Pan-Arctic linkages between snow accumulation and growing-season air temperature, soil moisture and vegetation

Arctic field studies have indicated that the air tem- perature, soil moisture and vegetation at a site influence the quantity of snow accumulated, and that snow accumulation can alter growing-season soil moisture and vegetation. Cli- mate change is predicted to bring about warmer air tempera- tures, greater snow accumulation and northward movements of the shrub and tree lines. Understanding the responses of northern environments to changes in snow and growing- season land surface characteristics requires: (1) insights into the present-day linkages between snow and growing-season land surface characteristics; and (2) the ability to continue to monitor these associations over time across the vast pan- Arctic. The objective of this study was therefore to examine the pan-Arctic (north of 60 N) linkages between two tem- porally distinct data products created from AMSR-E satel- lite passive microwave observations: GlobSnow snow wa- ter equivalent (SWE), and NTSG growing-season AMSR- E Land Parameters (air temperature, soil moisture and veg- etation transmissivity). Due to the complex and intercon- nected nature of processes determining snow and growing- season land surface characteristics, these associations were analyzed using the modern nonparametric technique of al- ternating conditional expectations (ACE), as this approach does not impose a predefined analytic form. Findings indi- cate that regions with lower vegetation transmissivity (more biomass) at the start and end of the growing season tend to accumulate less snow at the start and end of the snow sea- son, possibly due to interception and sublimation. Warmer air temperatures at the start and end of the growing season were associated with diminished snow accumulation at the start and end of the snow season. High latitude sites with warmer mean annual growing-season temperatures tended to accu- mulate more snow, probably due to the greater availability of water vapor for snow season precipitation at warmer loca- tions. Regions with drier soils preceding snow onset tended to accumulate greater quantities of snow, likely because drier soils freeze faster and more thoroughly than wetter soils. Un- derstanding and continuing to monitor these linkages at the regional scale using the ACE approach can allow insights to be gained into the complex response of Arctic ecosystems to climate-driven shifts in air temperature, vegetation, soil moisture and snow accumulation.