Verde Glacier is adjacent to Reichert Glacier and drains the north side of the Northern Patagonia Icefield. It is a small glacier compare to many outlet glaciers of the icefield that have been examined in previous posts, Reichert Glacier, Steffen Glacier, Nef Glacier, and Colonia Glacier. Here we examine Landsat imagery during the 1998-2014 period to identify the response of the glacier. The glacier flows from a pair of peaks at 1800 m to terminate at the edge of a proglacial lake. There is a significant icefall at 800-1250 m and a significant avalanche fan at the base of this icefall that is spills from a disconnected portion of the glacier west of the terminus and just northwest of the icefall. Davies and Glasser (2012) Figure 2d indicates the glacier nearly filling the entire lake in 1975. In Figure 8a they indicate the fastest retreat for the glacier being from 1998-2014. Rivera et al (2007) indicate the ELA for the glacier at the top of the icefall 1250 m.
The yellow arrow in each image is the 2014 terminus and the red arrow the 1998 terminus. In 1998 the glacier terminates at the red arrow just beyond the northeast bend in the lake. The lake is 1.6 km long. By 2001 the glacier has retreated 300 m and is at this bend. Notice that the lowest lone kilometer of the glacier is quite debris covered. By 2014 the glacier has retreated to the yellow arrow, this is a further 600 m retreat since 2011. The lake is 2.5 km long measured along its center line. The 900 meter retreat in 16 years is substantial for a glacier that is only 5 km long. A cloe up view of the terminus in a Goggle Earth image indicates that the lowest 300 m is debris coverered ice, notice the wetness of some of the debris, pink arrow. This looks more like ice cored moraine than active glacier ice covered by debris. If this is the case the active terminus is 300 m from the shore of the lake, at the yellow terminus where calving begins. It is certain the lake will expand further as the buried ice melts, but it is nearing its southwestern limit. The steep slope of the icefall and the rock slope to the right of the icefall is evident. This will lead to continued avalanching onto the terminus area, that will make that lowest region above the yellow arrow more difficult to melt out. One observation that is striking is the number of narrow alpine lakes that have formed and expanded as the Northern Patagonia Icefield outlet glaciers have receded.
1998 Landsat image
2001 Landsat image
2014 Landsat image
Google Earth image
Glaciar Chico drains the east side of the Southern Patagonia Icecap (SPI). Rivera et al (2005) noted that Glaciar Chico had retreated significantly from 1945 to 1976, calving into Brazo Chico, but then retreated slower than most SPI glacier from 1975 to 2001, second image from Rivera et al (2005).
Davies and Glasser (2012). noted that Glaciar Chico’s thinning rates are comparable to other glaciers of the SPI, and the rate of area SPI now shrinking at 20.5 km2 per year. Here we examine Landsat imagery of the glacier from 1986, 1999, 2011 and 2013. In 1986 the glacier terminates near the northern end of a small island in Brazos(Lago) Chico, yellow arrow. A portion of the terminus extends due north to Glacier O’Higgins forming two proglacial lakes, red arrow. The red dot and pink dot indicate the 2013 terminus positions. By 1999 the island is half exposed, a retreat of 600 m. By 2011 the glacier has exposed nearly the full island a retreat of 900 m. The northern margin at the red arrow has also retreated 300 m and the proglacial lakes have now drained. By 2013 at the beginning of the melt season, Glaciar Chico has retreated from the island, and is ending in the lake, though the lake is not likely very deep. The glacier has retreated 1100-1200 meters from its 1986 position. The northern margin has retreated 400-500 meters from its 1986 position. This indicates widespread thinning has continued as Rivera et al (2005) and Davies and Glasser (2012) have indicated would be the case. At the orange arrow 5 km above the terminus the glacier width has decreased by 15-20% from 1986-2013, indicating a continued reduction of flow of ice into the terminus region. The closeup of the terminus from Google Earth indicates a glacier with active crevassing and flow into the terminus region, suggesting that rapid retreat will not ensue. The retreat of this glacier is typical of the other Patagonian glaciers as Davies and Glasser (2012) have so well documented. Examples of the retreat include Onelli Glacier, Jorge Montt Glacier, and Glaciar Steffen
1986 Landsat image
1999 Landsat image
2011 Landsat image
2013 Landsat image
Google Earth terminus closeup
The Gran Campo Nevado (GCN) is the smallest of the four primary Patagonian Icefields. It is on the Península Muñoz Gamero 200 km to the south of the Southern Patagonia Icefield. The major outlet of this icefield is the Noroeste Glacier. In a recent paper examining the changes in Patagonia glacier from 1870-2010 (Davies and Glasser, 2012), observed that the Gran Campo Nevado icefield lost of its area from 1870-2010, and 14% of its area from 1986-2011. Davies and Glasser (2012), Aberystwyth University, also documented that 21 of the 31 glaciers of the icefield experienced their most rapid retreat of the last 140 years during the 1986-2010 period. Nororeste Glacier has been a focus in two papers Scheider et al,(2007) and Moller and Schenider (2010). These papers document a retreat of 1100 m from 1986-2002 first image below, they further identify that the glacier area has declined by 4 square kilometer from 1986-2007, and in 2007 was just under 50 square kilometers. Moller and Schenider (2010) develop an areal extent model for the glacier that indicates the glacier will lose a further 15 square kilometers by 2100. The second image is showing the areal extent change from Davies and Glasser (2012), with the red arrow indicating Nororeste Glacier and the yellow the deglaciated area since 1870. Here we examine Landsat imagery from 1999, 2007 and 2012. The 1986 terminus is noted by the orange line, the 2002 margin is a yellow line, the 2007 terminus a purple line and the the 2012 terminus indicated by pink arrows. The retreat from 1986-1999 was 600 meters, from 1999-2007 1050 meters and 2007-2012 250 meters. The overall retreat of 1900 meters from 1986-2012, is 73 meters/year and from 1999-2012 the 1300 meter retreat is 100 meters/year. One other noteworthy change is the thinning and retreat at the northern margin that has led to the drainage of an. ice dammed lake that is present in 1999, red arrow and gone in 2012. The lake had drained by 2007 but that is not evident in the deep shadows of the Landsat image. This glaciers retreat fits the regional patter of glaciers to the north, Joerg Montt Glacier, Colonia Glacier, Glacier Gualas and Alemania Glacier to the south. This also fits the overall pattern of area loss that increased after 1986 and has remained high (Davies and Glasser, 2012) and the ongoing detailed studies of the Chilean Laboratorio de Glaciologia
The retreat is partly due to calving of icebergs into the lake the glacier terminates in, as evident by the icebergs visible in each satellite image above and in the Google Earth image below of icebergs in the lake in 2004.
The Jorge Montt Glacier is one of the main tidewater glaciers of the Southern Patagonia Icefield. The glacier has been the focus of ongoing annual observations by the Laboratorio de Glaciologia at the Center for Scientific Studies, University of Chile. Two recent papers highlight the dramatic changes this glacier is undergoing. The glacier has retreated 19.5 km from 1898-2011 (Rivera et al, 2012a). A recent photograph of the terminus from Andrés Rivera indicates the extensive crevassing and calving of icebergs indicating the high very high velocities.. The velocities were determined from tracking of salient features for an 11 month period using time lapse photography and indicated a mean velocity of 13 meters/day, with maximum velocities of up to 33 meters/day, in the center of the glacier (Rivera et al, 2012b). These velocities rival the high velocities on the faster Greenland outlet glaciers and San Rafael Glacier, Chile. They did not observed seasonal velocity changes. This paper provides a nice visual of the velocity, top image. The velocity and retreat tend to increase when water depth increases. The mean water depth at the calving front has declined from over 260 m 1997-2003 to closer to 220 m 2003-2011, bottom image indicates the water depths from Rivera et al (2012a). . . A map of the long term retreat of the glacier is provided in both papers, here we examine a closeup view of the lower glacier from Landsat imagery in 1997, 2003 and 2011. The glacier retreat peaked during the 1990-2000 period with 8.5 km of retreat. The lake widened and deepened at the calving front for that period. The yellow arrow indicates the 1997 terminus, burgundy arrow 2003 and orange arrow 2011. The green arrows point the expansion of exposed bedrock areas on the east margin of the glacier from 1997-2011. Retreat from 1997-2003 was 2250 m, 375 m/year. Retreat from 2003-2011 was 2000 meters, 250 m/year. In 2011 an additional nunatak has emerged as the glacier has thinned. The 2011 terminus is near a point where the lake appears it will widen again, the potential depth is hard to assess. The map from Rivera et al (2012a) indicates at least a short term deepening at the ice front, this is at the same point as a modest lake width reduction. . Below is a closeup of the changes 12-14 km upglacier of the terminus indicating the rapid thinning from 2003 to 2011 expanding the bedrock exposed at point B and exposing the new nunatak at Point C. The retreat of this glacier follows the regional pattern observed by the Laboratorio de Glaciologia on other glaciers such as Gualas Glacier, Nef Glacier, Alemania Glacier, Tyndall Glacier and Colonia Glacier.
Tyndall Glacier is a large outlet glacier of the Southern Patagonia Icefield (SPI). This glacier has an area of over 300 square kilometers. The main glacier terminus ends in Lago Geikie, which began to form around 1940, and the east terminus previously terminated in Lago Tyndall. Raymond et al (2005) report that the glacier had receded 5 km from 1945 to 2001. The retreat is illustrated in a figure from Rivera & Casassa (2004). This web page on the Tyndall Glacier is one of many provided by Andrés Rivera at the Laboratorio de Glaciología at Universidad de Chile. Assessing the ice surface elevation changes on three profiles 8-15 km above the terminus, the amount of thinning was determined by Raymond et al (2005). From 1945-2002 the average thinning rate of the glacier at meters was 2.3 meters per year. The rate has accelerated averaging over 3.3 meters per year since 1985. This has driven the retreat. Lago Geikie is a deep lake with maximum depths reaching 400 meters and was 300 meters at the calving front in 2001 Raymond et al (2005) . This allows for considerable calving of the thick Tyndall Glacier, which is grounded on the bottom of the lake at its terminus. The glacier velocity near the calving front is 700 meters per year. A comparison of the terminus position from the aforementioned papers, Google Earth from 2003 (top Image) and a Geoeye image from 2010 (bottom image) indicates the changes of Tyndall Glacier are ongoing. Lago Tyndall (LT) for example is continuing to contract as the terminus (TE) that feeds it has thinned and pulled back from the valley that feeds it. Increasingly this is becoming a watershed that will not be fed by Tyndall Glacier. Lago Geikie (LG) continues to expand now 7 km long. The retreat in the last 7 seven years has been 600-900 m on the main calving front. This has exposed a new peninsula (P). The glacier terminus is much narrower than in 1975 in an aerial image from Raymond et al (2005). The snowline on the glacier is at 900 meters and there is considerable glacier area above 1200 meters, indicating this glacier can survive additional warming, note the above image. As Raymond et al (2005) emphasized the glacier bottom remains below the Lago Geikie lake level for 14 km. Over much of this distance calving would play a role, helping continue the recent retreat. This retreat due to calving into a glacier lake resulting from ongoing glacier thinning resulting from increased surface ablation is widespread from Bear Glacier, Gilkey Glacier and Yakutat Glacier in Alaska, to Tasman Glacier in NZ to Nef Glacier and Colonia Glacier in
Colonia Glacier drains east from the Northern Patagonia Icefield feeding the Baker River, Chile. The recent substantial retreat of Colonia Glacier like Glacier Nef just to its north is posing new hazards. The glacier is unusual in the number of lakes that are adjacent to or feed into the adjacent glacier damed or proglacial lakes. In the image below Lake A=Arco Lake, Lake B=East Terminal Lake, Lake C=Cachet 1 , Lake D= West terminal Lake, Lake E=Colonia Lake and Lake F=Cachet 2. The glaciers recent retreat and glacier lake outburst floods have been closely monitored by the Laboratorio de Glaciología in Valdivia, Chile.Aniya and others (1999)observed that Colonia Glacier began a rapid retreat after 1985
Superimposition of a RADARSAT image from 1997 and a Landsat 1987 image indicated a retreat of
400 m, from 1997-2005 the retreat has further accelerated, with a general frontal retreat of 2.5 km. Rivera and others (2007) observed that the Colonia Glacier had lost 9.1 square kilometers of area from 1979-2001, which is 3% of the total glacier area. The Laboratorio de Glaciologia’s
In the spring of 2008 Baker River suddenly tripled in size, in less than 48 hours, roads, bridges, and farms were severely damaged. Lake Cachet 2 had vanished the 5 square kilometer glacial lake had emptied 200 million cubic meters of water in just a matter of hours. This lake drained beneath the glacier after sufficient water had filled the lake to buoy part of the glacier and subglacial conduits had begun to develop. Since Cachet 2 emptied in April 2008, the lake has emptied five more times October,
December 2008, March and September 2009 and March 2010, with peak flows released of 3000 cubic meters per second. Below are images of Cachet 2 half- full in Google Earth Imagery from Sept 2008 (note trimline above lake), and full after the flood on 5/28/2008 and empty on 4/8/2008, and lastly the image of the Colonia River’s wide fresh braided stream channel flowing into the Baker River. The newly deposited material from the flood is what makes the wide braided valley such a fresh sediment brown color. The two lakes at the terminus of the glacier did not exist in 1979, the western most terminus lake (B) drained into the easternmost terminus lake (D) via a sub-glacial tunnel after formation in the late 1980’s until 2005 when a channel was cut right through the glacier terminus. This is evident in the image below, there is still glacier ice on both sides of this drainage channel. The development and demise of glacier dammed lakes and the resultant problem of glacier lake outburst floods is not rare today, Imja Glacier, and Tulsequah Glacier are other examples. In the case of Baker River the outburst floods are a threat to the planned hydropower developments as documented by Dusaillant and others (2009). The Colonia Glacier retreat mirrors that of Glacier Nef the next major glacier to the north. Hidroaysen Project is proposing 5 dams on the Baker and Pascua River generating 2750 MW of power. Glacier Nef retreated 3400 m from 1945-2000, 2400 m retreat of the retreat occurred in the 1994 collapse of the terminus tongue into the proglacial lake, which is now 3.5 km long. This retreat includes that of , Gualas GlacierReichert Glacier, Steffen Glacier, and Nef Glacier.