The Need for a Global Paleoclimate Observing System (original) (raw)
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Modern glacier retreat on Kilimanjaro as evidence of climate change: observations and facts
International Journal of Climatology, 2004
In recent years, Kilimanjaro and its vanishing glaciers have become an 'icon' of global warming, attracting broad interest. In this paper, a synopsis of (a) field observations made by the authors and (b) climatic data as reported in the literature (proxy and long-term instrumental data) is presented to develop a new concept for investigating the retreat of Kilimanjaro's glaciers, based on the physical understanding of glacier-climate interactions. The concept considers the peculiarities of the mountain and implies that climatological processes other than air temperature control the ice recession in a direct manner. A drastic drop in atmospheric moisture at the end of the 19th century and the ensuing drier climatic conditions are likely forcing glacier retreat on Kilimanjaro. Future investigations using the concept as a governing hypothesis will require research at different climatological scales.
A century of ice retreat on Kilimanjaro: the mapping reloaded
The Cryosphere, 2013
A new and consistent time series of glacier retreat on Kilimanjaro over the last century has been established by re-interpreting two historical maps and processing nine satellite images, which removes uncertainty about the location and extent of past and present ice bodies. Three-dimensional visualization techniques were used in conjunction with aerial and ground-based photography to facilitate the interpretation of ice boundaries over eight epochs between 1912 and 2011. The glaciers have retreated from their former extent of 11.40 km 2 in 1912 to 1.76 km 2 in 2011, which represents a total loss of about 85 % of the ice cover over the last 100 yr. The total loss of ice cover is in broad agreement with previous estimates, but to further characterize the spatial and temporal variability of glacier retreat a cluster analysis using topographical information (elevation, slope and aspect) was performed to segment the ice cover as observed in 1912, which resulted in three glacier zones being identified. Linear extrapolation of the retreat in each of the three identified glacier assemblages implies the ice cover on the western slopes of Kilimanjaro will be gone before 2020, while the remaining ice bodies on the plateau and southern slopes will most likely disappear by 2040. It is highly unlikely that any body of ice will be present on Kilimanjaro after 2060 if present-day climatological conditions are maintained. Importantly, the geo-statistical approach developed in this study provides us with an additional tool to characterize the physical processes governing glacier retreat on Kilimanjaro. It remains clear that, to use glacier response to unravel past climatic conditions on Kilimanjaro, the transition from growth to decay of the plateau glaciers must be further resolved, in particular the mechanisms responsible for vertical cliff development. Kibo, because of their location and exceptional elevation, offer a unique location to sample atmospheric conditions in the tropical mid-troposphere, which is extremely valuable given the influence of low latitude weather and climate processes on global circulation (e.g. Chiang, 2009). Recent field experiments, complemented with atmospheric and glaciological modelling, have shed new light on the linkages between atmospheric processes across multiple space and time scales and changes to glacier mass on Kilimanjaro (e.g.
Climate Change: The Evidence and Our Options
Glaciers serve as early indicators of climate change. Over the last 35 years, our research team has recovered ice-core records of climatic and environmental variations from the polar regions and from low-latitude high-elevation ice fields from 16 countries. The ongoing widespread melting of high-elevation glaciers and ice caps, particularly in low to middle latitudes, provides some of the strongest evidence to date that a large-scale, pervasive, and, in some cases, rapid change in Earth's climate system is underway. This paper highlights observations of 20th and 21st century glacier shrinkage in the Andes, the Himalayas, and on Mount Kilimanjaro. Ice cores retrieved from shrinking glaciers around the world confirm their continuous existence for periods ranging from hundreds of years to multiple millennia, suggesting that climatological conditions that dominate those regions today are different from those under which these ice fields originally accumulated and have been sustained. The current warming is therefore unusual when viewed from the millennial perspective provided by multiple lines of proxy evidence and the 160-year record of direct temperature measurements. Despite all this evidence, plus the well-documented continual increase in atmospheric greenhouse gas concentrations, societies have taken little action to address this global-scale problem. Hence, the rate of global carbon dioxide emissions continues to accelerate. As a result of our inaction, we have three options: mitigation, adaptation, and suffering.
Global Disappearance of Tropical Mountain Glaciers: Observations, Causes, and Challenges
Geosciences, 2019
This article reviews the current status of tropical glaciers in the South American Andes, East Africa, and Australasia by shedding light on past, present, and future glacier coverage in the tropics, the influence of global and regional climates on the tropical glaciers, the regional importance of these glaciers, and challenges of ongoing glacier recessions. While tropical glaciers have predominantly receded since the Little Ice Age, the rate of shrinkage has accelerated since the late 1970s as a result of climate changes. As a result, socio-ecological implications occur around ecosystem health, natural hazards, freshwater resources, agriculture, hydropower, mining, human and animal health, traditions and spirituality, and peace.
Irregular tropical glacier retreat over the Holocene epoch driven by progressive warming
The causes and timing of tropical glacier fluctuations during the Holocene epoch (10,000 years ago to present) are poorly understood. Yet constraining their sensitivity to changesin climate 1 is important, as these glaciers are both sensitive indicators of climate change and serve as water reservoirs for highland regions 2 . Studies have so far documented extra-tropical glacier fluctuations 3,4 , but in the tropics, glacier–climate relationships are insufficiently understood. Here we present a 10 Be chronology for the past 11,000 years (11 kyr), using 57 moraines from the Bolivian Telata glacier (in the Cordillera Real mountain range). This chronology indicates that Telata glacier retreatedirregularly.A rapidandstrongmeltingfromthe maximum extent occurred from 10.86 0.9 to 8.5 6 0.4 kyr ago, followed by a slower retreat until the Little Ice Age, about 200 years ago. A dra- matic increase in the rate of retreat occurred over the twentieth century. A glacier–climate model indicates that, relative to modern climate, annual mean temperature for the Telata glacier region was 23.3 6 0.8 6C cooler at 11 kyr ago and remained 22.1 6 0.8 6C cooler until the end of the Little Ice Age. We suggest that long- term warming of the eastern tropical Pacific and increased atmo- spheric temperature in response to enhanced austral summer insola- tion were the main drivers for the long-term Holocene retreat of glaciers in the southern tropics.
Glaciers receive more attention in the climate change debate given their high susceptibility to warming. Long records of direct measurements of glacial processes, however, are limited; as a result, reliable annual mass balance records usually cover less than a century. Tropical examples that are believed to be more sensitive to climate change are among the least studied glaciers worldwide. We present the longest known annual glacial retreat record extending to the present, based on annual moraines formed at the retreating terminus of the Tarija Glacier, in the Bolivian Andes. The availability of high-resolution satellite imagery confirms how these ridges form, substantiating a 258-year glacial retreat history. The annual retreat record is validated by correlation with Lake Titicaca surface level evolution: the highest ablation rate matches the highest lake level (1986-1987). Glacial retreat also matches well with a large Pampean foreland lake level evolution (Mar Chiquita), suggesti...