With Earth Day rapidly approaching, it seems like the perfect time to discuss recent climate science findings. Let's take a peek at the glaciers of the Patagonia region of Chile and Argentina. As the freshwater source for the region, the health of these glaciers is significant. Here is a look at the glaciers and major outflow lakes, courtesy of NASA.
Changes in Patagonian glaciers along the spine of the Andes have attracted the attention of scientists for decades. Satellite imagery studies of these glaciers have indicated rapid loss of ice volume during the last thee decades of the 20th century. These studies computed volume based on comparison of satellite images relative to cartographic measurements of the receding footprint of the 60 largest glaciers. This evidence, along with photographic evidence of changes in glacier profiles, have been used by environmental organizations to raise awareness of climate change.
A recent study by a team of British and Swedish scientists provides the most comprehensive look at the erosion of Patagonian glacial ice in the empirical record. The study is unique in scale and time frame. Researchers examined ice mass loss from 270 glaciers in the region from their Holocene epoch peaks during the "Little Ice Age" using geophysical and biological markers.
The study was designed to address the question of how much the rate of retreat of the glaciers has changed since their peak during the Little Ice Age. This peak occurred around 1870 for the northern glaciers of the region and 1650 for the southern glaciers. The research team combined the use of satellite imagery and field analysis of rock, soil, and plant morphology to reconstruct the footprint of the glaciers over time.
This photograph of the Franz Joseph glacier in New Zealand illustrates the basic idea. For this glacier, the maximum was reached in 1750. You can see how vegetation and ground contours mark the retreat of the glacier through 1989.
The satellite image below is one of the Patagonian glaciers evaluated in the study. The researchers used composite imagery to estimate current ice volume of the glacier. Ground measurements and sampling were then used to reconstruct the retreat of this glacier at various points in time from its 1650 maximum (shown as a orange line).
This is a painstaking process for one glacier to reconstruct ice volume over time. Now multiply that process by 270 glaciers. By combining all the ice volume data, the researchers were then able to estimate the contribution of glacial melt to sea level rise using a two-step computation.
Ice-volume changes were converted into sea level contribution in two steps, assuming glacier ice has a density of 0.911 and an area of ocean of 362 million km2 (www.worldatlas.com).
The two steps are as follows:
1. Convert ice volume into water equivalent volume (weqv):
weqv (km3) = ice volume (km3) x ice density
2. Convert weqv into sea level equivalent (sle):
sle = weqv (km3) / total area of ocean (km2)
The total ice lost and corresponding freshwater runoff contribution since the Little Ice Age maximum is impressive.
We estimate that the North Patagonian Icefield has lost 103±20.7 km3 of ice since its late Holocene peak extent in AD 1870 and that the South Patagonian Icefield has lost 503±101.1 km3 since its peak in AD 1650. This equates to a sea-level contribution of 0.0018±0.0004 mm yr−1 since 1870 from the north and 0.0034±0.0007 mm yr−1 since 1650 from the south
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More impressive is that the rate of change has been accelerating during the past 50 years. In fact, the researchers estimate that the loss of ice volume has been "between 10 to 100 times faster" during recent decades than throughout previous centuries from the maximum.
These changes parallel rising temperatures in the southern hemisphere, although temperature may not be the only factor driving glacial ice loss. It does make you wonder what the future holds for the region as global temperatures continue to increase.
Glacial melt is an important but relatively small component of sea level rise. About 10% of sea level rise is attributable to glacial melt. For the people of the Patagonian region, sea level rise is likely to be the least of their worries when it comes to the loss of glacial ice.
First and foremost, glaciers are primary source of freshwater for the region. Retreating glaciers will mean less and less freshwater availability, particularly during the warmer growing season. The region is largely arid, essentially a high desert, and water rights and availability have increasingly become flashpoints for conflict.
Thanks in no small part to the village idiots at the World Bank, Chile adopted privatization as the key principle governing water access and availability. Like every instance of regulating scarce natural resources via the "free market," this experiment has been a failure for the society while benefiting agribusiness and mining industries. The businesses that control much of the areas water resources are further degrading those resources by poor land management, excess consumption, and pollution. Add climate change to the mix, rapidly shrinking the freshwater storage in glaciers, treating water as a commodity will mean increasing cost and decreasing availability for many in the population. It remains to be seen whether the new fetish of dams will improve or exacerbate water problems.
While privatization fever has been less systematically practiced in Argentina, the issues of access compounded by industry practices and control are also in evidence. Deforestation to promote agriculture in arid and semi-arid regions has produced widespread land degradation, which accelerates evaporation and runoff of precipitation. There is an effort to reforest some of the areas, but trees grow slowly in this area and the impact of climate change on glacial water storage appears to be outpacing mitigation and adaptation.
Canadian mining company Barrick, poster child for eco-injustice in the Patagonian region
March 4, 2010 – Tudcum, San Juan – Argentina. Rising cases of diarrhea, leukemia, recurring and persistent drought, the appearance of putrid mud on river banks, the disappearance of local fauna and flora, consistently falling crop yields, and a general reduction in water supply, have culminated(exhausted) the patience of local communities in mining enclaves of the Andes who have been promised prosperity and development from gold mining investments but have only seen a deteriorating environment, falling crop revenues, increased health illnesses and rising social strife due to violence, prostitution and drug use as workers from outside localities flock to work in Barrick Gold’s mining projects. Tudcum, the closest Argentine town to Barrick Gold’s Veladero and soon to arrive Pascua Lama gold mines has taken to the streets to declare their opposition to Barrick.
Gold mining uses extravagant amounts of water and cyanide to process the ore. The discharge described by locals is much more toxic than your garden variety acid mine drainage.
The impact of climate change on glacial ice will also increase glacial lake outburst floods, affectionately known as GLOFs or jökulhlaups. There has been an increase in catastrophic floods from GLOFs in recent years, corresponding to rapid loss of glacial ice and rapid melt runoff into lakes. The mechanism thought to be responsible for flooding is the formation of subglacial tunnels or channels that concentrate erosive forces. Erosion and sediment deposition from GLOFs pose severe risks and engineering challenges to dams being planned in the Patagonian region.
Last but not least, sediment deposition from glacial melt impacts freshwater ecosystems. This comes from selection pressures on plankton species from sediment clouding.
The input of glacial flour creates a subhabitat that can function as a refuge for species that are sensitive to high PAR and UVR exposure. When the glacier has vanished, this habitat may disappear. During the melting period, with heavy sediment input, we predict that competitive species in transparent waters, like Chrysocromulina, picocyanobacteria and copepods, will become less common. The deep Chl a maxima is also likely to become less developed. Hence, glacier melting will probably have profound effects on both species composition and behavior of several planktonic taxa with potential effects on the food web.
Welcome to the brave new world.