The Role of Climate and Land Use in the Changes in Surface Albedo Prior to Snow Melt and the Timing of Melt Season of Seasonal Snow in Northern Land Areas of 40°N–80°N during 1982–2015

Kati Anttila,Panu Lahtinen,Terhikki Manninen,Aku Riihelä,Emmihenna Jääskeläinen

doi:10.3390/rs10101619

Abstract

The rapid warming of the Northern Hemisphere high latitudes and the observed changes in boreal forest areas affect the global surface albedo and climate. This study looks at the trends in the timing of the snow melt season as well as the albedo levels before and after the melt season in Northern Hemisphere land areas between 40°N and 80°N over the years 1982 to 2015. The analysis is based on optical satellite data from the Advanced Very High Resolution Radiometer (AVHRR). The results show that the changes in surface albedo already begin before the start of the melt season. These albedo changes are significant (the mean of absolute change is 4.4 albedo percentage units per 34 years). The largest absolute changes in pre-melt-season albedo are concentrated in areas of the boreal forest, while the pre-melt albedo of tundra remains unchanged. Trends in melt season timing are consistent over large areas. The mean of absolute change of start date of melt season is 11.2 days per 34 years, 10.6 days for end date of melt season and 14.8 days for length of melt season. The changes result in longer and shorter melt seasons, as well as changed timing of the melt, depending on the area. The albedo levels preceding the onset of melt and start of the melt season correlate with climatic parameters (air temperature, precipitation, wind speed). The changes in albedo are more closely linked to changes in vegetation, whereas the changes in melt season timing are linked to changes in climate.

Highlights

Climate change over the Northern Hemisphere high latitudes and boreal forest zone has affected the snow and vegetation cover and, the surface albedo [1,2,3,4,5,6,7,8,9,10,11,12]
The snow cover extent has decreased especially significantly in the spring [3,5,7], and the surface albedo during the melt season months has decreased, largely due to a decline in the area covered by snow [10]
This paper presents a study of the changes in the surface albedo of the land areas of the Northern Hemisphere between latitudes 40◦N and 80◦N prior to the melt season

Summary

Introduction

Climate change over the Northern Hemisphere high latitudes and boreal forest zone has affected the snow and vegetation cover and, the surface albedo [1,2,3,4,5,6,7,8,9,10,11,12]. The decreasing trends for mean air temperature before the melt onset in the Central Siberian Plain (Figure 7a, Table 2) show similar spatial patterns as the melt season timing parameters This can be explained by the fact that the air temperatures prior to melt are not derived from the same time of year, but change together with the start date of melt. Using the climatic data from ERA-Interim, three parameters (mean air temperature, mean wind speed and accumulated precipitation) are required to explain the changes in the start date of melt, giving a mean R2 value of 0.65 for the whole study area (Figure 8).

Findings

Discussion

Conclusions