Snow-climate feedback

Results are shown in Figure 5 b. At the end of April, the ice thickness is 37 cm with the cold scenario and 58 cm with the warm scenario, so that changes in snow kj more than offset atmospheric warming. This increased sea ice thickness clearly constitutes a negative snow-climate feedback loop that deserves consideration in climate models. Of course, this fast ice example cannot be taken at face value, as sea ice growth is much more complex than described here. Other effects must be taken into account such as convection in the water that depend on growth rate, lateral heat fluxes in the ice and turbulent fluxes at the snow-air and sea-ice interfaces. " However, this example does illustrate the importance of one factor, the heat conductivity of snow, that will be affected by climate change. 

Five components of the hydrosphere play major roles in climate feedbacks - atmospheric moisture, clouds, snow and ice, land surface, and oceans. Changes to the hydrologic cycle, among other things, as a result of altered climate conditions are then referred to as responses. Interactions with climate can best be explored by examirung potential response to a climate perturbation, in this case, predicted global warming. 

There is a potentially important influence of ice and snow at the surface, for ice and snow have high albedos. Ice-albedo feedback may increase the sensitivity of the climate system. That is, low temperature causes more ice and a higher albedo, allowing less absorption of sunlight and therefore causing a still lower temperature. This temperature effect is included by... 

The climatic system involves numerous factors that intensify climatic changes with minimum forcings. The withering or death of plants, for example, may cause a decrease in evapotranspiration and hence lead to precipitation attenuation, which may further increase drought conditions. In cold-climate regions snow cover formation is accompanied by a strong increase in albedo, which favors further cooling (the so-called albedo effect ). Substantial climatic feedbacks are associated with the dynamics of thermohaline circulation. 

Jacobson MZ (2004b) The climate response of fossil-fuel and biofuel soot, accounting for soot s feedback to snow and sea ice albedo and emissivity. J Geophys Res 109 021201. doi 10.1029/ 2004JD004945... 

Snowpack chemical emissions include oxidants and aerosol precursors, that also interact with climate. Oxidants determine the lifetime of greenhouse gases and aerosols impact the atmospheric radiation budget. If snowpack chemical emissions are determined by climate, feedback loops involving snow chemistry also need to be studied to assess the extent of climate change in snow-covered regions. 

Several models have quantified the climate warming-snow albedo feedbacks caused by an increase in soot in polar snow. Hansen and Nazarenkofound that predicted soot increases would decrease the spectrally-averaged albedo by 1.5%. This results in a 1.5 W.m " forcing at high latitude, producing a warming between 1 and 2 °C. 

Other factors may further complicate the climate-SSA feedback. Albedo is mostly determined by surface snow, although underlying layers also have an effect." A critical factor to determine snow SSA is the age of the surface snow, and hence the time elapsed between snow falls. Thus, the time distribution of precipitation events, as well as that of wind storms, is an extra factor to consider when modeling the warming-albedo feedback. 

Interactions that can be described as a theoretical concept of a feedback mechanism in which the interacting elements are the areal extent of polar ice and snow cover, the albedo of the polar region (dependent on areal extent of ice and snow), absorption of solar radiation (dependent on the albedo), temperature (dependent on the absorption of solar radiation) and the area of ice and snow cover (dependent on temperature). Less snowfall would mean more absorption of solar radiation, therefore a surface warming would occur. Climate modeling studies indicate an amplification effect (i.e., positive feedback) of the ice and snow-albedo feedback on increased surface air temperatures caused by increases in the atmospheric concentration of carbon dioxide, ice cover... 

For weather prediction in the polar areas, it is important to take into account the effects of sea ice. Approximately 2% of the total water on the earth is stored in the form of ice in polar areas and glaciers. Sea ice accounts for nearly two-thirds of the earth s ice cover in areal extent. Sea ice plays the major role of controlling the exchange of heat, water vapor, and momentum between sea and air in the polar regions. Ice cuts off heat and water vapor transport from the ocean to the atmosphere and increases the albedo. Thus, similar to snow cover over land, sea ice contributes to cooling over the ice surface, which, in turn, tends to thicken the ice— a positive climatic feedback. 

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