Posts Tagged global warming glacier

Paradise Glacier Ice Caves Lost

From the 1930′s through the early 1980′s Paradise Glacier’s ice caves were world famous. Today they are gone. In 1906 Paradise Glacier was a single glacier that extended down to an elevation of 6000-6200 feet. The image below is from the book The Mountain that was God. In the 1930′s the glacier separated into an upper and a lower part. The caves were in the lower part, that filled a relatively flat valley at an elevation of 6500 feet. Ice caves cannot form beneath a glacier that is moving substantially, as the movement would close up the cavities. Ice caves form under stagnant, melting sections of the glacier. The 1971 USGS map, see below, indicated the lower Paradise Glacier was 1.1 km long and had an area of .14 square kilometers. By 1981 the glacier had retreated to the upper half of the valley that had been filled with ice caves, second image below. In the 1981 image, from Jim Kuresman, note the mountain peak in the center that is in the 1906 image as well. There is no remaining snowcover either on the lower glacier, a glacier cannot survive without an accumulation zone that has significant persistent snowcover even at summers end. In 1985 I visited the ice caves, and they were still impressive, although much reduced in size, number and length. i returned to the ice caves in 1993 and found no ice caves remaining and no glacier either. The Paradise Ice Caves valley in 2005 (Greg Louie) and 2007 (David Head image) is beginning to sprout some vegetation where hikers tread through ice caves a generation before. The glacier fits the regional pattern of glacier retreat and loss. You can observe in the upper left of the 2005 and 2007 images that the upper Paradise Glacier still exists, though it is retreating, the last picture is the terminus of the upper Paradise Glacier. In 2009 the upper Paradise Glacier lost all of its snowcover, not a good sign for its long term survival. Below is the Google Earth view of the area from 2009 imagery. A comparison with the map indicates that not only has the lower Paradise Glacier been lost, but so has the Williwakas Glacier.

Comments (2)

Fleming Glacier Acceleration and Retreat, Antarctica

Recent observations indicate that the Fleming Glacier on the Antarctic Peninsula which used to feed the Wordie Ice Shelf is accelerating and thinning even faster(Wendt et al, 2010) This is leading to the production of numerous tabular icebergs from the glacier front as seen below from a 2009 Google Earth image. . A is a rift that is also the ice front toward the upper right. B and C are rifts that will produce future tabular ice bergs. D is an iceberg with an area of just under 1 square kilometer. Wordie Ice Shelf was the northernmost large Ice shelf on the western AP. The ice shelf disintegrated between 1970 and 2000. From an area of 1900 km2 in 1970 to 100 km2 in 2009 as mapped by the British Antarctic Survey. The first image is from the BAS in 1989. Followed by a series of maps illustrating its demise put together by the BAS and USGS The breakup was suggested to have occurred due to a warming trend in the region that began in the 1970’s generating meltwater . There is also thinning and weakening around some of the pinning points where the ice shelf was grounded. This is similar to observations from Wilkins Ice Shelf.
The Wordie Ice Shelf was fed by several major tributary glaciers including the Fleming Glacier.
(Rignot and others (2005) used satellite radar interferometry to observe changes in behavior of Fleming Glacier from 1995 to 2004 identifying a 40-50% increase in glacier velocity from the terminus to 50 km above the terminus and a two meter per year thinning. More recent Airborne thickness data indicate thinning has increased to 3 or 4 m per year in the lower reach of the glacier during the 2004-2008 period (Wendt et al, 2010). Rignot and other (2005) further observed that 6.8 ± 0.3 km3/yr of ice, which is much larger than snow accumulation of 3.7 ± 0.8 km3/yr. This imbalance has certainly increased with acceleration.
Without the presence of a thick, slow moving ice shelf buttressing the Fleming Glacier it has accelerated. Below is a map from Wendt et al (2010) showing the Fleming Glacier former margins. Below that is Google Earth Image showing the nature of the calving front. Notice the tabular ice bergs that have and are about to break off. Below that is an image further up glacier, a nunatak has appeared in mid glacier that is not evident in the 1989 image. As observed for the Jakobshavn and Pine Island Glacier thinning leads to reduced buttressing and increased glacier flow.

Comments (2)

North Cascade Glacier 2010 Mass Balance Forecast

Beginning in 2006 the North Cascade Glacier Climate Project began to forecast glacier mass balance from atmospheric circulation index data. To be useful for water resource managers such a forecast must be made early in the spring. This is when snowpack begins melting at elevations below the glaciers and reservoirs can begin to be recharged. A first generation forecasting model that relied on October-March Pacific Decadal Oscillation and El Nino Southern Oscillation Index values was developed. The mass balance forecast method reliably determined if the mass balance of North Cascade glaciers would be negative, equilibrium or positive in 22 of the last 26 years. Most people may be under the impression that the snowmelt season is well underway, in fact 2010 has seen a record loss of snowpack extent through March this year in North America. A look at the snow cover depletion using data from the Rutgers Global Snow Lab beginning in either the 7th, 8th or 9th week and ending with the 14th week indicates this record melt. In the second image the rapid snow cover loss is further apparent. In the Northern Hemisphere for example February 2010 was the third most extensive snow cover extent of the last 44 years, March the 18th of the last 44 years, and April the 41st most of the last 44 years (Rutgers University Global Snow Lab). This change indicates a record snow cover melt off in 2010 for the last 44 years. This can happen on a glacier as well.However, for glaciers the snowmelt season usually ends close to May 1. The melt season in the North Cascades is still not upon us. Typical maximum accumulation occurs around May 10. The best long term snowpack data is for April 1, hence that date is often used to evaluate the end of winter snowpack for snow measurement stations most of which are well below glacier elevations. This year snowpack on April 1 averaged 0.82 meters. There has been no year with positive mass balance and snowpack on April 1 below 1.0 meters. If we look solely at the indices both PDO and ENSO had positive values this winter. This is similar to the case in 1987, 1993, 1994, 1995, 1998, 2003, 2004,and 2005 all negative balance years. The rule for the model is that if PDO and ENSO are positive glacier mass balance will be negative. Both of the indices reflect sea surface temperature in the Pacific, and positive values favor warmer SST’s near the west coast. Lastly we have the temperature forecast from NOAA for spring which for the area shows a high degree of confidence for above normal temperatures from April-June. All of the above indicate glacier mass balance will be negative in the North Cascades this year even though the galciers are deeply buried in snow right now.

Comments off

Anderson Glacier Retreat, Middle section exposed

Anderson Glacier is the headwaters of the Quinault River in the Olympic Mountains of Washington. A century ago the glacier was 2 km long, and a half kilometer wide. Retreat of this glacier in the first half of the 20th century exposed a new alpine lake, as the glacier retreated 1 kilometer. From 1950-1980 the glacier diminished slowly. From 1959 to 1990 the glacier thinned and retreated from the lake trapped behind the Little Ice Age moraine. The picture below was given to me by Austin Post. Since 1990 the glacier has begun to shrink rapidly. The USGS aerial photograph of the glacier is from 1990, Anderson Glacier is on the right, West Glacier is to the left. Investigating this glacier in 1992 we measured its area at 0.38 square kilometers, down from 1.15 square kilometers a century before. Ten years later the glacier had diminished to 0.30 square kilometers, but had thinned even more, leaving it poised for a spectacular change, over the next five years. Large outcrops of rock have appeared beginning in 2003 and further exposed in 2005 and 2009 in the middle of the glacier. Note the outcrops in this 2007 image from Kathy Chrestensen The end of the glacier is an avalanche runout area and is thinning slower than most of the lower reach of the glacier. This glacier has become a series of small disconnected relict glacier ice patches. There are some large ice caves that have developed under the glacier. This is an indication of limited flow, and stagnant melting ice. Anderson Glacier is not the only glacier feeding the Quinault River, all the others are retreating as well. The result of glacier retreat is reduced late summer and early fall streamflow, impacting salmon runs at that time of the year. This is primarily the fall Coho, Chum and Chinook salmon and Steelhead summer run. During the spring and early summer runoff increases as snowmelt still occurs, but is not retained in the glacier system.

Comments off

Zemestan Glacier, Afghanistan Retreats

The Wakhan Corridor in Afghanistan is not easy to get to, as a result field study of its glaciers are quite limited. This is where the Global land ice Monitoring System (GLIMS) comes in. GLIMS acquires satellite imagery of glaciated areas, making these images available to researchers and processing them to an extent for inventory purposes. GLIMS is led by Jeff Kargel at the University of Arizona. In the Wakhan Corridor a group of glaciers was examined by Umesh Haritashya and others (2009). This recent GLIMS project examined ASTER and Landsat MSS data 1976–2003, in the Wakhan Corridor of Afghanistan. Of the 30 alpine glaciers of varying type, size and orientation examined 28 glacier-terminus positions have retreated, two have been stationary. The largest average retreat rate was 36 m per year, and the average retreat was 11 m per year. The retreat is evident in a comparison of 1998 Landsat and 2010 Landsat images, note the orange arrow in both. The width and length of the terminus tongue has changed. One of the glacier examined was the Zemestan Glacier. This glacier is 5.3 kilometers long, has an area of 5.2 square kilometers, begins at 5640 meters and terminates at 4800 meters. It is one of many glacier in the Central area of the Wakhan Corridor. Zemestan Glacier has retreated at a rate of 17 meters per year over the study period, a total retreat of 460 meters, 9% of its total length. A comparison of 1998 and 2010 Landsat imagery indicates the retreat of the terminus tongue in width and length at the orange arrows. The glacier has remained snowcovered at its higher elevations at the end of the summer in recent satellite images. This indicates that with current climate the glacier does have a significant accumulation zone and can survive current climate. Continued warming will increase the retreat rate and could threaten its survival. The glacier feeds the Pamir River which in turn drains into the Panj River, to the Amu Darya River and then the Aral Sea. The terminus is on a shallow slope lacks a steep slope and is not extensively crevassed. All of these factors indicate retreat will continue. The glacier has little debris cover unlike many glaciers in the Karakoram-Himalaya-Pamir Ranges such as the Khumbu Glacier or the Zemu Glacier

Comments off

Tasman Glacier Retreat

Update for 2/22/2011-the Tasman Glacier’s thin and weak terminus area, see in the GE image below, in Tasman Lake shed some large icebergs due to the earthquake generating some substantial waves in the lake. The post earthquake image with numerous fresh icebergs is the second below and is from the EPA. No word on the Hooker Glacier in the next valley west, which also calves into an expanding lake or Murchison Glacier in the next valley east. There is a Tasman Glacier update in 2013.. The New Zealand National Institute of Water and Atmospheric Research has been examining the changes in volume and snowline on New Zealand Glaciers since 1977. This survey has concluded for 2009 they same observation as for 2007 and 2008, the glaciers are shrinking. An examination of the recent volume changes on the glacier indicate that the volume has been particularly negative since 1998.. This followed a period of relatively positive mass balance from 1990-1997, which made the New Zealand glaciers the least rapidly retreating glaciers in the world. For Tasman Glacier the retreat has been ongoing, the NWIA has noted a retreat of 180 m per year on average since the 1990′s. The proglacial lake at the terminus continues to expand as the glacier retreats upvalley. The lake is deep with most of the lake exceeding 100 metes in depth, and the valley has little gradient, thus the retreat will continue. It has been noted by researchers at Massey University that it is just to warm for the terminus area at 730 m to endure. Imagery of Tasman Glacier indicates the future it faces. There was no lake in 1973 and now it is more than 7 km long. The glacier appears quite rotten along the ice margin and poised for further retreat. The glacier drains a valley just east of the highest mountains in the range Mount Cook and Mount Tasman. . The image above has a blue line up the center of the glacier from the former terminus at the end of the lake too the head of the glacier. The upper image is from 2007 and the lower image from 2009. In the latter image the lake has expanded considerably. The disconnected lakes and debris covered ice on the left side-west side of the glacier has been replaced by all lake. Icebergs are afloat in this lake, they do not survive very long. The debris cover itself insulates the glacier ice from melting, slowing the process. However, the process due to the warmth and increased melting of the last decade has been increasing.

In the image below is a closeup of the section of ice that has now disintegrated, before it did. You can see the crevasses in some of the icebergs too. This is a rapidly changing environment due to the ongoing climate warming.

Comments (1)

Follow

Get every new post delivered to your Inbox.

Join 102 other followers

%d bloggers like this: