BIOSCI 101 05-1 and 05-2

Why is WAIS more vulnerable to collapse than EAIS?

WAIS is mostly grounded on rock below sea level, making it vulnerable to warm seawater reaching the grounding line and melting ice.

How does snow become glacier ice?

Increasing pressure from overlying snow compresses it into dense glacier ice.

How does glacier ice move?

Gravity causes ice to flow down the surface slope.

Ice shelves - what happens at the grounding line?

Grounded ice becomes floating ice.

Why are ice shelves important?

They buttress the grounded ice sheet, helping stabilise it.

What are the two major ways ice shelves lose ice?

Melting underneath and iceberg calving.

At what temperature does Antarctic sea ice form?

About −1.9°C.

What happens to salt when seawater freezes?

Salt is expelled into the surrounding water as brine.

What is the sequence of sea-ice formation?

Frazil ice → grease ice → pancake ice → pack ice.

How can sensible heat produce a polynya?

Warm deep water rises and melts or prevents sea ice from forming.

How can latent heat produce a polynya?

Winds or currents move newly formed ice away from an area, leaving open water.

Why are polynyas important?

They can help produce Antarctic Bottom Water.

Why is Terra Nova Bay important?

It produces significant amounts of brine.

Why are Antarctic lakes generally biologically slow?

Ice limits light and mixing, slowing nutrient cycling and growth.

What makes Lake Vanda unusual?

It is very salty, stratified and nutrient-poor, with deeper water that is warmer, saltier, denser and low in oxygen.

What is special about the Onyx River?

It is Antarctica's longest exposed river.

Why don't subglacial lakes necessarily freeze?

Geothermal heat beneath thick ice can raise the temperature above the pressure melting point.