Areas of the Arctic are browning as the result of extreme weather events, which are becoming more frequent in the Arctic as the climate warms. A sudden period of warmth in the middle of winter tricks the plants into thinking it’s spring, so they burst bud early and lose their cold hardiness, leaving them unprepared for a return to normal cold winter temperatures. The plant die-back that follows the events of this ‘extreme winter warming’ also appear to be significantly reducing the ability of Arctic ecosystems to help combat climate change.
Ground that remains at or below freezing for at least two consecutive years. Permafrost often contains ancient frozen plant remains. When the ground thaws and the plants rot, it can cause very large emissions of greenhouse gases CO2 and methane.
Global warming thaws frozen land, which in turn emits gases that enhance warming.
Source of information about permafrost in the Nordics:
Polar low are small, intense low-pressure systems which form in the winter over Arctic waters. With a diameter of 200-600 kilometres, they resemble tropical cyclones but are smaller in extent and intensity. Weather conditions can shift from calm to storm in minutes with Polar lows. That means people must be particularly alert to such systems.
A proxy is a way to indirectly measure aspects of climate. Biological or physical records from ice cores, tree rings, and soil boreholes are good examples of proxy data