Climate change and Northern Hemisphere lake and river ice phenology from 1931–2005

Abstract. At high latitudes and altitudes one of the main controls on hydrological biogeochemical processes is breakup freeze-up lake river ice. This study uses 3510 time series from across 678 Northern Hemisphere lakes rivers to explore historical patterns in ice phenology five overlapping periods (1931–1960, 1946–1975, 1961–1990, 1976–2005, 1931–2005). These show that number annual open-water days increased by 0.63 d per decade 1931–2005 Hemisphere, with trends for and, a lesser extent, closely correlating regionally averaged temperature. Breakup display spatiotemporally complex evolution reveal considerable caveats interpreting implications changes at sites may only have or data, rather than both. results provide an important contribution showing regional variation through can be hidden longer-term trends. The 30-year also evidence acceleration warming time. Understanding both long- short-term timescales will determining causes this change, underlying associated it, wider climatological significance as global temperatures rise.