Sea to Summit Patagonia
Chile
A comparative study on surge-type glaciers and glacial lake outburst floods. Brief Project Proposal
Summary
The glaciers of Patagonia are some of the most temperate, fastest, and most erosive glaciers on Earth and Pio XI Glacier makes no exception. In contrast to the general trend for glaciers of the Southern Patagonia Icefield (Figure 1, Top), this calving glacier has experienced a large cumulative frontal advance since 1945, which led to the damming of Lake Greve. To date, a conclusive explanation for the behaviour of Glacier Pio XI (Figure 1, Bottom) remains to be found.
In an effort to better understand this anomalous advancing behaviour, the potential link to climate change and the implications for hazard generation, the Sea to Summit Patagonia Project (SSPP) will venture into the interior of the Patagonian Southern Ice Field to:
a) Bring new insights pertaining to the underlying factors that determine the transport of mass down-glacier and the fluctuations of frontal positions of Pio XI Glacier;
b) Assess the present risk of glacial lake outburst floods at Lake Greve.
Central to this are the following secondary objectives:
Assess the spatial characteristics (and changes) of Pio XI Glacier such as the supraglacial hydrology, and surface topography.
This will involve an aerial photogrammetric survey (via a drone DJI Mavic or Wingtra) to map the geometry and hypsometry of the glacier as well as georeferencing activities to map and geotag the position of the snout of the glacier. Furthermore, repeat photography will be employed to qualitatively assess the frontal geometric changes since the last field visit.
The output from this work will be a digital terrain model (orthomosaic) that can be used to assess the complex interaction between ice dynamics, ice calving and mass-balance components (among others).
Measure the surface ice flow velocity[1] of Pio XI glacier to confirm whether it is surge type glacier or not.
This will be achieved using a Global Navigation Satellite System (GNSS) Real Time Kinematic Survey as employed during the Karakoram Anomaly Project in Pakistan in 2015.
Measure the geometry of the Pio Xi ice dam at Lake Greve to determine the risk of catastrophic flooding.
This will be achieved using a second terrestrial photogrammetric survey, and geomorphic mapping techniques as explained in McKillop and Clague (2000); Huggel, (2004); Carter (2007).
The Sea to Summit Patagonia Project along with the Karakoram Anomaly Project is part of an ongoing global initiative to improve understanding pertaining to climate change impacts and hazardous glacial phenomena in high topography and mid-high latitude environments.
Knowledge of ice velocity is essential to identify areas of rapid ice discharge, define the origin of ice and the limits of glacier catchments, calculate ice discharge into lakes or the ocean, and compare the results with surface mass balance to estimate the icefield mass balance, or study ice flow dynamics in relation to climate change. Until recently, only partial coverage of ice motion of the Patagonian Icefields has been available [Naruse et al., 1992; Michel and Rignot, 1999; Skvarca et al., 2003; Rivera et al., 2007; Stuefer et al., 2007; Ciappa et al., 2010; Sugiyama et al., 2011; Rivera et al., 2012a; Willis et al., 2012a; Muto and Furuya, 2013; Sakakibara et al., 2013; Sakakibara and Sugiyama, 2014].
Project Description
Logistical Plan
Due to the remoteness of the field site, the SSPP team will embark on a scientific voyage (Figure 2) crossing varying terrain such as sea and land and combining different means of locomotion such as boat, foot and skis, testing physical endurance, tolerance to adversity, navigation in difficult terrain and problem-solving skills. The expedition will be a first in the area in terms of scope and if successful, it will bring important insights about glacioclimatic interactions, calving dynamics, Holocene climate change and the role of topography in controlling glacier behaviour.
In terms of logistics, the plan will be as follows: 1) domestic flight to Puerto Montt followed by a 2) ferry ride to Puerto Eden and then 3) a boat hire to Pio XI Glacier (red lines). Next, the team will ski across the icefield (blue line) until O’Higgins lake where they will take a boat to O’Higgins settlement (red line). The last leg of the journey will be a vehicle/bus drive back to Puerto Montt (yellow line). We have a contingency logistical plan which comprises access to the icefield via Coyhaique instead of Puerto Montt.
Project Opportunity and Innovation
The need for a conclusive explanation for the behaviour of Glacier Pio XI
Remarkably little is known about the Patagonian icefields. They remain "amongst the least known of the world's glaciers" (Grove, 1988:263), despite the fact that the South Patagonian Icefield is one of the major ice masses of the world. The tantalising fragments of information that do exist suggest that there is a rich glaciological source to be mined in Patagonia yielding insights into glacioclimatic interactions, calving dynamics, Holocene climate change and the role of topography in controlling glacier behaviour (Warren and Sugden, 1993).
The Patagonian icefields are the largest mid-latitude ice masses and yet few glaciological data exist for them. Neither full mass-balance studies nor empirical or numerical modelling investigations of glacier dynamics have yet been published. The presence of the Andes lying athwart the westerlies makes for a dynamic glacial system with steep balance gradients and west- east equilibrium-line altitude gradients. The overall trend during the 20th century has been glacier retreat. However, whereas most eastern outlets retreated consistently from the beginning of the century, recession on the west began later, has been interrupted by readvances, and most recently has accelerated markedly, reaching higher mean rates of retreat than those on the east (Rivera et al., 1997, Rivera and Cassasa, 1999).
This contrast may result from a predominantly precipitation-controlled mass-balance regime in the west and a dominant temperature control in the east. Superimposed on these contrasts is the anomalous behaviour of certain calving glaciers, the oscillations of which contrast in magnitude and timing with each other and with non-calving glaciers, and which in many cases do not relate directly to climate change (Wilson et al., 2016). Two large calving outlets are at or near their Neoglacial maxima. One of them, Pio XI, (48.26°S, 73.68°W; 1234 km2)1, the largest outlet glacier of the Southern Patagonian Icefield (12 363 km2from 48.5°S to 51.5°S), has experienced a large cumulative frontal advance since 1945 (Figure 3 and 4). To date, a conclusive explanation for the behaviour of Glacier Pio XI remains to be found (ibid).
Citing the large frontal fluctuations and the periodic occurrence of distinctive medial moraine folding, Rivera and others (1997), suggest the Glacier Pio XI is a surge-type glacier, however much uncertainty exits around the trigger mechanisms for this behaviour. Furthermore, Wilson et al., (2016), suggested that the transport of mass down-glacier and the fluctuations of frontal positions are influenced by a complex interaction between ice dynamics, ice calving and mass-balance components (among others). Differentiating between the mass balance and surge dynamic components of Glacier Pio XI’s behaviour remains difficult. This is because understanding of these two variables is limited by the lack of elevation data further up-glacier in the accumulation zones. Observations of ice thinning in these upper regions, would further confirm the influence of dynamically acquired thickening in lower regions. Further monitoring of these components, together with long-term acquisition of local climate data, is thus essential for the understanding of future behaviour.
This project will address these knowledge gaps in part as described above. We will link our field measurements to satellite derived velocities that are now possible (with the accessibility of imagery on high temporal resolution like Planet and Sentinel) and thus integrate new technological advances into very new field data. This in turn will enable us to upscale the field findings to the whole Pio XI area.
The need for monitoring of glacial lake outburst flood risk
With regard to possible hazards, the likelihood of future outburst events is highest in Southern Patagonia, which contains the largest number of moraine- and ice-dammed lakes (Figure 3, Wilson et al., 2018). It has been noted that if in a longer time period, the equilibrium line altitude of Pio Xi Glacier rises above a critical hypsometric threshold, accumulation area would change. This in turn would lead to thinning and the front of the glacier would start to retreat. When this happens, a sudden outburst flood of Greve Lake might occur. The possible retreat of the glacier and associated glacial flood of Greve Lake should be analysed in future investigations (Rivera and Casassa, 1999).
Continued glacial lake monitoring is recommended for the entire Patagonian Andes, particularly in light of the GLOF risks posed toward the future development in agriculture, tourism, hydropower and mining in these mountainous areas. This project will explore the likelihood of occurrence of GLOF at Lake Greve.
Predicting response to climate change
The Chilean and Argentinean Andes contain ~29,356 km2 of glacier ice (~93% of the total glacier area in South America) (RGI Consortium, 2017). Given ongoing climate change, the glaciers of the Patagonian icefields are important predictors of what we expect to occur in the coming decades in other glaciated, high-latitude regions, such as the Antarctic Peninsula and the Canadian Arctic, which are experiencing some of the most rapid warming on the planet.
To improve resilience of human life and assets to glacial hazards by advancing understanding of the mechanisms that have triggered GLOFs in Chile and Argentina
The Patagonian glacierised environments are increasingly being used for mining purposes, hydropower installations and for tourist activities, bringing people closer to glacial hazards (Dussaillant et al., 2010). Overall, Iribarren Anacona et al. (2015b) estimated that at least 31 glacial lakes have failed in Chile and Argentina since the eighteenth century, producing over 100 GLOF events. Importantly, this study notes that the number of GLOF events in Chile and Argentina has increased over the past three decades, highlighting the need for further investigation of the cryospheric, climatic and geomorphic processes driving this trend. Despite this situation, monitoring of glacial lake development and evolution in Chile and Argentina has been limited, with past investigations only covering relatively small regions of Patagonia (e.g. Loriaux and Casassa (2013), Iribarren Anacona et al. (2014) and Paul and Mölg (2014). Due to their sporadic nature, little is known about the specific mechanisms that have triggered GLOFs in Chile and Argentina.
Summary of observations from earlier studies and activities
Frontal fluctuations for Glacier Pio XI have been analysed by LLiboutry (1956, 1965), Mercer (1964), Iwata (1983), Aniya et. al (1992), Rivera (1992), Warren & Sugden (1993), Warren & Rivera (1994), Rivera et al., (1997a y b), Warren et al., (1997), Rivera & Casassa, (1999), Rivera et al., (2000) among others.
To summarise, between 1830 and 1928 the single snout of Pio XI advanced across the Greve Valley (where the northern and southern termini are located today) resulting in the formation of Lago Greve (Greve Lake) (Agostini, 1945). Following this advance, the glacier experienced a prolonged period of retreat up to 1945 (3–5 km), opening the Greve valley once more (Lliboutry, 1956). A second period of advance subsequently occurred between 1945 and 1962 leading to the reformation of Greve Lake and the splitting of frontal margins into the northern (calving into the freshwater Greve Lake) and southern termini (calving into the tidewater Eyre Fjord) (Rivera, 1992). For the northern terminus, this advance continued un-abated into the mid 1990s, increasing in magnitude from ∼1993. The southern terminus also continued to advance up until 1981, reaching what then represented a Neoglacial maximum (Warren and others, 1997). After reaching this maximum, the southern terminus went through a period of fluctuation, experiencing a large retreat up to 1989, before advancing in the early 1990s (reaching a new maximum in 1993) and then retreating once again in the mid- to late-1990s. Both the southern and northern termini began a general advancing phase once more between 2000 and 2006, respectively (Sakakibara and Sugiyama, 2014).
Rivera and others (1997) attribute this frontal behaviour to the following glacier surge triggers: (1) enhanced subglacial water pressure – modulated by internal ice mechanisms, fjord/proglacial lake depth, and meltwater input, among others (Sugiyama and others, 2011); (2) fluctuations in geothermal activity; (3) enhanced precipitation accumulation – Glacier Pio XI has an estimated accumulation area ratio of ∼0.8 (Rivera and Casassa, 1999; De Angelis, 2014); and (4) proglacial sedimentation. However, in the absence of further investigation, these factors, including others, are difficult to assess, hence why the importance of this study.
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