New data, new techniques and new challenges for updating the state of Svalbard glaciers

This is chapter 4 of the State of Environmental Science in Svalbard (SESS) report 2019 (https://sios-svalbard.org/SESS_Issue2).

Glacier mass balance is the budget between snow accumulation and melting of snow and ice. Where glaciers terminate in the ocean, calving of icebergs constitutes an additional mechanism of mass loss, though it is more difficult to assess than snow accumulation and surface melting. The SvalGlac report reviews new technologies and new data that have become available in the past 20 years to update previous assessments. We find that glaciers all over Svalbard are losing mass, with rates depending on geographical location and glacier size. Smaller glaciers in southern Spitsbergen experience highest rates of mass loss while large ice caps in Northeast Svalbard are closer to a balance situation. However, variations from year to year are large and long-term observations are needed to recognise trends. These spatial patterns and temporal evolution are also supported by modelling studies that calculate surface mass balance based on meteorological data, and by studies applying satellite remote sensing.

The only available estimate of calving needs updating, especially with regard to year-to-year and seasonal variations. Several large surges have occurred in the past few years, strongly influencing the amount of ice discharged into the ocean. A glacier surge is a switch from a slow to fast flowing mode, sometimes happening periodically. The mechanisms responsible for surges are not well understood but several Svalbard-based studies shed new light on these processes.

The most important gaps are:

• our incomplete understanding of surging, both the process itself and its implications for Svalbard glacier mass balance

• incomplete basic data coverage for quantification of calving and

• limited information about glacier mass balance and meltwater runoff in a future climate.