to Sea-Ice Nomenclature Overview page
This is a clickable image. Point your mouse at a topic you would like to further explore and it will take you to a short description of the ice type of concern. Also see the interpretation below the chart.
This chart describes the sea ice formation and growth process. Time increases from left to right; and first order categories are expanded vertically. In all cases ice formation begins with frazil ice production, but depending on surface water conditions, the nature of ice growth varies. Under calm conditions, nilas ice growth is favored (little convective mixing of frazil crystals), while under, windy, rough conditions frazil ice production is enhanced (lots of convective mixing) leading to slush, grease ice, and pancake ice as surface roughness increases. New ice grows through a transition layer, then becoming young ice. Categories of more mature ice (thicker than 30 cm.) are not discussed in detail.
It is interesting to ponder how long each ice type
can exist in nature, based on the thickness classifications as
described by the WMO nomenclature system.
The surface energy balance can be used to investigate
growth rates of ice of varying thicknesses. Values for terms in
the surface energy balance were taken from Maykut (1978) "Energy
Exchange Over Young Sea Ice in the Central Arctic" . To come up with
a range in growth rates, I calculated growth rates for both September
and January, with hopes of capturing growth rates in early season
when young ice first appears as well as growth rates during the
depths of winter when they are at their maximum values. A
growth rate expression was taken from Carol Pease's 1987 paper "The
Size of Wind-Driven Coastal Polynyas".
where
dH/dT=ice growth rate
(1-a)Qr= incoming shortwave radiation considering albedo
Qld=downward longwave radiation
Qlu=upward longwave radiation
Qs=sensible heat flux
Qe=latent heat of evaporation
rhoice=density of ice=0.95 X103 kg m-3
L=latent heat of fusion for saltwater=3.34 X 105 j kg-1
The results of the exercise are tabled below,
giving a back of the envelope idea of how long one can expect various
ice types to exist under conditions common to the arctic in both
September and January.
|
Ice |
Class |
dH/dt |
Existence time |
Existence time |
|
open water |
frazil |
0.01-0.23 m/d |
~few days |
hours to days |
|
0.05 m |
dark nilas |
0.01-0.12 m/d |
<5 days |
<12 hours |
|
0.10 m |
light nilas |
0.0075-0.175 m/d |
<6.6 days |
<7 hours |
|
0.20 m |
grey-white |
0.005- 0.05 m/d |
<40 days |
<4 days |
|
0.40 m |
Thin first year |
0.003-0.03 m/d |
~130 days |
~13 days |
|
0.80 m |
Med. first year |
0.001-0.02 m/d |
~500 days |
~25 days |
|
3.0 m |
multi-year |
0.003-0.004 m/d |
indefinite |
indefinite |