Water, water everywhere? The Hydrosphere Water, water everywhere?

The Hydrosphere Definition: Earth’s outer layer of water, uniting water in all its state: liquid, gas, solid. Of this, 2.5% is freshwater Of this, 79% is frozen

Redividing the Hydrosphere We can “separate” the hydrosphere into 3 general categories: Inland water The cryosphere Ocean water

A) Inland Water

Inland water Definition How do we manage and study inland water? Fresh water bodies found on continents. This unites rivers, lakes and groundwater How do we manage and study inland water? We divide the continent up into catchment areas

Catchment areas Definition: A catchment area is the territory surrounding a waterway. All the water that falls in this territory will drain into the waterway

The red area shows the catchment area for the small river.

Catchment area Criteria to consider while deciding a watershed: Topography Geology (permeable rocks or not) Climate Vegetation Agriculture

B) The cryosphere

The cryosphere Definition: Consists of all frozen water on the Earth’s surface The cryosphere encompasses: Ice floes Glaciers Permafrost Frozen lakes and rivers Snow (etc.)

Ice Floes vs. Glaciers Ice floes are composed of ice floating on the oceans near the North and South poles. A glacier is a mass of ice on land formed by compressed snow What would be the effects if global warming melts these parts of the cryosphere?

Permafrost Permafrost is ground whose temperature has been 0C or lower for at least two years. This covers almost 50% of land in Canada.

C) The oceans

The Oceans Large masses of salt water The oceans are moved all over the world by currents. There are two types of currents Surface currents Subsurface currents (Deep currents)

1. Surface currents Surface currents Controlled mostly by wind Move horizontally, usually in the first 400 m Example: the golf stream

2. Subsurface currents (deep currents) Occur at a depth of more than 800 m Are caused due to the variation of density between water layers

Factors affecting subsurface circulation Density variation: Changes due to temperature The colder the water, the denser it is Changes due to salinity The higher the salinity, the denser the water is

Changes due to temperature Factors affecting the variation of temperatures: Depth The deeper the colder The mixed layer’s temperature relatively stable Seasons In winter, the water will loose its stored energy Latitude Increase in latitude, decrease in temperature At the equator the average surface temperature 25C-28C At the temperate zones the average temperature 12C-17C

Changes due to salinity variation Where does salt come from? Salt comes from the erosion of rocks and the dissolution of salts. As salt does not evaporate, rivers and groundwater also bring salt to the ocean. The higher the salinity, the denser the water will be.

3. Thermohaline circulation Huge “conveyor belt” effect connecting the surface and the subsurface circulations Responsible for the distribution of heat around the world