The Research On Subglacial Geophysical Characteristics Of Princess Elizabeth Land In East Antarctic

In the past century,the global sea level has risen by 19 cm,mainly due to ice melting and sea water expansion caused by the temperature rise.Glaciers and ice sheets are shrinking and it is expected that by 2050 the Arctic will become an almost ice-free area,and the ever-increasing sea level is threatening human habitat.Antarctic glaciers are likely to change the global sea level by a few meters under the influence of climate change over the next few centuries.Therefore,it is very important to study the influence factors of the ablation and accumulation of the Antarctic ice sheet,especially the subglacial bedrock structure and its thermodynamic characteristics.In addition to a small amount of ice core drilling and the underwater robot sampling below coastal ice shelves,only through the geophysical approach to understand the ice sheets and the deep state of bedrock.Princess Elizabeth Land(PEL)is the highest elevation area in Antarctica and is covered by ice sheet up to 4km,and little is known about the subglacial structure.In December 2015,the author joined the aerogeophysical exploration project team of CHINARE 32 to carry out our first Antarctic aerogeophysical survey by China’s newly purchased snow eagle 601 fixed-wing aircraft in PEL.Based on the data of 29 aerogeophysical lines,this paper analyzes the geophysical characteristics of the ice sheet and bedrock under the PEL.The analysis of the regional bedrock canyon and ice-rock interface is based on the aerial ice-penetrating radar data.The distribution status of the water system and the regional crustal equilibrium state is based on the gravity data under the radar constraint.The influence of the curie interface fluctuation on the geothermal flux distribution is discussed based on the aeromagnetic data.Ice radar detection is currently the main means of understanding the subglacial terrain fluctuation.The world of Antarctica ice radar detection has covered most of the Antarctic ice sheet area,but PEL currently has only four ice radar profiles.The understanding of the regional terrain is basically inferred from the fine elevation difference of the ice surface based on the satellite data,and can not accurately get the fluctuate of the bedrock interface.Especially the structure of the subglacial canyons and basins,there are problems of human subjective understanding.China’s ice radar detection of Antarctic ice sheet research started late,at present only from Zhongshan station to Kunlun station along a route of multiple ground ice radar measurement.Only a single observation area and the capacity of data processing and analysis is insufficient.In this paper,we combined with China’s first airborne ice radar detection,analysis the data characteristics of ice radar data and processing data with properly method.Summed up a set of processing methods which is conform to the ice sheet characteristics from the airborne ice radar data.Combined with the semi-automatic interface extraction method under the artificial intervention to maximize the accurate ice/ice and ice/rock interface conditions.This paper analyzes the formation of the canyon in the study area and analyzes the main causes of it.It’s the first time proved the big canyon under the ice sheet of PEL,quantitative characterization of the canyon features and analysis the detailed structure.Inversion of density interface fluctuation using gravity data is an important task to explain the characteristics of geological structure.Based on the structural characteristics of the ice sheet-lake water-bedrock in the Antarctic subglacial lake area,this paper proposes a three-dimensional interface inversion method based on the known depth point constraint obtained by ice radar detection,which makes the gravity interface inversion result more accurate.At present,the analysis of the ice surface by satellite altimetry data shows that there may be a large subglacial lake under PEL,and the satellite data only supports the general estimation of the scale of the lake.Based on the aerial ice radar and aerial gravity data,this paper use the three-dimensional gravity interface inversion method under radar constraints to invert the subglacial lake and obtain its structural characteristics.The results show that this lake is only part of the narrow subglacial lake,and it is likely to become the second large subglacial lake in Antarctica,which is just after the largest one-Lake Vostok.We analysis the subglacial water system combined with the intertwined relationship between the subglacial canyon and water.The results show that the inland upstream is the distributed form,the system drainage efficiency is not high,tend to increase the ice sheet sliding along the ice bed interface.To the north,it is gradually changed to channel form.The water flow increases and accelerate the drainage to the coastal areas.The water network does not substantially affect the basic lubrication of the ice/bedrock interface.The isostatic gravity anomaly is closely related to the vertical gravity balance compensation movement of the crustal,and the stability of the regional crust can be understood through the isostatic state.PEL is widely distributed in subglacial mountains,which is up to 3000 km above sea level.With the area’s huge overlying ice sheet,the isostatic state of the crust has a great impact.This paper calculates the isostatic gravity anomaly of PEL by the Erie isostatic model,and analyzes the crustal isostatic state of this area.The results show that the region is negative isostatic anomalies,the southern inland negative anomalies are very large,which is most likely due to the ablation of ice sheet produced a strong imbalance force,to promote the crust rising and thicken to supplement the ice loss.The Curie surface as a global distribution geophysical interface inner the earth,it is related to the thermal characteristics of continental crust.The results show that the PEL’s isothermal Curie surface is shallow.The performance is the large surface heat flux accelerate the melting of the bottom ice.So,we can understand the deep crustal factors of the widely distributed water system here.