Research On Glacier Mass Balance And Its Relationship With Climate Change In Svalbard

Svalbard is located at the northernmost of the North Atlantic Drift. Most of glaciers in Svalbard have been classified as subpoalr or polythermal, with their areas lower than 5km2. The mass balance of subpolar glaciers in Svalbard is very sensible to climate change, and their monitoring will catch the original signal of global climate change. Based on mass balance observation in 2005/06 of two glaciers (Austre Lovénbreen and Pedersenbreen), this thesis discusses the latest variation characteristics of mass balance of glaciers in Svalbard. In addition, the history of mass balance variation of glaciers in Svalbard and its relationship with meteorological parameters have been reviewed, and the comparative studies of mass balance among Svalbard, Scandinavia and Southern Norway have been done in this thesis, in order to illuminate the characteristics of mass balance of glaciers and its relationship with climate change in a large spatial scale. The results indicate:(1) The characteristics of mass balance of glaciers in Svalbard since 1950s are summarized as follows:①There is no obvious long-term trends in annual net balance, winter accumulation and summer ablation. The annual net balance is generally negative, resulting in continuous shrinkage of glacier volumes.②T he inter-annual variations of winter accumulation are comparatively stable, while the summer ablation shows larger inter-annual oscillations. There is no indication of increased melting during the observation period.③The area/altitude distribution results in the diversity of mass balance of different glaciers. The glaciers with smaller area (<10km2) and lower altitude (<500m) retreat steadily, however, the glacier with bigger area and higher elevation is kept in zero net balance or a slightly positive net balance.④There is a good inverse relationship between net mass balance and equilibrium line altitude (ELA). No obvious change of mean mass balance gradient has been found, which means that glacial sensitivity of mass balance to ELA (or climatic) change keeps stable in Svalbard.⑤Glacier mass balance in Svalbard has close relationship with positive degree-days in July, August and September-October, as well as winter precipitation. (2) In the period of 2005/06, the characteristics of mass balance of Austre Lovénbreen and Pedersenbreen in Svalbard shows that:①The net balances of Austre Lovénbreen and Pedersenbreen are -0.83 and -0.23m i.e. respectively, total ablation are 0.98 and 0.93 m w.e. respectively, and equilibrium line altitude (ELA) are 513.27 and 530.02m respectively.②The level vector of ice flow velocity is found to converge to the central line of glaciers or be parallel to it. The average,maximum and minimum flow velocities of Austre Lovénbreen are 2.280, 3.906 and 0.814 m.a^-1 respectively and Pedersenbreen are 6.736, 8.128, and 5.490 m.a^-1 respectively. The terminus of Austre Lovénbreen has retreated with an average rate of 21.827m.a^-1, and the differences among observation sites are obvious, ranging from 77.297 to 2.758 m.a^-1.③T he vertical vector of ice flow velocity shows an effect that mass is lost in the ablation area. This effect is weakened with the increasing altitude. Besides, Austre Lovénbreen shows an effect that mass is gained at the profile of E.(3) The mass balance of glaciers in Svalbard, Scandinavia and Southern Norway and their response to climate change show that:①Glacier mass balance in Svalbard has the characteristics of low annual amplitude and small interannual variability. By contrast, glacier mass balance in Scandinavia and Southern Norway show large annual amplitude and interannual variability, and mass balance process of glaciers at these two areas shows the characteristics of positive oscillation.②Glacial sensitivity of mass balance to ELA (or climatic) change is related with its state of mass balance: the more positive glacier mass balance, the higher sensitivity, and vice versa. In average, mass loss of glaciers in Svalbard, Scandinavia and Southern Norway during the monitor period is equivalent to a rising of 0.32°C of air temperature in relation to zero net balance. The highest temperature increase is found in Svalbard with 0.55°C, and only a rising of 0.12°C is found in Southern Norway.③The net balance sensitivity to air temperature increase of +1°C ranges from -0.42 to -0.99m w.e.·a^-1, and the net balance sensitivity to snow precipitation increase of +10% ranges from +0.01 to +0.57m w.e.·a^-1. The summer balance sensitivity to air temperature increase of +1°C varies from -0.43 to -0.87m w.e.·a^-1. The winter balance sensitivity to snow precipitation increase of +10% ranges from +0.07 to +0.31m w.e.·a^-1. For average, 24% increase of snow precipitation is needed to offset the loss of net mass balance induced by air temperature increase of 1°C. The sensitivities of glacier mass balance with respect to climatic settings (continental/maritime) show that maritime glaciers have comparatively higher sensitivity than continental galciers.