Two decades of snow pit measurements in Sodankylä, Finland

We present a 20-year timeseries of key snow properties measured in Sodankylä, northern Finland. Systematic snow pit observations began in 2006, and the range of measured variables and instruments has expanded substantially over time. Initially, observations included snow depth, stratigraphy, grain size, and temperature, recorded twice per week at a forest opening site. Snow water equivalent (SWE) measurements were added in 2007, density profiles and liquid water content in 2009, and specific surface area (SSA) measurements in 2012. Since 2010, snow pit observations have been conducted once per week.

The monitored locations have varied over the years. A forest opening site was observed from 2006 to 2018, a wetland site from 2009 to 2015 and again from 2019 onward, and a forest site has been included since 2018. Additional snow pits were dug at Lake Orajärvi between 2009 and 2014. Currently, routine observations are carried out at two sites: a wetland and a forest.

The present snow pit protocol includes definition of stratigraphy, a temperature profile measured every 10 cm, and estimation of grain size and grain type, complemented by macrophotography of grain samples from each layer. Density measurements are performed at the surface and at 5 cm vertical intervals using a rectangular cutter. When snow is wet, liquid water content is measured with a WISe instrument at the same heights as the density samples. SSA is measured using InfraSnow for the surface and ice layers, while other layers are measured with IceCube. For thicker layers, IceCube samples are taken every 5 cm. Penetration resistance is measured with SnowScope. Finally, bulk SWE is measured using a snow tube, and snow depth is measured at three points around each pit.

This 20-year dataset provides a unique opportunity to examine long-term changes in snowpack structure and properties, and it illustrates the impacts of a changing climate in snow conditions in northern Finland.