Glacier Climate Interactions Research Articles

A revised chronology of key Vatnajökull (Iceland) outlet glaciers during the Little Ice Age

AbstractGlacier fluctuations from key Vatnajökull outlets have been redated using tephrochronology coupled with two lichenometric techniques to ascertain the timing of the Little Ice Age (LIA) maximum in southeast Iceland. An updated tephrochronology for southeast Iceland (both the number of tephra layers present and their geochemical signatures) indicates a LIA maximum for both glaciers between AD 1755 and 1873. Based on a population gradient approach, lichenometrically dated moraines along the margins of Skálafellsjökull and Heinabergsjökull narrow this window to the early to mid-19th century respectively. These revised chronologies, in addition to emerging evidence from elsewhere in Iceland, support a late 18th- to early 19th-century LIA glacier maximum. In contrast, the Norwegian LIA glacial maximum is strongly centred around AD1750. This implies differing glaciological responses to secular shifts in the North Atlantic Oscillation. Such revisions to the Vatnajökull record are crucial, as accurately identifying the timing and delimiting the spatial extent of the Icelandic LIA glacier maximum will allow further light to be shed on glacier–climate interactions in the North Atlantic.

Modern glacier retreat on Kilimanjaro as evidence of climate change: observations and facts

AbstractIn 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. Copyright © 2004 Royal Meteorological Society

Glacier-climate interaction at low latitudes

AbstractIn the low latitudes there is an absence of major thermal seasonality, yet there are three different climate regimes related to global circulation patterns and their seasonal oscillation: the humid inner tropics, the dry subtropics and, intermediate between these two, the outer tropics. For the respective glacier regimes the vertical profiles of specific mass balance (VBPs) are modeled considering vertical gradients of accumulation, air temperature and albedo, the duration of the ablation period and a factor for the ratio between melting and sublimation. The model is first calibrated with data from Hintereisferner, Austrian Alps, and is then applied to tropical conditions. The simulated VBP matches well the measured profiles from Irian jaya and Mount Kenya. Due to lack of field evidence, the subtropical VBP cannot be verified directly. However, application of the respective model versions separately to the humid and dry seasons of the outer-tropical Glaciar Uruashraju, Cordillera Blanca, Peru, provides reasonable results. Glaciers in the humid inner tropics are considered to be most sensitive to variations in air temperature, while dry subtropical glaciers are most sensitive to changes in air humidity. The two seasons of the outer tropics have to be viewed from these different perspectives.

A review of the modern fluctuations of tropical glaciers

The tropical climate is characterized by a homogeneous atmosphere without frontal activity, a lack of thermal seasonality, and by one to two differently pronounced precipitation seasons. Consequently, tropical climate has a characteristic impact on tropical glaciers, with glacier–climate interactions different from those of the mid- and high-latitudes. The glaciers of tropical South America, Africa and New Guinea had a general maximum extent during the Little Ice Age (LIA) and have receded since the second half of the 19th century. Since then the fluctuations have been differently pronounced in different regions, but their general behaviour has been largely synchronous. The retreat from the LIA extent slowed on many glaciers at the beginning of the 20th century, some of them even readvanced almost to the LIA extent. The 1930s and 1940s brought a marked loss of ice masses and were followed by a moderate retreat. Around 1970 the recession generally slowed. Some glaciers even advanced. The last decade was again characterized by a pronounced glacier recession on all tropical mountains which are under observation. The modern fluctuations of tropical glaciers are also quite synchronous to those of the glaciers in the mid-latitudes. A reduction in air humidity with all the consequent changes in energy and mass balance is suggested to be a major reason for the general recession of tropical glaciers since the end of LIA. The rise in air temperature explains only part of the glacier recession. The accelerated recession since the 1980s is most probably caused by increased air temperature and increased air humidity. Nevertheless, the knowledge of tropical glaciers is still scarce compared to those of the mid and high latitudes. This contribution reviews present knowledge of the fluctuations of tropical glaciers.