Analysis of change in extent of glacier based on DPSIR model
Since 68.7% of the world fresh water is frozen in ice, glacier has significant meaning in global climatic and ecological stability (The USGS Water Science School, 2016). However, more and more data has shown that glacier is retreating along with the exponentially rising global temperature. The retreat of glacier results in many environmental problems. One main concern is that ice melting causes global sea-level rise. Retreat of glacier is also strongly connected to the fresh water supply. As our society is threatened by water supply security and global sea level rising, the relationship between human and glacier is worth paying attention. Driver-Pressure-State-Impact-Response model adopted by European Environmental Agency is a framework that studies the society-environment relation. This article is going to analyze the change in extent of glacier based on DPSIR model. It will discuss the driver force of glacier retreat and the pressure that glacier retreat brings to the environment and therefore, the current situation that we are facing this pressure and the impacts that glacier retreat brings to the society. In the end, some response on how we can change our activities in order to slow down the glacier retreat and reduce its impacts will be discussed.
1.Historical Glacier Extent and Pressure
Studies has shown that there have been five known ice ages in the Earth’s history. At present, we are experiencing the Quaternary Ice Age which started roughly 110,000 to 12,000 years ago (Marshall, 2010). Currently, the earth is in an interglacial period of Quaternary Ice Age, and ice sheets which are remnants of the last glacier period started to melting and now glaciers only cover 10% of the earth surface. (Gradstein, Felix; et al. 2004). The majority of ice sheets are located in Greenland, Antarctica and other mountain regions. Between 1550-1850, the earth experienced a cooler period which is called Little Ice Age (Oosthoek, 2015). Since 1850, the rate of glacier retreat became remarkably because human activities lead to global warming (NASA, 2003).
- Current State
One commonly used data for measuring glacier extent is the glacier mass balance (Bierman and Montgomery, 2014). Since glaciers losing more mass than they receive will be in negative mass balance and so will retreat, the change in glacier extent can be indicated by glacier mass balance (Davies, 2016). According to the World Glacier Monitoring Services, a strong mass loss of global average cumulative mass balance is recorded in the first decade since the start of measurement which is 1930. The rate of glacier mass loss was fast in the first decades. But it slowed down between 1956 to 1965. During 1966 to 1985, the global glacier lost ice mass at a moderate rate. From 1985 to 2014, the rate has been accelerating (Zemp, et al., 2015).
Figure 1: global average of observed mass balance from 1930 to 2013. Cumulative annual averages relative to 1960
Sources: The World Glacier Monitoring Services The Global Glacier Chang Bulletin p9
3.Impacts of The Shifts in Extent of Glacier
3.1 Impact on Human Society
Given the fact that the retreat of glacier is keep growing, there are many environmental and social problems which are and will be resulted from this issue. One major concern of retreat of glacier is that global sea level will be pushed up by retreat of glacier.
From 1993 to the end of 2006, highprecision satellite altimeters pointed out that the global average sea level has been rising at 3.1 ± 0.4 mm year-1(Beckley et al. 2007). The rate of sea level rise is faster than the average rate of rise in the 20th century. The magnitude of it is larger than the rate of rise over the two millennia prior to the 18th century (Church, J.A. et al., 2008). One possible driver force for the sea-level rise could be that much amount of water which is stored in solid state (ie. glacier) has been transformed into liquid state because of melting. Meier states that rapid retreat and thinning of marine-terminating glacier are primary driver of recent ice loss. In his report published in 2007, he stated that Currently, 1.88mm/year of sea-level rise is generated by glacier and ice sheet wastage. The author predicts that due to the temperature in cold polar and subpolar glacier rises, the contribution of ice wastage to sea-level rise will be likely to increase in the future (Meier, M. F et al., 2007)
Later, a report that concentrates on more recent period (2003-2009) has shown that the global glacier mass budget was –259 ± 28 gigatons per year. Combined loss from ice sheet contributes to 29 ± 13% of the observed sea level rise (Gardner, A.S. et al.,2013). Series of research indicates that contribution of ice melt to global sea level rise is increasing. Therefore, if glacier keeps retreating at the current rate or even faster, many cities located along coastlines will be drown. Neumann with his colleagues state that in 2000, 10.9% (625 million) of world population live in LECZ (low elevation coastal zone). And according to their estimate, population in LECZ is likely to keep increasing and reach 1.4 billion people by 2060. When we review the history of human society development, it is notable that people always tend to settle down in coastal regions due to the rich resources, convenient geographic position for trade and transport of coastal zones (Neumann B et al, 2015). Since coastal zones develop at a rapid pace, society in coastal cites is becoming increasingly vulnerable to sea-level rise (Church, J.A. et al., 2008). As a result, infrastructure in coastal cities would be strongly affected by natural disasters driven by sea level rise. More seriously, a large amount of population need to migrate and may lose their homes.
Apart from the sea level rise, water availability is also highly connected to the retreat of glaciers and many social problems could be caused by change in water resource availability. Under the background of glacier retreat, server water scarcity may occur at the areas where majority activities rely on ice water melt runoff in warmer summer months. Although in short term, the increasing ice melting could increase the summer water supply. In the long run, since glacier will lose mass because of the glacier retreat and eventually disappear, ice water will be eventually depleted(Zhang, J et al., 2012). Runoff of rivers will be decreased since it loses the ice melt water supply. Thus, the ability of rivers to irrigate crops and regulate climate will be affected. Besides, summer river flows which is vital for keeping dams and reservoirs is decreased. Such a problem is especially serious in South America because in South America many artificial lakes are filler by glacial melt (BBC, 2003).
3.2 Impacts on Nature
Shifts in extent of glacier not only influence human society, but have important effects on nature as well.
Biodiversity has been threatened by the results of glacier retreat. In polar regions where the land surface is largely covered by ice, wildlife is particularly threatened by reduced ice extent (Assessment, M. E. 2005). The environment in polar regions has been shifted obviously over the last century. 14% of Arctic sea ice has disappeared since 1970 (WWF Global, 2016). Changing living conditions could impact wildlife severely. Take the average weight of female polar bears for example, in 1980, research stated that average weight of female polar bears in western Hudson Bay, Canada, was 650 pounds. Yet their average weight reduced to only 507 pounds by 2004 (NASA, 2006). Scholar (e.g. Djoghlaf, 2008) believed that the reduction in polar bears’ average weight is associated with gradually earlier breakup of the Arctic sea ice because ice mass loss led to shorter hunting season for bears and therefore, less food intake.
Last but not least, as glacier retreats, ice coverage reduces. The reduce of ice coverage on earth, especially polar regions that are covered by ice sheet, will lead to a significant change in global climate. A large portion of short wave radiation that comes from the sun is originally reflected by ice sheet since the ice sheet with white-color has relatively high reflectivity compared to other landforms. As about 69% energy is reflected, the temperature of earth surface is pulled down notably. Yet, as global temperature increases, there is reduction of ice sheet coverage because high temperature results in ice melting. Therefore, less radiation will be reflected due to the shift in ice coverage and earth surface temperature will be increased. Consequently, the rate of global temperature rising will be accelerated. A positive feedback loop is generated, and the rate of temperature increases will keep growing. One of the important effects of the retreat of glacier is that this positive feedback loop will keep aggravating the extent of global temperature rising, and many server environmental and social problems will be driven by global temperature rising (Oke, 2002). A report from WWF Global in 2007 has already revealed that the additional heat that is absorbed because of decreasing ice coverage on Arctic Ocean in summer has already been accelerating both regional and global warming and preventing sea ice from recovering (WWF Global, 2016). Furthermore, some scholars concern that the increasing temperature caused by arctic feedbacks might significantly enough to alter climate feedbacks in other regions (Sommerkorn, M., & Hassol, S. J. 2009). The retreat of glacier is worth much concerns not purely because this issue has some direct effects on regional environment where glacier located. In addition, since it will lead to faster global temperature increasing and shifts in climate feedbacks in other regions, many indirect effects that are caused by global temperature increasing are also strongly threatened out surviving conditions.
- Response
Under the background of global warming, how the extent of glacier will be shifted is a question that many of us are concerned. However, it is difficult to predict the trends of glacier in the future because there are many questions to be solved. For example, if glacier will entirely disappear in the future as the global temperature keeps rising. Although stream runoff will increase immediately as ice melts, runoff will be decreased eventually and when this infection will occur. The biggest obstacle for answering these question is uncertainty. According to DPSIR model, human society is influenced by the changing environment, yet the environment is also changing by our response. Suitable strategies can be posed in order to alter the driving force of glacier retreat and adapt to the changing condition caused by glacier retreat. Many climate policies have been stressed out the mitigation for the environmental issue that we are facing now. But recently, a shift in emphasis on adaptation has been noticed with the inevitable change in climate which is mainly expressed as global warming (IPCC, 2014).
4.1 mitigation
The International Panel on Climate Change (IPCC) defines mitigation as: “An anthropogenic intervention to reduce the sources or enhance the sinks of greenhouse gases.” According to IPCC in 2014, there are many differences between mitigation and adaptation. Mitigation relies on collective action among countries to work together so that the issue that threaten humans might be mitigated (Victor, 201). To mitigation glacier retreat, one feasible strategy is to mitigate the driving force which is global warming. IPCC suggested some national and sector policies for mitigation. For example, large changes in investment pattern that lead to substantial reduction in emission; using regulatory methods and resources management; regulating the private sector which play important roles in the process of emission and mitigation (IPCC, 2014).
4.2 Adaption
Different from mitigation, adaptation refers to the ability that a system can adjust to the changing environment to moderate potential damage (Global Greenhouse Warming, 2016).
Compared to the mitigation requiring collective action from different countries, main adaptation strategies have local scale (Victor, 2011). As discussed in 3.1, one of most important effects that glacier retreat can bring to human society is sea-level rise. However, if local government implement proper adaptation strategies, society in costal zones can adjust to changing environmental conditions and moderate potential damage. A good example is the City of Cape Town. As a coastal zone city, The City of Cape Town administers around 307km of coastline. Coast provides a series of social-economic opportunities. However, based on the circumstance that sea-level is rising due to glacier retreat, significant impact may be applied on coastline. Cape Town could be particularly vulnerable due to its extensive coastline (Mukheibir, P., & Ziervogel, G. 2007). In a report published in 2008 by Cartwright, some possible adaptation strategies were shown. For example, spending more expenditure on coastline defense in case of coastal erosion and flooding; maintaining drains and stormwater system and incorporating. sea-level rise risks in disaster management strategies (Cartwright, & Fairhurst, 2008).
Conclusion:
Human activities, especially after 1850, has accelerated the rate of glacier retreat. On the other hand, glacier retreat also threatens human society. Based on DPSIR model, the impacts of retreat of glacier and our response to glacier retreat interact with each other. The state of environment is dynamics because of this interaction. Hence, there are many uncertainties about the future of human-glacier relationship. If we change our production pattern and make more sustainable choice, the driver of glacier retreat might be altered. By implementing mitigation and adaptation strategies, the rate of glacier retreat might be slow down and people could have more time to reply the effects of climate change.
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