2:Sea Ice Flashcards
What is ice draft? What is the freeboard?
The fraction of floating ice below the ocean surface. The fraction above the ocean surface is the freeboard.
How has the ice thickness been measured in the past and in the presence?
The past: submarines with upward-looking sonars measuring the ice draft.
The presence: satellite measuring the freeboard.
What is drift ice?
pack ice?
Drift ice: any area of sea ice (ice formed by freezing of water) that is not landfast/not connected to land or any other fixed object. –> therefore mobile ice that is carried along with wind and sea currents.
Pack ice: When drift ice is driven together into a large single mass (>70% coverage), it is called pack ice.
Mention (5 points) how sea ice impacts the ocean below and the climatology.
The cover of sea ice suppresses wind stress and wind mixing, reflects a large portion of incoming solar radiation, imposes an upper limit on the surface temperature, and impedes evaporation, impacts the heat transfer.
How does the wind and water stress impact the ice pack?
How high can pack ice be?
Wind and water stresses keep the ice pack in almost continuous motion, causing the formation of cracks (leads), open ponds (polynya) and pressure ridges.
Along these ridges pack ice may be locally stacked high and project downward 10-25 m into the ocean
Where do you have seasonal periods of sea ice, and where is the sea ice more permanent?
Although “perminent” sea ice, how much area is open water in these areas and why?
seasonal: 60-75N
“perminent”: above 75N
–> approx 10% is open water due to the continious forming of polynyas and leads.
When seawater freezes, the salt is expelled as brine. Approx how saline is
- New sea ice
- 1-year-old sea ice
New sea ice: approx 0.4 - 0.6 % salinity
1 year-old: approx 0%
What is multiyear sea ice? How does it look? How thick is it? How is the characteristics of multiyear ice compared to younger ice?
What is young/new sea ice? How does it look? How thick is it?
multiyear: Sea ice older than 1 year.
Can be distinguished by its rounder, smoother surface, and pale blue colour.
The measures ice draft for (multiyear) ice Is approx 1,8m thick. (used to be 3,1m)
Is stronger icea s the hardness and strenght of icee increase as the salt is expelled.
young: 1 year old or less.
Looks more jagged and more gray in colour.
approx 2 m thick.
What is fast ice?
Fast ice (also called land-fast ice, landfast ice, and shore-fast ice) is sea ice that is “fastened” to the coastline, to the sea floor along shoals or to grounded icebergs.. Fast ice is not moved by wind or currents.
