allowed the quantification of the economic losses that ultimately caused by the North Atlantic Oscillation. These losses vary widely between the countries within the influence of the North Atlantic Oscillation. The study shows that the North Atlantic Oscillation can well predict the average losses in the long term. Based on the predictability of the North Atlantic Oscillation, the researchers argue that, in particular, the temporal variations of the flood risks caused by climate oscillations can be forecast. This can help to take encounter catastrophic flood events early on. As a result, flood damage can be minimized or even avoided. As scientists improve their predictions for the North Atlantic Oscillation, society will be better prepared for future flooding.

(Photo: Wikipedia, Stefan Penninger, Sweden)