Glaciers And Climate Change Environmental Sciences Essay

The article is mainly talk about the interaction between glaciers and climate change. Take the Tianshan No.1 Glacier as an example. Glacier produces in climate and by the impact of climate change. The glaciers change is the result of climate fluctuations. And glacier changes in turn acts on the natural environment that contribute to climate change. Tianshan No.1 Glacier has changed significantly in the past five decades, includes glacier surface firn characteristics, ice formation zones, ice temperature, thickness, area and terminus position, etc. These glacier changes related to temperature rise, and respond to recent climate variation. In addition, changes in the global climate and environment caused by glacier change, such as the increase of glacier runoff, sea-level rise, and the reduction of surface albedo caused by area shrinkage etc. The interaction between glacier and climate change not only has important impacts on global climate variation, but also has great significance for the study of climate and environment.

1. Introduction

Glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation (melting and sublimation) over many years, often centuries. Its movement caused by the action of gravity. Glacier ice is the largest reservoir of freshwater, supporting one third of the world’s population. 11% of the world’s land area is covered by glaciers. The glacier mainly distributed in the Antarctic, the Arctic and high-altitude regions of the middle and low latitudes. It is a product of the climate and a good indicator of climate, also it acts on climate. The glaciers change, especially changes in mountain glaciers, is a barometer of global climate change. Precipitation, temperature is the main climate factors that affecting glaciers. The precipitation decides glacier accumulation, and temperatures decide ablation. Therefore, the amount of precipitation, its distribution during the year, and interannual variability effect glacier recharge and activities. While the temperature impacts ice formation and glacial melt water. The precipitation and temperature codetermine the nature of the glacier, development and evolution.

1.1 Glacier mass balance

Glacier mass balance is the key factor that links glacier fluctuations and climate change. Climate change leads to corresponding changes in the material balance state of glacier. While this kind of change in the mass balance of glacier can lead to change in glacier movement characteristics and glacier thermal regime, and thus lead to changes in the glacier terminus position, size and ice reserves.

Glacier mass balance formular has two elements: glacier accumulation and ablation. Glacier ice accumulation occurs through accumulation of snow and other frozen precipitations, include rime ice, avalanching from hanging glaciers on cliffs and mountainsides above, and re-freezing of glacier melt water as superimposed ice. The ablation refers to the melting of snow or ice that runs off the glacier, evaporation, sublimation, calving, or erosive removal of snow by wind. Air temperature is typically the dominant control of ablation with precipitation exercising secondary control. With successive years in which accumulation exceeds ablation, a glacier will experience positive mass balance, its terminus will advance and vice versa.

1.2 Research Significance

Current glacier recession under the global warming has aroused world-wide attention. The sensitivity of alpine glaciers to temperature change is found to be largely amplified. The number of retreating glaciers has improved significantly. For a number of glaciers, shrinkage rate appears to have accelerated since the 1990s. Increase melting speed of glaciers can lead to sea level rise and submerging of some coastal areas. Moreover, it induces snow and ice related disasters, for example, glacier flood and avalanche, which menace the living environment of human beings and wild animals, as well as change the habits and characteristics of many species. On the other hand, the disappearance of ice-covered regions on the Earth will in turn change the global climate regime significantly. Ice covers, especially those in the Polar Regions, can reflect a great deal of solar energy back to the outer space, which helps to keep the Earth cool. However, with the ice cover melting, the underlain land and the water will expose to the air, and thus certainly absorb much more solar radiation and cause more ice melting. The accelerated glacier recession in China is also very obvious, especially in Northwest China, where glacier melt water runoff increases, area of glacier decreases, terminus retreats, snow line elevates and many small glaciers are disappearing. Glacier is known as the solid reservoir and the cradle of oasis in the arid regions in Northwest China. It is the major water source for human living and development.

Study area

Tianshan No.1 Glacier(43°6′N¼Œ 86°49′E) is located at a height of 3,454 m above sea level, and about 118 km from Urumqi, the capital of Xinjiang Uygur Autonomous Region in China. It is the headwaters of Urumqi River, approximately 100km from Asia geographic center. In addition, it is considered one of the most important dry land glacier models in Asia, and one of the most famous ten glaciers in the world.

It has the longest record of mass balance in the Asian high mountains. The glacial record shows that the glacier has shrunk significantly in last 30 years. The Tianshan No.1 glacier is shrinking at the speed of 3.5 m and 5.9 m every year on its east and west sides respectively. In the past 45 years, its coverage has dropped from 1.94 sq km to 1.68 sq km, a 13.8% loss. The land here is characteristic of alluvial deposits by glaciers, so those conducting geological surveys can explore the development course of the Urumqi River in the past millions of years.

Glacier-climate interactions

The glaciers change is the inevitable result of climate fluctuations. Atmospheric precipitation and heat status changes, profound impact on the growth and decline of the advance and retreat of the polar ice caps and mountain glaciers. By observing the glacier changes, understanding the glacier dynamic of global or regional, and forecasting global climate change. Glaciers in China are mainly small and medium-sized mountain glaciers in low latitude. They have a good response for climate fluctuations of short cycle.

Since the Little Ice Age, the general trend of glaciers around the world is retreat mainly. The Fourth Assessment Report of IPCC (Intergovernmental Panel on Climate Change) pointed out that impacts of climate warming on many phenomena are remarkable, such as shrinkage of the Arctic ice cap, acceleration of sea level rise, recession of glacier terminus all over the world, thawing of permafrost, earlier breaking up of ice in the rivers and lakes, prolongation of crop growing season in the middle and high latitudes, and changes in the distribution and behavior of animals and plants.

Take Tianshan No.1 Glacier as an example, glacier has changed significantly in the past five decades, includes glacier surface firn characteristics, ice formation zones, ice temperature, thickness, area and terminus position, etc.

The main drive forces to the glacier change are the heat and water conditions of the glacier covered region. Glacier melting is tightly related to the temperature variation. According to the records of meteorological stations in the headwaters region, the air temperature has been rising since 1985, and the tendency of rise has accelerated since 1995. From 1997 up to present, the average temperature has increased by 1℃, as the largest rise extent in recent 50 years. The observation of Daxigou Meteorological Station shows that the average annual temperature increased by 0.8℃(0.017℃/a) during 1958~2004 with obvious temperature rises especially in autumn and winter.

The characteristics of snow-firn stratigraphy and ice formation zone of the glacier are sensitive to the climate change. The climate warming greatly promotes the glacier melting, which consequently alters the properties of snow pack stratigraphy and ice formation zones. According to the analyses of 60 vertical profiles of snow pits obtained from the accumulation zone of Tianshan No. 1 Glacier during the period of 1961~2005, the construction of snowfirn stratigraphy had a remarkable change. The proportion of coarse firn in the snow pits increased from 40% to 65%, and fine firn decreased from 25% to 7%. This indicates that snow pack is severely affected by melt water, which accelerates the process of transformation from fine firn to coarse firn. Compared with the snow-firn stratigraphic constituents and its structure in the 1960s and 1980s, current specimens show remarkable changes, such as reduction of snow-pack depth, simplification of structure, blurred boundaries of snow layers, and mergence of dust layers within snow pack.

The mass balance change is an undelayed response of the glacier to climate change, and it is a sensitive indicator for climate change. For the mass balance of Tianshan No. 1 Glacier, both annual value and cumulative value have shown negative increases since 1958, indicating severe mass losses. In time of 1958-2004, there were 31 negative mass balance years against 15 positive years. From 1997 to today, the negative mass balance has lasted for 10 years, which never happened ever before. The average annual mass balance during 1958-2004 was -233.6 mm water equivalent (weq) and the cumulative mass balance added up to -10746.5 mm weq, which means that the average thickness of the glacier nearly reduced 12 m and the volume loss was about 20.62-106m3 weq.

Unlike the glaciers in Europe and mid-America, which accumulate in winter and lose mass in summer, Tianshan No. 1 Glacier has both accumulation and ablation in summer, and there is little snowfall in winter. Previous researches on Tianshan No.1 Glacier have shown that the mass balance was connected with the precipitation, and negatively correlated with air temperature in summer (May to August). However, with the increase in both current temperature and precipitation, mass balance has different responses to them.

Retreat of glacier and its impact

Under the climate warming, the law of terminus recession and ice thickness reduction are followed by glacier shrinkage. The changes of glacier area and terminus position result from short-term and long-term climate changes. Tianshan No. 1 Glacier has an overall shrinkage since the year 1959 when the observation initiated. The east and west branches of Tianshan No. 1 Glacier separated into two independent glaciers in 1993 due to ablation, during this period (1959~1993) the total terminus retreat was observed as 139.72 m at an average retreat rate of 4.5 m per year. From 1993 to 2004, the east branch of Tianshan No. 1 Glacier retreated at an average rate of 3.5 m per year (a total of 38.7 m), and the west branch retreated at a rate of 5.8 m per year (a total of 64.1 m). The recession rate (the ratio of receded length to the original glacier length) of Tianshan No. 1 Glacier was 7.8% in the period of 1962~2004 for the east branch and 10.5% for the west branch, respectively. The west branch terminus retreated 6.92 m in 1999 and 6.95 m in 2000, respectively, which are the highest records in the observation records. Since the ice flow velocities in corresponding years were observed stable at terminus, it is unlikely that the significant retreats were caused by the reduction of ice flux from upper parts of the glacier, and thus, it is clearly due to the intense ice melting. With terminus receding, its altitude simultaneously elevated from 3736 m a.s.l in 1962 to 3746m a.s.l in 1980, and the east branch terminus altitude in 2005 was 3777 m a.s.l, 31 m higher than that in 1980. Glacial ablation will not only lead to floods, landslides and other natural disasters, but also lead glacier runoff also to be reduced, and make the downstream freshwater resources gradually scarcity.

Research

Cumulative temperature is a major factor affecting glacier ablation. Cumulative temperature, namely, the sum of daily mean air temperature above the melting point during ablation season is closely related to the area of glacier ablation zone. According to the previous studies, the annual cumulative temperature in the headwaters region of Urumqi River rose by 133℃•d during 1960~2004. Its tendency is coincident with that of average annual temperature, i.e. since the late 1980s the cumulative temperature has risen remarkably, and meanwhile the climate warming showed a accelerated tendency (see Fig.1).

Fig. 1 Mass balance of Tianshan Glacier No. 1, accumulated temperature (T¼ž0℃) and their trends during 1958~2003

During the period of 1962~2006, the area of Tianshan No. 1 Glacier reduced by 0.27 km2. From 1992 to 2006, the glacier area decreased by 0.16 km2, which is 0.04 km2 more than that from 1962 to 1992. Based on the observation over the past 43 years, glaciologists found that the decrease of glacier area has accelerated since 1986. Figure 2 shows the recession process of the glacier terminus, and Fig. 3 displays the morphological shapes of Tianshan No. 1 Glacier in different years.

Fig. 2 Morphological change of Tianshan No. 1 Glacier over time.(Dashed lines represent the glacial boundaries of 1962, 1973,1980, 1984, 1986, 1994 and 2001; solid lines represent the glacial boundary of 2006)

Fig. 3 Morphological changes of Tianshan No. 1 Glacier in the years of 1962, 1988, 1993,1996, 2001, and 2005

Glacial temperature, especially the temperature of the ice below active layers, determines many physical characteristics of the glacier. The change of ice temperature indicates the change in the glacier’s cold reserve, which can cause the change of the sensitivity of the glacier in answer to climate warming. Comparing with three vertical profiles of ice temperature at the altitude of 3840 m in the years of 1986, 2001 and 2006 (Fig. 4), The glaciologist found that it is about 10m in depth that the lower boundary of the active layer of the glacier, below which the ice temperature is little affected by the seasonal variation of air temperature. If ignoring the change of the ice temperature in active layer, the ice temperature from 10 to 22 m in depth had a remarkable rise during 1986~2001. The rise range decreased with the largest value of 0.9℃ (10%) at 10 m depth below ice surface and a negligible change at 22 m depth. Similarly, compared with the ice temperature in 2001, the ice temperature in 2006 had an obvious rise, with an increase of 0.4℃ at 10 m depth. Usually, the ice temperature at the lower boundary of active layer is identical with the annual average air temperature. Therefore, the rise of ice temperature is undoubtedly the result of progressively climate warming.

Fig. 4 Comparison of ice temperature profiles obtained in 1986, 2001 and 2006 at a site around 3840 m a.s.l on No. 1 Glacier in Tianshan Mountain

Fig. 5 Annual mass balance of Tianshan No. 1 Glacier against summer temperature (May-August), annual temperature and annual precipitation at Daxigou Meteorological Station

Figure 5 shows the variations of mass balance, summer temperature, annual temperature and precipitation during1959-2004, from which researcher found that during 1960-1986 the mass balance had a weak negative correlation with temperature, while a clear positive correlation with precipitation, indicating that the mass balance is controlled by both temperature and precipitation, with precipitation as the main factor. During this period, the annual average temperature and precipitation were -5.4℃and 425.8 mm, respectively. However, the correlation has altered since 1986. The mass balance showed a negative correlation with temperature and no correlation with precipitation, indicating that the mass balance was mainly controlled by temperature. During this period, average annual temperature and precipitation were -4.9℃and 491.6 mm, respectively. The results show that temperature and precipitation are usually control mass balance, but temperature is mainly control mass balance when temperature rises to a certain level, though with high precipitation.

Existing policy for climate change adaptation

As early as in 2006, the Urumqi municipal government had made ​​provisions: from pollution to protect important water source in Urumqi, prohibit visitors in Tianshan Glacier. But the absence of fencing and secure, some tourists into the glacier region through various ways, changed the environment of the glacier. The deputy of autonomous regions, Chunyu Cui, proposed to establish an areas about National Tianshan Glacier nature reserves of Xinjiang in 2012. But the policy had not yet been introduced.

Conclusions and recommendations

Conclusions

Taking Tianshan No. 1 Glacier as an example, this article talk about the response of glacier to current climate warming based on the observation dataset of 50 years. The conclusion was drawn as follows:

Since the 1960s, snow firn stratigraphic components and structure have shown remarkable changes, including reducing snow pack depth, simplifying structure, and obscuring boundaries of snow layers with different characteristics. The area of glacier ablation zone keeps expanding, the positions of ice formation zones move upwards, and the top of east branch has already shown the characteristic of ablation zone.

During 1962~2006, the area of Tianshan No. 1 Glacier reduced by 0.27 km2 (14%). The shrinking tendency has accelerated in recent years. At the altitude of 3840 m a.s.l, a significant rise in the ice temperature was observed during 1986-2001, with the highest rise value of 0.9℃ at depth of10 m. From 2001 to 2006, the ice temperature rose by 0.4℃at depth of 10 m.

Average annual mass balance during 1958-2004 was -233.6 mm weq, with the cumulative mass balance of-10746.5 mm weq, which indicates that the thickness of Tianshan No. 1 Glacier reduced nearly 12 m and loss of volume came to about 20.62-106 m3. Mass balance is controlled by both temperature and precipitation before 1986, with precipitation as the main factor. But after 1986, mass balance is controlled mainly by temperature, though with high precipitation.

Recommendations

In order to protect the glaciers, many experts hope to take measures as soon as possible to protect the natural environment of the glaciers in Xinjiang in accordance with the law, slow down man-made destruction. On the other hand, encourage and support to use the artificial weather fully developed air water resources, to carry out the artificial water project, in order to increase the glaciers snow.

There are some suggestions:

Through energy conservation, development of natural gas, hydropower, coal bed methane utilization, bio-energy, wind energy, solar energy, geothermal energy. Strengthen the planning and implementation of ecological construction and environmental protection.

Strengthening climate change communication and scientific popularization to raise awareness of climate change in the whole society.