regime of selected glaciers in S Spitsbergen derived from radio echo-soundings

Transcription

1 Hydrothermal regime of selected glaciers in S Spitsbergen derived from radio echo-soundings Mariusz Grabiec, Jacek Jania (Faculty of Earth Sciences University of Silesia) Dariusz Puczko (Institute of Geophysics, Polish Academy of Sciences) Grzegorz Gajek (Institute of Earth Science, Maria Curie-Sklodowska University) Sopot, 4-54 November 29

2 Objectives Determination of recent hydrothermal state of glaciers of southern Spitsbergen Indication of the direction of evolution of hydrothermal regime under changing climatic conditions Estimation of water content within polythermal glaciers

3 Schematic view of different polythermal structures (Pettersson, 24) Structure typical for most Svalbard glaciers Grey temperate ice

4 What is affecting variability of polythermal structure of glaciers in space and time? the surface energy balance net ablation at the surface liquid water content velocity field of the glacier (Blatter and Hutter, 1991) Pettersson, 24

5 How do we recognize the thermal structure of glaciers? Temperature measurements in vertical profiles Water level observations in explorated ice caves, moulins and englacial channels Radio echo-sounding survey Frontal part of Renardbreen Cold ice Temperate ice Spring MHz

6 Kinnvika Station Renardbreen Ny Aalesund SVALBARD Longyearbyen Werenskioldbreen Spitsbergen Polish Polar Station HORNSUND 12 July 22 Terra/MODIS NASA Ariebreen Hansbreen

7 Methods: Reflection profiling Equipment: Mala Geoscience RAMAC GPR CUII 25 MHz unshielded antennas GPS Leica 12 System Differential kinematic mode Fot. J. Jania

8 GPR tracks (UTM WGS84) Werenskioldbreen (DEM 199 L. Kolondra) Hansbreen DEM 25 Elevation [m a.s.l.] Renardbreen (km) Elevation (m a.s.l.) [km] (km)

9 Ariebreen 2 MHz autumn 27 Ariebreen - longitudinal profile elevation [m a.s.l.] distance [m] surface bedrock cold ice interface

10 NW 1997 Werenskioldbreen SE Pälli at al Werenskioldbreen - longitudinal profile (km) Elevation (m a.s.l.) NW SE 28 SE NW elevation (m a.s.l.) MHz - spring 28 distance (m) -1 cold ice bedrock topography

11 869 Renardbreen Renardbreen - longitudinal profile NW (km) SE elevation (m a.s.l.) distance (m) cold ice bedrock surface topography

12 Hansbreen 8562 S 1989 N Elevation [m a.s.l.] Glazovski et al [km] S N 25 MHz spring 28

13 Pälli at al Elevation [m a.s.l.] [km] 28 Hansbreen - longitudinal profile 6 5 S N 4 elevation [m a.s.l.] distance [m] surface bedrock cold ice interface

14 1997 Bedrock topography Pälli at al S Hansbreen - longitudinal profile N 4 elevation [m a.s.l.] distance [m] surface bedrock cold ice interface

15 Hansbreen ice thickness (m) [km] Total ice thickness Cold ice thickness cold ice thickness (m) [km] Elevation [m a.s.l.] Bedrock topography Lack of data [km]

16 Hansbreen Cold ice layer thickness 28 Winter accumulation (1989) cold ice thickness (m) winter accumulation [mm w.e.] [km] Grabiec et al. 26

17 Water content estimation from radio-wave velocity Common mid-point (CMP) 8554 Direct air wave Reflection from cold-temperate transition surface Travel time to diffractors Reflection from bed of glacier

18 Water content estimation from radio-wave velocity Absolute water content (W) % Looyenga (1965) formula W ε ' = ε ' 1 3 s 1 3 w ε ' ε ' 1 3 i 1 3 i Paren (197) formula W = 3 c V i 2 ε ' w ε ' i 8554 ε i, ε s, ε w - dielectric permittivity of pure ice, investigated ice and water c speed of light in the vacum V i radio wave-velocity in investigated ice

19 Experiment of temporal variability of polythermal structure Repeated profiles along the same track Spring 27, autumn 27, spring 28, autumn distance [m] W W Cold ice E E thickness [m] Temperate ice 3 35 cold ice 28 bed 28 bed spring 27 cold ice spring 27 bed autumn 27 cold ice autumn 27 bed 29 cold ice autumn 29

20 Conclusions Stages of thermal evolution of the glaciers 1 Hansbreen - longitudinal profile elevation [m a.s.l.] Renardbreen - longitudinal profile distance [m] surface bedrock cold ice interface 4 elevation (m a.s.l.) Werenskioldbreen - longitudinal profile -1 5 distance (m) cold ice bedrock surface topography Ariebreen - longitudinal profile elevation (m a.s.l.) elevation [m a.s.l.] distance (m) cold ice bedrock topography distance [m] surface bedrock cold ice interface

21 Conclusions Spatial distribution of cold ice layer is very complex. Cold ice layer forms porous structure filled by temperate ice in zones of moulins and/or crevasses Temporal variability of thermal structure from season to season is governed by dynamics, supraglacial/englacial drainage system and winter cooling Water content within temperate ice was estimated on.9 7,6% (according to different estimation methods), whereas liquid water formed <.9% of cold ice layer.

22 Thank you!

23 References: - Blatter, H., and K. Hutter 1991: Polythermal conditions in arctic glaciers, J. Glaciol., 37 (126), Glazovsky A.F., Kolondra L., Moskalevsky M.Yu. Jania J. 1992: Research into the Hansbreen, a tidewater glacier in Spitsbergen. Polar Geogr. Geol., 16(3), Glazovsky A.F., Macheret Yu.Ya., Moskalevsky M.Yu. 1991: Tidewater glaciers of Spitsbergen, Glaciers-Ocean- Atmosphere Interactions (Proceedings of the International Symposiumheld at St Petersburg, September 199). IAHS Publ. no. 28, Grabiec M., Leszkiewicz, J., Głowacki P., Jania J., 26: Distribution of snow accumulation on some glaciers of Svalbard. Polish Polar Research, 27(4), s Jania J., Mochnacki D., Gądek B. 1996: The thermal structure of Hansbreen, a tidewater glacier in southern Spitsbergen, Svalbard. Polar Res. 15(1), Jania J., Pulina M. 199: Field investigations performed during the glaciological Spitsbergen expedition in 1989: interim report. Katowice, Poland. University of Silesia. Faculty of Earth Sciences, Department of Geomorphology - Jania J., Macheret Yu.Ya., Navarro F.J., Glazovsky A.F., Vasilenko E.V., Lapazaran J., Glowacki P., Migala K., Balut A., Piwowar B.A. 25: Temporal changes in the radiophysical properties of a polythermal glacier in Spitsbergen. Ann. Glaciol. 4, Macheret Yu.Ya., Moskalevsky M.Yu., Vasilenko E.V. 1993: Velocity of radio waves in glaciers as an indicator of their hydrothermal state, structure and regime. J. Glaciol., 39 (132), Moore J.C., Pälli A., Ludwig F., Blatter H., Jania J., Gadek B., Glowacki P., Mochnacki D., Isaksson E. 1999: High resolution hydrothermal structure of Hansbreen, Spitsbergen, mapped by ground-penetrating radar. J. Glaciol., 45 (151), Pälli A., Moore J.C., Jania J., Kolondra L., Glowacki P. 23: The drainage pattern of Hansbreen and Werenskioldbreen, two polythermal glaciers in Svalbard. Polar Res. 22(2), Pettersson R. 24: Dynamics of the cold surface layer of polythermal Storglaciären, Sweden, Doctoral dissertation, Department of Physical Geography and Quaternary Geology,Stockholm University, 32 pp. - Řehak J. Ouhrabka J., Braun J. 199: New information about the interior drainage of subpolar glaciers and the structure of medial moraines of the southwest Spitsbergen. Stud. Carstologica 1, Schroeder J. 1995: Les moulins du glacier Hans de 1988 à In Griselin M., ed. Actes et 3e Symposium International Cavités Glaciaires et Cryokarst en Régions Polaires et de Haute Montagne, 1-6 novembre 1994, Chamonix, France. Paris, Les Belles Lettres, (Annales Littéraires de l Université Besançon 561, Série Géographie 34.)