Transition Zones between the Earth System Components

Abstract:

The concept of transition zones has been applied to many fields of Earth science. A transition zone is defined as a domain where the state within an Earth system component changes gradually. Transition zones exist between, for example, the lower and upper mantles, coastal deep and shelf water, dry and humid climate regimes, the convective and stratiform areas of a squall line, and regions with different dominant biotas. The concept of transition zones can be applied to expand the conventional definitions of the interfaces between the Earth system components. For example, the air-sea transition zone includes the upper ocean, air-sea interface, and the atmospheric marine boundary layer as a single identify instead of a sum of the three different parts. Similarly, the land-air transition zone includes upper-layer and surface soil, ground and surface water, vegetation, and the atmospheric boundary layer. The coastal transition zone can be extended from its traditional definition to include the deep and shallow seas, estuaries, wet and dry lands, and the atmosphere boundary layer that connects all of them. Using transition zones in place of interfaces would help advance studies of interactions and coupling of the Earth system components. New challenges of observing and modeling the transition zones of the Earth system components need to be met with creative thinking and novel technologies.