Harsh climate selects for small body size among Iceland ’ s Arctic foxes

and is responsible for much of the variability of weather in the North Atlantic region. NAO variation thus refl ects weather, including ambient temperature, precipitation, wind speed and direction, as well as the intensity, number, and track of storms throughout the North Atlantic region. Positive NAO leads to relatively strong westerly winds across the mid-latitudes of the Atlantic to Europe, resulting in cool, wet summers and mild, wet winters in Europe and cold, dry winters in Greenland. In contrast, when the NAO is negative, European winters are cold, while Greenland experiences milder winter temperatures. Th e relationship between NAO and temperature in Iceland resembles that for Greenland, but is weaker and diminishes from west to east (Hurrell and van Loon 1997, Hanna et al. 2004). Th e sub-polar gyre (SPG) is an ocean current carrying warm, subtropical waters into the north-eastern Atlantic, circulating northward and westward in a counterclockwise motion near Iceland and the southern tip of Greenland. Th e current loses heat to the atmosphere as it moves north, where it meets cold Arctic currents, thus aff ecting the climate of the entire North Atlantic region ( < www.nasa.gov/vision/ earth/environment/North_Atlantic.html > ). When the SPG index is high, the temperature and salinity of waters fl owing from the south across the Greenland – Scotland ridge on both sides of Iceland are relatively low, and vice versa for a low Ecography 39: 001–008, 2016 doi: 10.1111/ecog.01782 © 2016 Th e Authors. Ecography © 2016 Nordic Society Oikos Subject Editor: Zhiheng Wang. Editor-in-Chief: Miguel Ara ú jo. Accepted 14 February 2016