This document details the monitoring program run by Tarfala Research Station (TRS) by providing a brief background to the station and activities there as well as a scientific rationale for the measurements. Most of the measurements made at Tarfala Research Station are strongly coupled to issues relating to global climate and environmental change. Much of the data is also important for basic research and development of new methods for monitoring.


Being the origin of activities at Tarfala, the mass balance monitoring program of Storglaciären has always been at the centre of the activities at Tarfala Research Station. The mass balance series is now the world's longest continuous series of measurements using the so-called Scandinavian method, which involves measuring both the total mass added in the form of snow during winter and the total mass lost through melt during the following summer, thus defining a mass balance year and the net change during this year (Figure 3). The method used by Tarfala on Storglaciären was largely developed as experience was gained throughout the years and is now the standard method of mass balance measurements used in most monitoring systems around the world, albeit with modifications for local conditions.

Glacier mass balance
Documented glacier changes are key elements within strategies for early detection of global climate change. Small glaciers and ice caps (defined by e.g. the Intergovernmental Panel on Climate Change, IPCC, as all masses of ice outside of Antarctic and Greenland ice sheets) constitute a large source of fresh water that, if released from storage, affects the environment in two principal ways, by contributing to sea-level change and by affecting runoff in rivers of the terrestrial environment. The glaciers also constitute important objects for tourism and contributing to the natural environment in mountainous regions. Glaciers are inherently effects of climate since their existence is determined by the balance between mass gains through e.g. snowfall (on glaciers in the Tarfala monitoring program mainly winter snow) and mass losses through e.g. melting (manly summer melting in the Tarfala case). Glacier mass balance monitoring, thus provide year by year updates to the state of glaciers as well as contribute to understanding their long-term contribution to e.g. sea-level change.
- extensive glacier mass balance and flow studies within major climatic zones for improved process understanding and calibration of numerical models;
- determination of regional glacier volume change within major mountain systems using cost-saving methodologies;
- long-term observations of glacier length change data within major mountain ranges for assessing the representativity of mass balance and volume change measurement;
- glacier inventories repeated at time intervals of a few decades by using satellite remote sensing.
The primary reason for recording climate parameters at Tarfala Research Station and elsewhere in the mountains has been to provide a climatological framework for the mass balance measurements. As our understanding of the climate forcing on glacier mass balance has developed, the measurements of climate parameters have become more advanced.
Measurements of glacier mass balance is labor intensive and also involves logistical problems since successful measurements involve two visits annually to each glacier by as much as four persons in order to collect reliable data. Since glacier volume change essentially involves both changes in surface elevation and a change in glacier surface area, both can be used as a proxy measurement of the true volume change. This is however not straight forward since the change in surface typically occurs with some delay once the volume has changed, that is to say the surface elevation changes more rapidly than the surface area. The surface area, however, is a much easier quantity to measure (represented by the terminus of the glacier). For valley glaciers, the most common type of glacier in the Scandinavian mountains, the surface area change is equivalent to a change in length of the glacier. Traditionally this has been accomplished by traditional surveying by either triangulation methods or, more recently, differential global positioning systems (dGPS) of the terminus of glaciers. Surface elevation changes can also be surveyed but involve additional difficulties, including the safety aspects of traveling on the glacier surface, that makes area measurements much more cost effective. It seems likely that satellite measurements of surface elevation changes may become available in the future but presently area measurements seem to be the only measurements that can be made with sufficient accuracy. Satellite measurements of glacier area have also become available and are used to provide regional inventories. The resolution of satellite images, and the difficulties involved in defining the actual glacier area from such images (e.g. due to marginal snow fields that obscure the true glacier outline), enables monitoring of areal changes with time resolution of 5-10 years, depending on the rate of change in area of the individual glaciers. Measurements of changes in glacier surface area thus contribute important information that provides regional estimates of volume change and also provides a wider framework for interpreting the detailed volume change measurements provided by the glacier mass balance monitoring program. Glacier terminus measurements thus constitute the end member in a three-pronged approach including glacier mass balance measurements on the reference glacier, supporting glaciers.
One of the main effects of climate change on the mountain environment involves a redistribution of runoff by changing the length of the warm and cold seasons as well as possibly changing the amount of precipitation. Redistribution thus occurs because snow fall is replaced by rainfall and because storage characteristics of the catchment may change. In the cases where the catchments harbor glaciers, changes in both the average discharge and the variability (amplitude) of discharge variations can be expected. Since very few catchment located in alpine mountainous environments are gauged, combined records of snow accumulation and melt and runoff are very rare. Through the construction of a permanent gauging station, Rännan, in the Tarfala valley in response to the International Hydrological Decade (IHD, 1965-1975) and the participation of the Tarfala Research Station in the IHD activities, Tarfala constitutes the only gauged alpine catchment in Sweden . In addition, the IHD activities provided base line data with which continued monitoring data can be compared.
Permafrost (permanently frozen ground) is a core feature of the arctic and sub-arctic environments. Since permafrost owes its existence to a negative energy balance at the Earth's surface, changes in the energy balance also greatly affects the permafrost, through more extensive thawing of the surface and in a longer perspective changing the geographical area harboring permafrost. The ongoing global climate changes already visibly affects areas with permafrost such as the Alps region where thawed soils in high mountains are mobilized resulting in increased hazards for structural damage and loss of life, as well as causing permanent change in the natural environment essential for e.g. tourism and agriculture.
- The establishment of a European Permafrost Monitoring Network by drilling a series of 7 instrumented boreholes forming a north-south transect from Svalbard to the Sierra Nevada .
- Developing new methods for geophysical mapping of ice-rich frozen ground
- Integration of field-based microclimate measurements to calibrate physically-based numerical modelling of the distribution of thermally sensitive mountain permafrost.
- New applications of geotechnical centrifuge modelling to investigate the potential instability of thawing ice-rich soil and rock slopes.
A critical and on-going outcome of the PACE project was the permafrost borehole monitoring network, consisting of a series of 100 m deep instrumented permafrost boreholes, providing the major European contribution to the Global Climate Observing System (GCOS) Global Terrestrial Network for Permafrost (GTN-P). There remains a major need to coordinate data collection, and to establish further international collaboration so that similar systems, for instance in the Ural Mountains and in arctic regions, can be established to provide data for inter-regional and global synthesis. Associated with this is a requirement for international networking programs to coordinate regional monitoring systems, interface these with global data banks such as GTN-P, and provide large-scale analysis of regional patterns of climatically forced change.
The continuous measurement of ground temperature through the 100 m bore hole is the main thrust of permafrost monitoring at Tarfala. Data indicate a 100 m temperature of -2.7°C and a possible permafrost depth of ~300 m. Through the connection to global observation networks, data is made available to researchers and contributing to our increased understanding of the effects of global climate change on the cryosphere.
Concluding remarks
The monitoring performed by Tarfala Research Station comprises glacier mass balance and volume change, alpine meteorology, alpine hydrology, and permafrost. This program constitutes a well balanced program for monitoring of central themes of the alpine environment. It is, however, obvious that additional types of monitoring measurements such as geochemical (e.g. pollutants and nutrients) variations and content and vegetation changes may be areas of expansion in the future. This will involve expanding the support basis for Tarfala in order to design and maintain such monitoring systems.
Acknowledgements
This document has been assembled and reviewed by the staff and researchers associated with Tarfala Research Station (Peter Jansson, Gunhild Rosqvist, Per Holmlund)