Glacier Mass Balance Changes Research Articles

Impact of Climate Change on North Cascade Alpine Glaciers, and Alpine Runoff

Analysis of key components of the alpine North Cascade hydrologic system indicate significant changes in glacier mass balance, terminus behavior, alpine snowpack, and alpine streamflow from 1950 to 2005. North Cascade glacier retreat is rapid and ubiquitous. All 47 monitored glaciers are currently undergoing a significant retreat and four of them have disappeared. Annual mass balance measured on ten glaciers, averaging 30–50 m in thickness, yields a mean cumulative annual balance for the 1984–2006 period of −12.4 m water equivalent (m we), a net loss of 14 m in glacier thickness and 20–40% loss of their total volume in two decades.The data indicate broad regional continuity in North Cascades glacial response to climate. The substantial negative annual balances have accompanied significant thinning in the accumulation zone of 75% of North Cascade glaciers monitored. This is indicative of glacier disequilibrium; a glacier in disequilibrium will not survive the current warmer climate trend. Alpine snowpack snow water equivalent (SWE) on April 1 has declined 25% since 1946 at five USDA Snow Course sites. This decline has occurred in spite of a slight increase in winter precipitation. The combination of a decline in winter snowpack and a 0.6° increase in ablation season temperature, during the 1946–2005 period in the North Cascades, has altered alpine streamflow in six North Cascade basins. Observed changes in streamflow are: increased winter streamflow, slightly declining spring streamflow and a 27% decline in summer streamflow. Only in the heavily glaciated Thunder Creek Basin (> 10% glaciated) has summer streamflow declined less than 10%; this is attributable to enhanced glacier melting.

Un service d’observation des glaciers des alpes françaises « glacioclim-alpes », pour quoi faire ?

Glaciers act as very good climate indicators, and the relationship they develop with climate can be exploited at 2 levels. First of all, changes in meteorological conditions are directly recorded in glacier mass balance changes (in the form of either winter precipitation or summer ablation). Therefore, from separately measuring these two terms, climatic trends can be inferred and corresponding results are all the better as mass balance series are spanning longer periods. These mass balance changes then later express under the form of fluctuations in glacier length and thickness and/or ice surface velocities. Measuring these changes is another means of inferring climate change, although the relationship is much more complex because of a time-lagging non-linear response due to complicated processes such as ice rheology or basal gliding which only a deterministic ice-flow model can capture. Due to this specificity and complexity of the dynamical response of glaciers, using these glacier changes for climate reconstructions will also require as long as possible measurement series. It is therefore in this context of a better understanding of climate through glacier change that the glacier survey network was initiated. Three main types of measurements are undertaken ; (i) mass balance measurements with both winter accumulation and summer ablation, (ii) glacier dynamical response to mass balance change in the form of thickness and length changes as well as surface velocity measurements and last (iii) measurements of local meteorology with the help of Automatic Weather Stations. This paper describes the structure and the context in which the survey network was initiated as well as all the ensuing measurements. Some scientific applications are then presented as the results of these observations like the significant changes in surface mass balance connected to the strong changes in radiative and turbulent heat fluxes at the surface of glaciers over the last decades, or the better understanding of ice dynamics from direct inspection of glacier dynamical changes or from using these latter changes for tuning, validating and exploiting the results of an ice flow model.

Response of Hofsjökull and southern Vatnajökull, Iceland, to climate change

(Possible changes in glacier mass balance are among the most important consequences of future climate change with both local and global implications, such as changes in the discharge of glacial rivers, changes in the vertical stratification in the upper layers of the Arctic Ocean, and a rise in global sea level. The response of the Hofsjökull and southern Vatnajökull ice caps in Iceland to climate change is analyzed with a vertically integrated, finite difference ice flow model coupled with a degree day mass balance model. Transient climate change simulations are forced with a climate change scenario for the Nordic countries, which for Iceland, specifies a warming rate of 0.15°C per decade in midsummer and 0.3°C per decade in midwinter, with a sinusoidal variation through the year starting from the baseline period 1981–2000. Precipitation is either held steady or is increased at 5% per °C of warming. Modeled ice volume is reduced by half within 100–150 years. About 2030, annual average runoff from the area that is presently covered by ice is projected to have increased by approximately 0.7 m yr−1 for Hofsjökull and by 1.4 m yr−1 for southern Vatnajökull. The sensitivity of the mass balance of the ice caps to climate change was found to be in the range 0.4–0.8 mw.e. yr−1 °C−1 for Hofsjökull and 0.8–1.3 mw.e. yr−1 °C−1 for southern Vatnajökull. The sensitivity remained within these ranges more than 150 years into the future.)

‘Little Ice Age’ proxy glacier mass balance records reconstructed from tree rings in the Mt Waddington area, British Columbia Coast Mountains, Canada

The intention of this research was to explore whether dendroclimatological relationships could be used to reconstruct long-term proxy records of ‘Little Ice Age’ glacier mass balance changes in the southern Coast Mountains of British Columbia. Tree-ring width chronologies from the Mt Waddington area were used in concert with historical glacier records to construct models spanning the past 450 years. The approach was to build models that were based on derived relationships between tree-ring growth and glacier mass balance: (1) warmer temperatures in the summer positively influence tree growth but are detrimental to glacier health; (2) colder temperatures during the winter and deeper snowpack have a negative impact on tree growth, whereas they are related to greater accumulation on the glacier during the winter season. Stepwise regression analyses were applied to tree-ring chronologies to predict glacier mass balance at local and regional scales. The models of net annual balance for the region (regional data set) show that periods of positive mass balance occurred in the AD 1750s, 1820s to 1830s and 1970s. Peaks of winter balance correspond closely to these periods, showing a sharp drop in winter mass balance towards the end of the nineteenth century. Wavelet analyses suggest that glacial mass balance regimes in the region respond synchronously to Pacific Ocean circulation systems such as the El Niño Southern Oscillation and the Pacific Decadal Oscillation.

Decadal variability in climate and glacier fluctuations on mt baker, washington, usa

Climate variability in the Pacific basin has been attributed to large‐scale oceanic‐atmospheric modulations (e.g. the El Niño‐Southern Oscillation (ENSO)) that dominate the weather of adjacent land areas. The Pacific Decadal Oscillation (PDO) and north Pacific index are thought to be indicators of modulations and events in the northeast Pacific. In this study we find that variations in the PDO are reflected in the terminus position of glaciers on Mt Baker, in the northern Cascade Range, Washington. The initiation of retreat and advance phases of six glaciers persisted for 20–30 years, which relate to PDO regime shifts. The result of this study agrees with previous studies that link glacier mass balance changes to local precipitation anomalies and processes in the Pacific. However, the use of mass balance changes and glacier terminus variation for identification of regime shifts in climate indices is complicated by the lack of standardized measuring techniques, differing response times of individual glaciers to changes in climate, geographic and morphometric factors, and the use of assorted climate indices with different domains and time‐scales in the Pacific for comparison.

Modelling changes in glacier mass balance that may occur as a result of climate changes

Projections of changes in glacier mass balance caused by climate changes involve modelling present mass balance in terms of climate and then perturbing the climate variables to calculate future mass balance. The simplest model involves linear regression of mass balance time series on temperature and precipitation data at stations close to the glacier but we prefer the degree‐day model. This model uses temperature and precipitation to calculate snow accumulation, snow and ice melting, and possible refreezing of meltwater at regular altitude intervals on a glacier. Model parameters are still somewhat uncertain and are established for individual glaciers by tuning the model mass balance as a function of altitude to fit observed data. The model has been applied to 37 glaciers in different parts of the world so far and some details are given for Storglaciären to illustrate the approach. The sensitivity of modelled mass balance to a +1°C temperature increase shows a wide range for the 37 glaciers from about 0.1 to 1.3 m water a−1 . Sub‐polar glaciers have lower temperature sensitivities, and maritime and tropical glaciers have higher sensitivities.

Modelling Changes in Glacier Mass Balance that may Occur as a Result of Climate Changes

Modelling Changes in Glacier Mass Balance that may Occur as a Result of Climate Changes

Slopes of glacier ELAs in the Southern Alps of New Zealand in relation to atmospheric circulation patterns

The links between climate and glaciers of the Southern Alps are investigated by examining the relationships between atmospheric circulation and glacier mass balance changes, as measured by end-of-summer snowlines (ELAs) over a 21-year period on 48 index glaciers. Trend surfaces are fitted to the ELAs data for each mass balance year, and the elevation and slope of each surface is computed. These are compared to atmospheric pressure anomaly maps generated for the southwest Pacific from long-period climate station data. The results show that atmospheric circulation patterns exert a strong control on elevation and slope of the trend surfaces. A simple “sloping roof” model is suggested to represent the ELAs surface, with its tilt across the Southern Alps varying from year to year, depending upon the nature of the atmospheric circulation. Steeper sloping trend surfaces across the Southern Alps are associated with anomalous southwest to westerly flow, whereas less steep slopes are associated with anomalous airflow from the south, southeast, and easterly directions.

Holocene glacier and climate fluctuations on Franz Josef Land, Arctic Russia, 80°N

Fluctuations in glacier extent provide the first comprehensive record of Holocene paleoclimate for Franz Josef Land. Glacier fluctuations were constrained using 45 14C ages from 16 glacier margins. Many glaciers were behind present margins before 9.4 kyr, possibly as early as 10.3 kyr, and probably remained so until at least 4.4 kyr (where kyr= 14C yr B.P./1000). Subsequently, glaciers expanded, probably reaching present margins before 3.2 kyr, but certainly by 2 kyr. A prominent Neoglacial advance occurred ca. 1 kyr, and was followed by ‘Little Ice Age’ advances, including one in the middle 1600s A.D. Glaciers were larger than present at the turn of the century, followed by widespread retreat soon after. The Holocene glacier record closely mimics that of Svalbard, 500 to 1000 km to the west, suggesting similar glacier mass balance changes over a broad region of the Eurasian Arctia. Independent paleoclimate evidence from Svalbard indicates higher-than-present summer air temperatures during the early to middle Holocene, when glaciers were behind present margins, followed by generally cooler summer conditions and intermittent glacier advances and retreats. Holocene glacier variations were probably more influenced by summer temperature than winter precipitation.

Detection of abrupt changes in glacier mass balance in the Tien Shan Mountains

AbstractBased on glacier mass-balance records collected, compiled and published by the World Glacier Monitoring Service (WGMS), an attempt is made here to determine whether there were abrupt decadal-scale changes in annual balance on glaciers in the Tien Shan Mountains. There appears to have been an abrupt change in the mid-1970s; two-thirds of the change was caused by an increase in annual ablation and the other one-third by a decrease in the annual accumulation. Thus, the change was caused mainly by a summer-temperature increase, supplemented by a decrease in annual snowfall. Climate records suggest that this event, in effect, is in response to a shift hi the background state of the coupled Ocean -atmosphere system over the Tropical Pacific during the mid-1970s.

Detection of abrupt changes in glacier mass balance in the Tien Shan Mountains

AbstractBased on glacier mass-balance records collected, compiled and published by the World Glacier Monitoring Service (WGMS), an attempt is made here to determine whether there were abrupt decadal-scale changes in annual balance on glaciers in the Tien Shan Mountains. There appears to have been an abrupt change in the mid-1970s; two-thirds of the change was caused by an increase in annual ablation and the other one-third by a decrease in the annual accumulation. Thus, the change was caused mainly by a summer-temperature increase, supplemented by a decrease in annual snowfall. Climate records suggest that this event, in effect, is in response to a shift hi the background state of the coupled Ocean -atmosphere system over the Tropical Pacific during the mid-1970s.

Predicted response of Storglaciären, Sweden, to climatic warming

A time-dependent model of glacier flow was used to predict the response of Storglaciären, a small valley glacier in northern Sweden, to different warming scenarios by imposing two possible climatic forcings: one in which temperature alone increases (T model), and one in which both temperature and precipitation increase (TP model). A range of possible changes in temperature and/or precipitation was related to changes in glacier mass balance through a multiple linear correlation of mean specific net balance with mean summer temperature and mean specific winter balance. The T model was run with mass-balance perturbations in the form of linear increases from the recent (1980–89) mean summer temperature of 1, 2 and 4°C over the next 100 years. Perturbations for the TP model also used linear increases in precipitation of 10, 20 and 50% over current mean winter values in addition to increases in temperature. Results of the modeling suggest that initial changes in the glacier‘s profile due to increases in temperature, or in both temperature and precipitation, are of comparable magnitude to those that might be expected as the glacier completes its response under the existing climate. Changes in the glacier‘s surface profile and terminus position that can, with some certainty, be attributed to climatic warming may only become apparent several decades after warming has begun.

Predicted response of Storglaciären, Sweden, to climatic warming

A time-dependent model of glacier flow was used to predict the response of Storglaciären, a small valley glacier in northern Sweden, to different warming scenarios by imposing two possible climatic forcings: one in which temperature alone increases (T model), and one in which both temperature and precipitation increase (TP model). A range of possible changes in temperature and/or precipitation was related to changes in glacier mass balance through a multiple linear correlation of mean specific net balance with mean summer temperature and mean specific winter balance. The T model was run with mass-balance perturbations in the form of linear increases from the recent (1980–89) mean summer temperature of 1, 2 and 4°C over the next 100 years. Perturbations for the TP model also used linear increases in precipitation of 10, 20 and 50% over current mean winter values in addition to increases in temperature.Results of the modeling suggest that initial changes in the glacier‘s profile due to increases in temperature, or in both temperature and precipitation, are of comparable magnitude to those that might be expected as the glacier completes its response under the existing climate. Changes in the glacier‘s surface profile and terminus position that can, with some certainty, be attributed to climatic warming may only become apparent several decades after warming has begun.

Predictions of changes of glacier mass balance in the Nepal Himalaya and Tibetan Plateau: a case study of air temperature increase for three glaciers

Annual mass exchange differs between maritime and continental glaciers. A common characteristic of these glaciers in Asian high-mountain areas is that most of the annual accumulation occurs in summer. Since variations in mass balance of a summer-accumulation type of glacier are quite sensitive to variations in summer air temperature, shrinkages of such glaciers due to climate warming are predicted by the use of simplified experimental relations between air temperature and mass balance, disregarding variation of other climatic variables such as cloudiness and precipitation. The results predict that both small and large maritime glaciers are more sensitive to warming than a continental ice cap. A small glacier would disappear in a few decades if the air temperature persisted a few degrees above that of an equilibrium state of mass balance.

Predictions of changes of glacier mass balance in the Nepal Himalaya and Tibetan Plateau: a case study of air temperature increase for three glaciers

Annual mass exchange differs between maritime and continental glaciers. A common characteristic of these glaciers in Asian high-mountain areas is that most of the annual accumulation occurs in summer. Since variations in mass balance of a summer-accumulation type of glacier are quite sensitive to variations in summer air temperature, shrinkages of such glaciers due to climate warming are predicted by the use of simplified experimental relations between air temperature and mass balance, disregarding variation of other climatic variables such as cloudiness and precipitation. The results predict that both small and large maritime glaciers are more sensitive to warming than a continental ice cap. A small glacier would disappear in a few decades if the air temperature persisted a few degrees above that of an equilibrium state of mass balance.

Comparison of in situ and landsat derived reflectance of Alaskan Glaciers

Calculation of snow and ice albedo is necessary for developing physically realistic simulations of the Earth's climate using general circulation models, and useful for analysis of glacier mass balance change using remote sensing. Reflectances calculated from TM data and corrected for atmospheric effects correspond with in situ measured reflectances in the nadir-viewing mode, and are shown to be related to a glacier's mass balance if measured over a period of years. A reflectance of 0.895 for a test site in the Wrangell Mountains, Alaska, was calculated from TM Band 4 (0.76–0.90 μm) data and corrected for atmospheric effects. This value was comparable to the in situ reflectance of 0.90 measured in the same 0.76–0.90 μm wavelength region. For the same site, a reflectance value of 0.79 derived from integrating over most (0.40–3.0 μm) of the reflective portion of the electromagnetic spectrum was quite different from the integrated reflectance of 0.95 calculated for the spectral range 0.40–1.0 μm. This demonstrates the importance of using the full reflective energy spectrum for calculating the albedo of snow, and for obtaining a meaningful computation of a glacier's energy and mass balance change.