Schedule: Study year 2012/13. Introduction Impact of glaciers on runoff Methods. - Conceptualisation of Ice Melt - Index based melt method

Transcription

1 Klima und hydrologische Prozesse Possible Impacts of Climate Change on Water Resources Schedule: Study year 2012/13 Wahlfachkatalog A: Gewässerkunde und Hydrologie (Dipl.Stud.) bzw. Modul Hydrologie und wawi. Planung (Mag.Stud.) Vorl. Nr Schulz, Holzmann (IWHW-BOKU): Summary of course, National Geographics movie presentation on global glacier retreat, Discussion Content Introduction Impact of glaciers on runoff Methods - Conceptualisation of Ice Melt - Index based melt method Test Basins and Monitoring Results Conclusions and remarks

2 Introduction Glacial ice can range in age from several hundred to several hundreds of thousands years, making it valuable for climate research. Because glaciers are so sensitive to temperature fluctuations accompanying climate change, direct glacier observation may help answer these cc-related questions. Since the early twentieth century, with few exceptions, glaciers around the world have been retreating at unprecedented rates. The prevailing class unit focuses on mountaineous glacier melt processes only and does not directly address polar and continental glaciers issues. Interesting Link: NSIDC National Snow and ice data center: Glacier system Glaciers are made up of fallen snow that, over many years, compresses into large, thickened ice masses. Glaciers form when snow remains in one location long enough to transform into ice. What makes glaciers unique is their ability to move. Due to sheer mass, glaciers flow like very slow rivers. Glaciers begin to form when snow remains in the same area yearround, where enough snow accumulates to transform into ice. Each year, new layers of snow bury and compress the previous layers. This compression forces the snow to re-crystallize, forming grains, causing the snow to slowly compact and increase in density. After about two winters, the snow turns into firn, an intermediate state between snow and glacier ice. The sheer weight of a thick layer of ice and the fact that it deforms as a "plastic" material, combined with gravity's influence, causes glaciers to flow very slowly. Glaciers periodically retreat or advance, depending on the amount of snow accumulation or ablation that occurs. This retreat or advance refers only to the position of the terminus, or snout, of the glacier. Even as it retreats, the glacier still deforms and moves downslope.

3 Glacier system (From Zemp et al, 2008a) Glacier domain After Schuler 2002:

4 Glacier retreat (From Gletscherbericht ÖAV, 2002) Glacier Melt

5 Glacier functions Impact of Glaciers on the environment: Source of freshwater balancing / compensation of river discharge (in summer) affect local climate stimulates tourism (ski resorts, landscape) hydropower production water temperature in rivers (fish and microfauna) Glaciers in hyd. models modelling of glaciers in runoff-models: How can glaciers be represented in runoff models? Which type of glacier melt and routing routines are necessary to capture the specific characteristics of glacial discharge?

6 Concepts Runoff concept for hillslopes Runoff Formation Runoff modeling concept Surface storage Diversion Soil storage Streamflow Ground water storage From

7 Concepts Runoff concept for glaciers Glacier melt concept Surface storage Time shift (delay) Linear storage Split Function Conceptual hydrol. Model

8 Melt modelling modelling of glaciers in runoff-models: Glacier ice melt only occurs on bare (non snow covered) ice Spatial and temporal evolution of snowmelt has to be considered (accumulation / depletion) Similar model concepts for snow and icemelt, but different parameterization (index based models) runoff formation is quicker for icemelt than for snowmelt Research Areas Pegel Kees (Obersulzbach) 22 km 2 Goldbergkees 3 km 2

9 Semi distributed (100-Meter elevation bands) Daily and hourly time resolution Snow and Ice Melt consideration Index Model approach (seasonal variable) Applied Melt Model - Temperature Index - Radiation Index M i, k, j TIk Tempi, j M i, j RI Radi, j - Mixed Index Where M i, k, j M Snowmelt Rate (mm) TI Temperature Index RI Radiation Index Temp Air Temperature Rad Global Radiation k seasonal Index i temporal Index j elevation index TIk Tempi, j where 1 RI Rad i Basin Goldbergkees Sonnblick Observatory Discharge

10 Results - Goldbergkees Discharge measurements from Koboltschnig (2007). Results - Goldbergkees Air Temperature Sonnblick - August 2003 Temperature oc Time (h) Global Radiation Sonnblick - August 2003 Radiation (W/m2) Time (h) Runoff Terminus - August 2003 Discharge (m3/s) Time (h)

11 Results - Goldbergkees Temperature Index Method - August 2003 Runoff (m3/s) Q observed TI 3.5 SNOW Q simulated TI ICE Time (h) Results - Goldbergkees Radiation Index Method - August 2003 Runoff (m3/s) Q observed RI SNOW 0.1 Q simulated RI ICE Time (h)

12 Results - Goldbergkees Mixed Index Method - August 2003 Runoff (m3/s) Q observed 0.5 Q simulated Time (h) Results - Goldbergkees Mixed Index Method / Linear Storage - August 2003 Runoff (m3/s) Q observed Q simulated Time (h)

13 Ice Melt Ice melt contribution to total runoff Goldberg glacier total runoff icemelt runoff Q(m 3 s -1 ) Apr May Jun Jul Aug Sept-03 From Koboltschnig (2007) Basin Kees Discharge Gauge Kees Discharge Gauge Sulzau

14 Results - Kees Mixed Index Method / Linear Storage - August 2003 Runoff (m3/s) TI 0.5 Q SNOW 3.5 RI SNOW 0.05 observed TI ICE 6.0 RI Q ICE simulated Time (h) Glacier melt concept Time shift (delay) Linear storage Split Function Conceptual hydrol. Model

15 Results - Kees Melt period 2003 spec. Discharge (mm/h) Q observed Qbaseflow simulated Qdirectmelt simulate Direct Melt SNOW = 25% Direct Melt ICE = 50% d Time (h) Water Balance Model - August 2003 Results - Kees spec. Discharge (mm/h) Q observed Qbaseflow simulated Qdirectmelt simulate d Time (h)

16 Conclusions A total retreat of the Austrian glaciers below 3000 m can be expected by the end of this century. Nowadays glacier melt significantly contributes to alpine headwater discharge. A lack of melt water will lead to extreme low flows for alpine basins during summer. Negative glacier mass balance is caused by increasing temperatures and decreasing snow accumulation during late winter periode. Snow and glacier melt processes can be reliably simulated by hydrological models. Index based melt models perform reasonable. Mixed index approach performs best with respect to diurnal variation. Different melt indices are applied for snow and ice. Process knowledge from experts enables a modular application of model components reflecting the specific processes of a particular glacier. Collaboration between hydrologists and glaciologists is recommendable! Klima und hydrologische Prozesse Possible Impacts of Climate Change on Water Resources Schedule: Study year 2012/13 Wahlfachkatalog A: Gewässerkunde und Hydrologie (Dipl.Stud.) bzw. Modul Hydrologie und wawi. Planung (Mag.Stud.) Vorl. Nr Schulz, Holzmann (IWHW-BOKU): Summary of course, National Geographics movie presentation on global glacier retreat, Discussion

17 Mass Balance Monitoring of glacier mass balance Research Project SNOWTRANS Transformation of observed and computed iceand snowmelt data to ungauged basins HYDROLOGIE ÖSTERREICHS (HÖ 29) Beitrag Österreichs zum INTERNATIONAL HYDROLOGICAL PROGRAMME (IHP) Project Leadership: H. Holzmann (BOKU), W. Schöner (ZAMG) Glacier Workshop Obergurgl, Aug. 2007

18 Monitoring of depletion pattern Comparison with depletion patterns based on: Digitized Ortophotos (e.g. 1998) LANDSAT images N Subpixel Analysis of MODIS images Field mapping Kilometers Amateur photos depletion 1998 Snow depth observations Avalanche probe Basin Goldbergkees

19 Snow depth observations MODIS Szene Wien, ÖAW 17. Nov. 2003

20 Monitoring of icemelt Ablation sticks drilled into the ice by steam drill. (Heuke Ice Drill) Positioning by GPS Ablation observations every 2-3 weeks Total ablation estimated by spatial interpolation Benefit: direct mass balance estimation, calibration of hydrological model Monitoring of runoff Automatic Runoff Gauge (bubble pressure system) Flow measurements (velocimeter) Seasonal rating curve

21 Mass Balance Mass balance estimation Mass Balance

22 Mass Balance Surface energy balance The balance of all energy fluxes from or towards a glacier surface of unit area is given by QN + QH + QL + QG + QR + QM = 0 where QN is the net radiation, QH is the sensible heat flux, QL is the latent heat flux related to phase changes, QG is the heat exchange with the ground, QR is the heat flux supplied by rain and QM is the flux of latent energy available for melt. By convention, energy fluxes directed towards the surface are denoted by a positive sign while those away from the surface carry a negative sign. Glacier retreat Climate change and Glacier retreat

23 Research Projects (From Zemp et al, 2005) Research Projects (From Zemp et al, 2008b)

24 Glacier inventory Data source: Digital Orthophoto Glacier inventory Bright blue: glacier areas 1995 (Corine) Red: glacier areas 2003 (orthofoto)

25 Glacier retreat Subbasin glacier area 1995 (km2) glacier area 1995 (%) gl. area 2003 gl area 2003(%) reduction in % E inzugsgebiet Bezeichnung EG_ID vergletscherte Fläche Hydris2 F lächenanteil Gletscher Hydris2 G letscherbestand 2003 Flächenanteil 2003 Abnahme in % Krimmler Ache 2 14,26 12,98% 8,14 7,41% 42,93% S ulzau 4 20,29 25,08% 15,21 18,80% 25,05% Neukirchen 5 8,12 20,02% 5,47 13,49% 32,60% Habach 6 4,85 10,62% 3,09 6,76% 36,30% Hollersbach 9 2,11 3,11% 0,94 1,38% 55,60% Bachfassung Amertaler S ee 11 0,31 14,27% 0,14 6,65% 53,41% Bachfassung Ödbach 12 1,10 23,28% 0,56 11,79% 49,34% S peicher KW Uttendorf 13 5,82 15,18% 5,81 15,15% 0,22% Uttendorf S tubache 14 1,20 1,44% 0,84 1,01% 30,09% Bachfassung Käferbaeche 18 5,46 62,11% 3,76 42,72% 31,22% Bachfassung Hirtzbach 20 0,65 8,82% 0,22 3,04% 65,59% Mooserboden u. Wasserfallboden 21 10,79 25,84% 8,81 21,10% 18,35% Kaprun 22 1,80 3,81% 1,24 2,64% 30,68% Bruck Fuscher Ache 26 7,74 5,29% 4,68 3,20% 39,57% Bachfassung Huettwinkelache+L enzangerbach 28 3,68 16,24% 2,75 12,14% 25,28% R auris 29 3,27 1,49% 1,57 0,72% 52,11% Tagesspeicher Nassfeld 31 2,69 7,10% 0,97 2,56% 63,94% Bad Hofgastein 33 3,38 1,88% 1,63 0,91% 51,85% Großarl 37 0,81 0,47% 0,08 0,04% 90,55% Tenneck 49 2,71 3,79% 0,00 0,00% 100,00% S umme 98,33 65,89 32,99% Glacier Research (From Zemp et al, 2008a)

26 Research (From Zemp et al, 2008a) Glacier Monitoring (From Kuhn, 2008)

27 Glacier Monitoring (From Kuhn, 2008) Runoff Analysis: Pegel Obersulzbach - Aug Glacier Monitoring Abfluss (m3/s) Q beobachtet observed Q Cosero model without glacier Q Cosero model with + Gletscher glacier Glacier area Stunden

28 Runoff 2003 (area 1987) Pegel Obersulzbach - Aug Abfluss (m3/s) Q beobachtet observed Q Cosero model without glacier Q Cosero model with + Gletscher glacier Glacier area Stunden Conclusions A total retreat of the Austrian glaciers below 3000 m can be expected by the end of this century. Nowadays glacier melt significantly contributes to alpine headwater discharge. A lack of melt water will lead to extreme low flows for alpine basins during summer. Negative glacier mass balance is caused by increasing temperatures and decreasing snow accumulation during late winter periode. Snow and glacier melt processes can be reliably simulated by hydrological models. Index based melt models perform reasonable. Mixed index approach performs best with respect to diurnal variation. Different melt indices are applied for snow and ice. Process knowledge from experts enables a modular application of model components reflecting the specific processes of a particular glacier. Collaboration between hydrologists and glaciologists is recommendable!

29 Outcomes of Unit You should be able to answer the following questions: How old can the ice masses of global glaciers be? How can the spatial domain of an alpine glacier be classified? Which components are relevant for the glacier mass balance? What are the meteorological driving forces of glacier melt and how can melt be computed? Decribe the terms accumulation area, ablation area, equilibrium line and terminus with respect to glacier? How are snowmelt and glacier icemelt interrelated? Which process dominates in which month? How can snow cover patterns be monitored? What is the temperature index method? What is the radiation index method? What are the expected consequences of glacier retreat for the environment? References Zemp, M., Paul, F., Hoelzle, M. & Haeberli, W. (2008a): Glacier fluctuations in the European Alps : an overview and spatio-temporal analysis of available data. In: Orlove, B., Wiegandt, E. & B. Luckman (eds.): The darkening peaks: Glacial retreat in scientific and social context. University of California Press. Zemp, M., Frauenfelder, R., Haeberli, W. & Hoelzle, M. (2005): Worldwide glacier mass balance measurements: general rends and first results of the extraordinary year 2003 in Central Europe. Data of Glaciological Studies, 99: p Zemp, M., Haeberli, W., Hoelzle, M. & Paul, F. (2008b): Alpine glaciers to disappear within decades? Geophysical Research Letter. Haeberli, W. (1995): Glacier fluctuations and climate change detection operational elements of a worldwide monitoring strategy. WMO Bulletin, 44: p Hock, R. (1999): Distributed temperature-index ice- and snowmelt model including potential direct solar radiation. J. Glaciol., 45, Koboltschnig G. (2007): Multivalidation approach of hydrological snow and ice melt models in high alpine, glaciated catchments. Doctoral thesis at the BOKU university, Vienna. Kuhn M. (2008): Klimawandel und Gletscherschwund. In Auswirkungen des Klimawandels auf die österreichische Wasserwirtschaft. Broschüre des Lebensministeriums.