The intensification of Arctic warming as a result of CO2 physiological forcing

Abstract

There are various ways in which plants sensitively respond to changes in atmospheric CO2 concentration. The closing of the stomata is one of the main physiological responses to increases in atmospheric CO2 concentration, leading to a reduction in plant water loss. This response has the potential to trigger changes in the climate system by regulating the hydrological cycle and surface energy budgets–a phenomenon known as CO2 physiological forcing. Here it is suggested that physiological forcing of pan-Arctic vegetation remotely influences changes in the Arctic climate. Surface warming occurs at mid-to-high latitudes, especially in boreal summer, due to a reduction in evaporative cooling and an increase in sensible heat flux as a result of plants acclimatizing to increases in CO2 concentration. The resulting reduction in cloud fraction enhances net shortwave absorption and additionally heats the surface. This excess heat energy over the continents is transported to the Arctic through the process of atmospheric circulation, thereby leading to accelerated Arctic warming. The Arctic warming is further amplified by feedbacks related to sea-ice loss and it has been found that this physiological forcing effect amplifies the warming of the Arctic by around 10% that of radiative forcing. Our analysis suggests that the presence of vegetation at high latitude considerably enhances Arctic amplification via remote and time-delayed CO2 physiological forcing processes.