Subsurface urban heat islands

Temperatures in shallow urban ground are typically elevated. They manifest as subsurface urban heat islands (SubSUHIs) where most extreme temperature anomalies are primarily observed near underground structures (e.g. parking garages). Here annual mean temperatures are often > 6 K warmer than the rural surrounding. However, on a city wide scale SubSUHIs are primarily fueled by elevated ground surface temperatures - urban heat islands at the surface and in the subsurface are coupled through conductive heat transport. Using statistical and spatial analytical heat flux models we are able to quantify the annual heat input of dominate heat sources and discuss its potential for sustainable geothermal heat recycling. Extracting this anthropogenically originated energy could also keep groundwater temperatures from rising further.