Land Use Change and Modification of Near-Surface Thermal Records in the Northern Great Plains

The North American Great Plains have experienced a rapid overturning of natural grasslands to agricultural land use over the last century. Moreover, in some areas more than 80% of the land use has changed from dry land to irrigated agriculture during the second half of the twentieth century. It is speculated that these changes have modified near-surface atmospheric condition and our modeling study seems to support this. To identify changes in land surface- atmospheric modifications we have applied a soil moistureenergy balance model at three locations in Nebraska: Mead, York, and McCook. The model was applied for three land uses (natural grass, rain-fed maize, and irrigated maize) at each of these locations. These locations represent the eastto- west hydroclimatic gradient of the Great Plains. We have found from the model applications that land use change has modified nearsurface soil moisture amount and evapotranspiration (ET; thus, energy balance) in the northern Great Plains. For example, for McCook, Nebraska, the ET from irrigated maize is nearly 36% higher than natural grass. It is expected that a modification of energy balance of this magnitude would have an imprint on surface temperature records. Thus, a further investigation of long-term temperature record was undertaken