Lecture 4: Land Surface and Cryosphere (Outline)

Climate Roles

Surface Energy Balance

Surface Water Balance

Sea Ice

Land Ice

Climate Roles of Land Surface

greenhouse gas emissions

      è affects global energy and biogeochemical cycles

creation of aerosols

      è affects global energy and water cycles

surface reflectivity (albedo)

      è affects global energy cycle

impacts on surface hydrology

       è affect global water cycle

Land Surface Properties

Vegetation Properties

       Type and density

Soil Properties

       Depth and physical properties

      (e.g., moisture)

Characteristics of Vegetation Canopy

Typical Height

Leaf Area Index (LAI)

Leaf area index (LAI) is ratio of the total area of all leaves (one-side) on a plant to the area of ground covered by the plant.

It defines the area that interacts with solar radiation and that is responsible for carbon absorption and exchange with the atmosphere.

Soil Moisture Content

Cryosphere

Why is Ice Important to Climate?

Surface ice of any depth is a much more effective reflector of solar radiation than the underlying surface.

Sea ice is a good insulator and allows air temperature to be very different from that of the seawater under the ice.

At present, year-round ice covers 11% of the land area and 7% of the world ocean.

Sea Ice

One major climate effect of sea ice is to seal off the underlying ocean from interaction with the atmosphere.

Without an sea ice cover, high-latitude oceans transfers large amount of heat to the atmosphere, especially in winter.

With an sea ice cover, the heat flux into the atmosphere is stopped. In addition, the ice surface absorbs little incoming solar radiation. Winter air temperature can cool 30°C or more near a sea-ice cover.

Land Ice

Glacial Ice

Ice cores retrieve climate records extending back thousands of years in small mountain glaciers to as much as hundreds of thousands of years in continental sized ice sheets.

The antarctic ice sheet has layers that extend back over 400,000 years.

The Greenland ice sheet has layers that extended back 100,000 years.

Ice and Sea Level

The Antarctic Ice Sheet holds the equivalent in seawater of 66 meters of global sea level.

The Greenland Ice Sheet holds the equivalent of 6 meters of global seawater.

Global Warming and Sea-Level Change

Sea Level Rise .vs. Sea Floor Sink

Interactions between Ice and Ocean

This hypothesis argues that millennial oscillations were produced by the internal interactions among various components of the climate system.

One most likely internal interaction is the one associated with the deep-water formation in the North Atlantic.

Millennial oscillations can be produced from changes in northward flow of warm, salty surface water along the conveyor belt.

Stronger conveyor flow releases heat that melts ice and lowers the salinity of the North Atlantic, eventually slowing or stopping the formation of deep water.

Weaker flow then causes salinity to rise, completing the cycle.


	Climate Roles
	Surface Energy Balance
	Surface Water Balance
	Sea Ice
	Land Ice


	greenhouse gas emissions
	è affects global energy and biogeochemical cycles
	creation of aerosols
	è affects global energy and water cycles
	surface reflectivity (albedo)
	è affects global energy cycle
	impacts on surface hydrology
	è affect global water cycle


	Vegetation Properties
	Type and density
	Soil Properties
	Depth and physical properties
	(e.g., moisture)


	Typical Height

	Leaf Area Index (LAI)
	Leaf area index (LAI) is ratio of the total area of all leaves (one-side) on a plant to the area of ground covered by the plant.

	It defines the area that interacts with solar radiation and that is responsible for carbon absorption and exchange with the atmosphere.


	Surface ice of any depth is a much more effective reflector of solar radiation than the underlying surface.
	Sea ice is a good insulator and allows air temperature to be very different from that of the seawater under the ice.
	At present, year-round ice covers 11% of the land area and 7% of the world ocean.


	One major climate effect of sea ice is to seal off the underlying ocean from interaction with the atmosphere.
	Without an sea ice cover, high-latitude oceans transfers large amount of heat to the atmosphere, especially in winter.
	With an sea ice cover, the heat flux into the atmosphere is stopped. In addition, the ice surface absorbs little incoming solar radiation. Winter air temperature can cool 30°C or more near a sea-ice cover.


	Ice cores retrieve climate records extending back thousands of years in small mountain glaciers to as much as hundreds of thousands of years in continental sized ice sheets.
	The antarctic ice sheet has layers that extend back over 400,000 years.
	The Greenland ice sheet has layers that extended back 100,000 years.


	The Antarctic Ice Sheet holds the equivalent in seawater of 66 meters of global sea level.
	The Greenland Ice Sheet holds the equivalent of 6 meters of global seawater.


	This hypothesis argues that millennial oscillations were produced by the internal interactions among various components of the climate system.
	One most likely internal interaction is the one associated with the deep-water formation in the North Atlantic.
	Millennial oscillations can be produced from changes in northward flow of warm, salty surface water along the conveyor belt.
	Stronger conveyor flow releases heat that melts ice and lowers the salinity of the North Atlantic, eventually slowing or stopping the formation of deep water.
	Weaker flow then causes salinity to rise, completing the cycle.