Modeling of Mountain Permafrost Distribution in the Semi-arid Chilean Andes

Transcription

1 Modeling of Mountain Permafrost Distribution in the Semi-arid Chilean Andes Guillermo Azócar Sandoval Atacama Ambiente Consultores December 05, 2018 Ice in the Atacama Desert, Centro UC Desierto de Atacama, PUC

2 Outline I. Introduction II. Study area III. Methods for mapping permafrost distribution IV. Results V. Discussion VI. Conclusion VII. Future Challenges VIII. Work in Progress

3 1. INTRODUCTION I. What is Permafrost? What is Permafrost? Permafrost, is a rock or sediment whose temperature remains below 0 C for two or more consecutive years (Davis, 2000) Where does Permafrost Exist? It is zonal phenomenon: Polar regions and highland zones around world (Plateaus, highest mountain ranges) What is Mountain Permafrost? Mountain permafrost is the presence of frozen ground in mountain areas.

4 1. INTRODUCTION I. What is permafrost? II. Where Does Permafrost Exists? III. What is Mountain Permafrost? IV. What Factor Control Permafrost Distribution? What Factors Control Mountain Permafrost Distribution? Mountain permafrost and its extreme spatial variability is dominated by three different environmental factors at difference scales (Gruber & Haeberli, 2009): Global-scale Meso-scale Micro-scale Climate Topography Ground Conditions Latitude Global circulation Slope Exposure Altitude Material and surface cover types

5 1. INTRODUCTION I. What is permafrost? II. Where Does Permafrost Exists? III. What is Mountain Permafrost? IV. What Factor Control Permafrost Distribution? Rock glaciers are common indicators of past and present permafrost conditions in mountain areas ROCK GLACIER Active rock glacier El Paso located in the eastern side of the semi-arid Andes near the Aguas Negras border crossing between Argentina and Chile (30.2 S, 69.8 W; photographed by the author, December 12, 2009

6 1. INTRODUCTION I. What is permafrost? II. Where Does Permafrost Exists? III. What is Mountain Permafrost? IV. What Factor Control Permafrost Distribution? V. What is Rock Glacier? Active rock glacier Inactive rock glacier Relict rock glacier

7 1. INTRODUCTION I. What is permafrost? II. Where Does Permafrost Exists? III. What is Mountain Permafrost? IV. What Factor Control Permafrost Distribution? V. What is Rock Glacier? VI. Permafrost modelling Review of Permafrost Modelling

8 1. INTRODUCTION I. What is permafrost? II. Where Does Permafrost Exists? III. What is Mountain Permafrost? IV. What Factor Control Permafrost Distribution? V. What is Rock Glacier? VI. Permafrost Modelling VII. Why is important to study permafrost distribution in the Andes? Why study permafrost distribution in the semi-arid Chilean Andes? Increasing pressure of mining activities in high mountain areas (Brenning & Azócar, 2010) Concerns about the consequences of climate change in permafrost areas in term of slope stability and hydrological systems Current permafrost distribution is practically unknown for the Andes

9 1. INTRODUCTION I. What is permafrost? II. Where Does Permafrost Exists? III. What is Mountain Permafrost? IV. What Factor Control Permafrost Distribution? V. What is Rock Glacier? VI. Permafrost Modelling VII. Why is important to study permafrost distribution in the Andes? Permafrost Distribution Modelling in the semi-arid Chilean Andes Goal: To create an index map of potential permafrost distribution in the semi-arid Chilean Andes between ~29 and 32 S based on statistical modelling of topographic and climatic conditions and rock glacier activity status. Azócar, G. F., Brenning, A., and Bodin, X.: Permafrost distribution modelling in the semi-arid Chilean Andes, The Cryosphere, 11, , 2017.

10 2. STUDY AREA I. Location Location facts Andes mountain (~29-32 S) Longitudinal distance (~ 400 km) Semi-arid region Four watersheds Population is scarce Population relies on water resources from the mountain

11 2. STUDY AREA I. Location II. Periglacial and Glacial Environment Glaciers are rare in the semi-arid Chilean Andes but rock glaciers are abundant (In: : Azócar & Brenning, 2010 :Author photo album)

12 3. METHODS Methods: For Modelling Mountain Permafrost in the semi-arid Chilean Andes

13 3. METHODS I. Rock Glacier Inventory a. Mapping Methods Methods: Inventory of Rock Glaciers Purpose: Create a variable indicative of permafrost conditions The inventory was prepared using Bing Maps Aerial imagery Each rock glacier mapped as point mark at the end of the rock glacier front Rock glaciers according its dynamic states were identified and categorized as active, inactive, intact and relict forms Attributes related to location, altitude and PISR were calculated

14 4. RESULTS I. Rock Glacier Inventory Results: Rock Glacier Inventory 3575 rock glaciers were complied based on existing inventories and the identification of additional rock glaciers in the study area 1075 Active rock gl. 493 Inactive rock gl. 343 Intact rock gl Relict rock gl. 14

15 4. RESULTS I. Rock Glacier Inventory II. MAAT Results: Statistical Temperature Model The 0 C MAAT isotherm is located at ~4250 m a.s.l. in the northern (29 S) section and drops altitudinally to 4000 m a.s.l. in southern section (32 S) of the study area. Area de Estudio 15

16 4. RESULTS I. Rock Glacier Inventory II. MAAT III. Permafrost Ocurrence Model PPS 0.5 (6.8%=2636 km 2 ) PPS 0.75 (2.7%= 1051 km 2 ) Lower PPSs (<0.5) are associated with lower hill slopes and valley bottoms Large spatial permafrost extension: Huasco and Elqui watersheds Potential permafrost areas tend to decrease to the South Where elevation rises considerably, permafrost tends to be concentrated Indices of predictive efficiency Permafrost distribution model Based on training set derived from the spatial cross-validation (median value) Overall Accuracy 0.66 Misclassification error rate 0.34 Sensitivity 0.60 Specificity 0.73 Non-spatial cross validation AUROC (median) - Spatial cross validation AUROC (median) -

17 4. RESULTS I. Rock Glacier Inventory II. MAAT III. Permafrost Ocurrence Model 18

18 5. DISCUSSION I. Distribution of Rock Glacier and MAAT II. Statistical Temperature Model Results III. Interpretation of Score of IV. Permafrost Occurrence Comparison of Permafrost Prediction Models V. Permafrost Area and Effects of Climate Changes Discussion Rock glaciers along the study area are abundant, with an important presence of active (n=1075), inactive (n=493), intact (n=343) and relict rock glaciers (n=1664). A significative number of rock glaciers (~60-80%) is located in positive MAAT levels. Probably, local topographic factors and delayed response of rock glaciers can contribute to the occurrence of rock glaciers in unfavorable temperature conditions. The occurrence of permafrost in the semi-arid Chilean Andes between 29 and 32 S. is relative continuous above ~4500 m a.s.l. and discontinuous between ~3900 to 4500 m a.s.l.

19 5. DISCUSSION I. Distribution of Rock Glacier and MAAT II. Statistical Temperature Model Results III. Interpretation of Score of IV. Permafrost Occurrence Comparison of Permafrost Prediction Models V. Permafrost Area and Effects of Climate Changes Discussion Permafrost areas near the lower boundary of permafrost distribution are more sensitive to degradation processes due to possible effect of climate changes (Haeberli, 1992). A rise in air temperature can potentially lead to thaw ice rich frozen ground (i.e., intact rock glacier). In addition, this warming could lead to geotechnical problems related to high-altitude infrastructure build by mining companies or in connection with public infrastructures (i.e., border roads, tunnels). Moreover, an increase in the numbers of debris flow and rock fall activity would take place (Haeberli, 1992; Zimmermann & Haeberli, 1992).

20 5. DISCUSSION I. Distribution of Rock Glacier and MAAT II. Statistical Temperature Model Results III. Interpretation of Score of IV. Permafrost Occurrence Comparison of Permafrost Prediction Models V. Permafrost Area and Effects of Climate Changes Discussion Areas with PPS 0.75, permafrost will occur in almost all environmental conditions. Areas where PPS ranges between 0.5 and 0.75, permafrost will be present only in the favorable cold zones describe before. In areas with PPS < 0.5, permafrost may be present in exceptional environmental circumstances.

21 5. DISCUSSION I. Distribution of Rock Glacier and MAAT II. Statistical Temperature Model Results III. Interpretation of Score of IV. Permafrost Occurrence Comparison of Permafrost Prediction Models V. Permafrost Area and Effects of Climate Changes Comparison with PZI, Gruber, 2012 PPS mean = 0.53 PZI mean = 0.18 Areas with PPS 0.75 PPS = (1284 km 2 ) PZI = (209 km 2 ) Permafrost Probability Score from this study Permafrost Probability Score from this study resampling to 1 km Global Permafrost Zonation Index model (PZI; Gruber, 2012)

22 6. CONCLUSION Conclusions The statistical permafrost distribution model proposed have enables more detailed calculation as well as the inclusion of low-altitude permafrost in contrast to the global permafrost estimation model for the semi-arid Chilean Andes. The overall permafrost distribution within the study area is controlled by climate and topographic factors. However, local environmental factors (e.g., substrate properties) not included in the model, could determine permafrost presence locally. GAM has shown to be a reliable statistical method for modeling permafrost distribution for large mountain regions. The permafrost model was build based on indirect evidence of permafrost presence. In order to overcome this limitation, an inventory of empirical evidence of permafrost through field observations is highly recommended to improve the input data quality as well as to validate the model results.

23 Future Challenges More complete inventories of rock glacier forms along to the Andes including relict forms. Temperature records are scarce in the Andes Mountain. The influence of the precipitation. Ground control site for validation of model. Physically models.

24 Work in Progress Permafrost distribution modelling in the Maipo River Watershed, Chile. Contributors: - Pedro Straub, Geographer student from PUC. - Guillermo Azócar Sandoval, Atacama Ambiente Consultores. - Dr. Juan Luis Garcia, Instituto de Geografía UC Azócar, G. F., Brenning, A., and Bodin, X.: Permafrost distribution modelling in the semi-arid Chilean Andes, The Cryosphere, 11, , ,

25 Work in Progress Permafrost distribution modelling in the Maipo River Watershed, Chile. Contributors: - Pedro Straub, Geographer student from PUC. - Guillermo Azócar Sandoval, Atacama Ambiente Consultores. - Dr. Juan Luis Garcia, Instituto de Geografía UC Azócar, G. F., Brenning, A., and Bodin, X.: Permafrost distribution modelling in the semi-arid Chilean Andes, The Cryosphere, 11, , ,

26 Bibliografía Azócar, G. F., Brenning, A., and Bodin, X.: Permafrost distribution modelling in the semi-arid Chilean Andes, The Cryosphere, 11, , Azócar, G., & Brenning, A. (2010). Hydrological and geomorphological significance of rock glaciers in the dry Andes, Chile (27-33 S). Permafrost and Periglacial Processes, 21(1), Barry, R. G. (1992). Mountain weather and climate. New York, USA: Routledge. Brenning, A. (2005a). Climatic and geomorphological controls of rock glacier in the Andes of central of Chile. Doctoral thesis, Humboldt-Universität, Mathematisch-Naturwissenschaftliche Fakultät II, Berlin, Germany. Brenning, A., & Azócar, G. (2010b). Minería y glaciares rocosos: impactos ambientales, antecedentes políticos y legales, y perspectivas futuras. Revista de Geografía Norte Grande, 47, Brenning, A., & Trombotto, D. (2006). Logistic regression modeling of rock glacier and glacier distribution: Topographic and climatic controls in the semi-arid Andes. Geomorphology, 81, Gruber, S. (2012). Derivation and analysis of a high-resolution estimate of global permafrost zonation. The Cryosphere, 6(1), doi: /tc Gruber, S., & Haeberli, W. (2009). Mountain permafrost. In R. Margesin (Ed.), Permafrost Soils (pp ). Berlin: Springer- Verlag. Hiebl, J., Auer, I., Böhm, R., Schöner, W., Maugeri, M., Lentini, G.,... Müller-Westermeier. (2009). A high-resolution monthly temperature climatology for the greater Alpine region. Meteorologische Zeitschrift, 18(5), Hoelzle, M., & Haeberli, W. (1995). Simulating the effects of mean annual air temperature changes on permafrost distribution and glacier size: An example from the Upper Engadin, Swiss Alps. Annals of Glaciology, 21, Unidad de Gestión de Proyectos del Instituto de Geografía de la Pontificia Universidad Católica de Chile [UGP UC]. (2010). Dinámica de glaciares rocosos. Dirección General de Aguas, Unidad de Glaciología y Nieves. Santiago: Ministerio de Obras Públicas. Nicholson, L., Marín, J., López, D., Rabatel, A., Bown, F., & Rivera, A. (2009). Glacier inventary of the upper Huasco valley, Norte Chico, Chile: Glacier characteristics, glacier change and comparison with central Chile. Annals of Glaciology, 50(53), Van Everdingen, R. (Ed.). (1998). Multi-language glossary of permafrost and related ground-ice terms. Calgary, Alberta, Canada: International Permafrost Association. 27

27 Thanks!