Into the Abyss Flashcards
How is the ocean stratified?
by density (warm and fresh= less dense than saline and cold)
what is the thermocline
thin layer in body of water where there is a rapid drop in temperature with depth
what is the pycnocline
thin layer where there is a rapid increase of density with depth
what is the dominant control on density
temperature
other than temperature, how can water change in density
exchanging of material to another body of water
explain the origins of salinity
streams carry dissolved substances to the sea-> made of cations from exposed crustal rock and anions likely from the mantle
how can the concentration of dissolved materials change?
addition or removal of freshwater due to rates of precipitation and evaporation
what is the halocline
a thin layer of water where there is a rapid change of salinity with depth
how can one track how two water masses mix with each other?
see how their characteristics change
give three depth layers in the ocean
surface zone/mixed layer, thermocline/halocline/pycnocline, deep zone
what percentage of the ocean’s volume is in the deep zone?
80%
at what latitudes is the deep zone in contact with the atmosphere?
high latitudes
to what depth is plant and animal life restricted?
200m (photic zone)
what is calcareous ooze and where can it be found
layers of muddy, calcium carbonate bearing soft rock sediment on the seafloor, low to mid latitudes
what organisms are favoured by warm surface water and why
carbonate secreting organisms, not found in deeper water due to acidity
name the largest body of polar surface water
antarctic circumpolar water, extends to the ocean floor
roughly what depths are upper water masses at?
550-1500m
where and how are deep and bottom water masses formed?
cold polar seas, cold winds cool water and cause it to sink
how is north atlantic deepwater formed?
intense surface cooling and convective overturning-> becomes trapped in basins, overflows ridges and disperses
how is antarctic bottom water formed?
cold winds and sea ice cool cool surface water as cold as possible without freezing, mixes with dense brine and sinks to deep ocean
what is a gyre?
large subcircular ocean system made up of major ocean currents
why is the centre higher than the periphery in the NA ocean gyre>
converging currents force it upwards
explain the motion of currents in a gyre
coriolis effect and the pressure gradient balance and create a system in dynamic equilibrium so that water flows across rather than down the slope-> geostrophic currents
what are warm and cold core rings?
meanders in currents like the gulf stream
by what measure is the speed of thermohaline circulation measured
metres per day
where do deep waters enter and leave the surface current system?
southern ocean
why would the breakdown of thermohaline circulation alter climate?
thermohaline circulation is an important transporter of heat
what determines the solubility of gas?
partial pressure: more soluble when water is cold, fresh and under high pressure
how are the oceans ventilated
oxygen rich water sinking
what gas is very soluble
CO2
