Sea ice Flashcards
(20 cards)
What are the 4 differences between Ice shelves and Sea ice
IS attached to land - SI freely floating
IS much thicker
IS Meteoric - SI Marine ice
IS driven by internal forces - SI driven by winds and ocean currents
What does sea ice do to the ocean
As sea ice cannot contain salt, it forms dense water which mixes and sinks (convection), removing buoyancy from the ocean and having a major influence on global ocean circulation.
What does salt do to cold water
It makes it denser
What causes the upwelling of warm water in the atlantic which brings heat to the N atlantic ?
The Southern Ocean winds
Ekman transport
When wind blows over the ocean, coriolis and vertical shear result in water transport 90° to the wind direction
What direction does water go with regards to the wind in the SH?
It goes 90° to the left, opposite for the NH
What is Ekman Pumping a result of?
The variation in wind speed across the open ocean result in differences in transport, this imbalance leads to pushing water down to the deep ocean or bring it up
What does the migration of the antarctic sea ice forming region to the north impact?
What term is attributed to this?
It results in a change location of buoyancy loss and gain, impacting location of upwelling and ocean current as a result. This could cool the NH
- This is the bipolar see saw
What process does the formation of latent polynya in sea ice continue?
This allows the continuation of the production of dense water
WHat’s up with the Maud Rise?
It brings warmer waters closer to the surface, creating sensitive polynya
What is thermobaricity?
Refers to water that will not sink at the surface but can sink when brought deeper
Why is SH sea ice expanding?
Principle theory in recent years is that a chnage in winds due to ozone depletion has cause this
ozone absorbs UV and heats the stratosphere
Ozone depletion = cooling = pressure change = strengthened winds
Low pressure centres in SH strengthen westerly winds as clockwise in SH
This brings more cold water north, promoting sea ice expansion
What is the Southern Annular Mode?
A climate pattern, influenced by the ozone, where there is a pressure difference between lattitudes -65° and -40°.
Leads to a general increasing trend in wind strength although it does vary a lot
Sigmond and Fyfe 2013 vs Fereira et al 2015
SandF found increased wind from southern annular mode led to decrease in sea ice extent.
This is correct as in the short term, strong winds upwell cold waters, long term, warm waters will be upwelled, as ekman driving will likely be warming the deeper ocean.
Ferreira et al clarified how it’s normal for there to be an advance before retreat
This retreat might be happening now
what is the temperature of CDW
2°C - 3°C
What determines the presence of warm waters on antarctic continental shelf?
- differing levels of sea ice formation (depth of mixing layer)
- differing wind forcing (proximity of westerlies to the coast)
- differing bathymetry (deep troughs)
What influences the depth of the mixing layer in the Ross and Weddell seas?
More sea ice growth, deeper mixing layer. Strong katabatic winds drive sea ice growth in RW seas
What is the influence of coriolis on water currents under ice shelves in the SH
In SH, coriolis pushes currents of the buoyant warm water flowing under the shelf, to the left - creating variability in melting
How does the change in thermocline depth influence interannual variability of melting?
The change in depth can allow the warm water to overcome submarine ridges which can block it.
Thermocline depth variability is in itself a result of variability in large scale winds
