Environmental Science - 2.1.2 - Changes in Oceans and Cryosphere
what is the north atlantic conveyor belt
also the gulf stream, involves the movement of layers of surface and deep water that distribute heat and control the climate
what processes drive the gulf stream
friction with prevailing winds on the ocean surface to the north east causes surface water to flow north east
water in north east atlantic sinks as it cools at the poles, drawing in warm water to replace it
what changes to the gulf stream can be seen due to climate change?
higher atmospheric temperatures cause land ice in greenland to melt and flow into the sea, diluting the saline seawater to freshwater and causing it to sink beneath seawater, disrupting and slowing the rate
what is el nino
the sequence of naturally occuring events every 2-7 years and sees change in wind patterns which result in different precipitation patterns and current directions
how do wind patterns change due to el nino
trade winds travelling west from south america to indonesia change direction, travelling from indonesia to s. america
what is the normal pattern in a regular year (not el nino)
nutrient rich water from the deep ocean is drawn up along the coast of south america, causing large algal blooms that provide a food source for fisheries
what is the pattern in an el nino year?
wind direction changes, moves from indonesia to s. america, causes surface currents to change direction too
how does el nino affect food webs
no upwelling to replace water drawn away by currents, no algal blooms due to nutrient deep water, so no food source for fish. fish die out and predators have no food, prey populations increase
how does el nino cause drought
there is no warm air carrying moisture rich air inland towards Australia and Asia
how does el nino cause heavy rain and floods in s. america?
swapping of wind direction causes warm water to move eastward, which retain water vapour for longer and evaporation is increased
what global impacts does el nino cause
droughts in north east and south africa, and china
fewer hurricanes in north atlantic
fewer cyclones in japan
how is sea level rise caused by thermal expansion?
warmer atmosphere heats seawater which expands by 30%, causing the volume of the sea to increase and sea levels rise.
how does melting land ice cause sea level rise
warming atmosphere causes ice to melt. land ice increases the volume as it is not already in the sea
does melting floating ice cause sea level rise?
no, it contracts when melting and occupies the same volume as ice below sea level
how is the amount and duration of snow and ice affected by CC
higher temperatures means the duration of ice and snow on the ground is shortened. snow and ice also melts quicker when its warmer
how is extent of glaciers affected by CC
glaciers moving towards the sea due to effect of gravity may have the snout of the glacier melt faster than it is moving forward, causing the extent of the glacier to be reduced
how is the speed of glacier movement affected by CC
meltwater from the top of a glacier may move to the bottom through cracks where it can lubricate the ice over the rock and allow it to move quicker. increasing temp means more meltwater and lubrication so quicker glacier
what is a land ice cap
ice covering less than 50,000 km2 of land, thick enough to have its own topography
what is an ice sheet
ice covering an area of over 50,000km2, these Greenland and Antarctica
how is the area of ice changing
decreasing due to higher temperatures, less ice means less albedo and less sun reflected, more ice melted, positive loop
how is the thickness of ice changing
during winters at the poles, ice sheets expand because of the low temps, with a warming climate this does not occur to the same extent, and is also relatively thin as it is ice that has crystallised in the sea
how do ice sheets break up
grounded ice sheets may float and break up earlier as sea levels rise as the ice breaks off earlier.
what is an ice shelf
a large platform of glacial ice floating on the ocean