Sea Ice Climatic Atlas Terminology
Many of the terms used in describing sea ice apply with equal validity to lake ice and/or river ice. A complete manual of ice terminology, classification, standard ice reporting codes and ice reconnaissance practices and procedures used in Canada are available from the Canadian Ice Service, Meteorological Service of Canada of Environment Canada under the title MANICE.
Ice climatology uses specific terminology to describe specific ice-related concepts. Here is a short list
of some useful recurring terms you are likely to find in our ice cllimate products and documentation.
- Breakup
- This term refers to a particular length of time in which ice disappears in a given area (generally 1 to
2 weeks).
However, breakup does not necessarily imply a decay or melt of ice, but can also indicate a
movement of ice out of a particular area.
- Freezeup
- This term refers to a particular length of time in which ice appears in a given area (generally
1 to 2 weeks).
However, freezeup does not necessarily imply a growth of ice, but can also indicate
a movement of ice into a particular area.
- Frequency
- Akin to the term "probability"', as used in the field of statistics, meaning:
"...the chance or likelihood that a particular event will occur. If each possible outcome is equally
likely, this chance of occurrence of the event may be defined as follows: probability of occurrence =
X/T where X [is] the number of outcomes for which the event we are looking for occurs [and] T [is] the
total number of possible outcomes..."
(Reference: Applied Statistics: A First Course, M. L. Berenson, D. M. Levine, D. Rindskopf, 1988 Prentice-Hall Inc., p. 133).
- Ice concentration
- "...the ratio expressed in tenths
describing the area of the water surface covered by ice as a fraction of the whole area."
(Reference: MANICE* (Manual of Standard Procedures for Observing and Reporting Ice Conditions, AES,
Environment Canada, pp. 1-6).
- Median
- Here are two accurate definitions for this term:
"The median is the middle value in an ordered sequence of data. If there are no tied (equal) values, half of the observations will be smaller and half will be larger than the median. The median is unaffected by any extreme observations in a set of data"
(Reference: Applied Statistics: A First Course, M. L. Berenson, D. M. Levine, D. Rindskopf, 1988
Prentice-Hall Inc., p. 40).
"The median is employed with ice statistics due to the ordinal nature of the ice attributes. For example, 9+/10 ice concentration is greater than 9/10 concentration and first-year ice is greater (thicker) than grey-white ice."
(Reference: Sea Ice Climatic Atlas*, East Coast of Canada, 1971-2000. 2001, Kaice-Tec Reproduction Ltd., p. 7).
- Normal
- A climate product summarising a particular attribute (e.g. ice concentration or predominant ice type).
Thirty years is the standard length of time for constructing a statistical summation of a time period
for use in comparing to a standard, or normal.
- Predominant ice type
- Ice type in the greatest concentration within a given area.
- Region
- These are the operational regions designated by the CIS.
The regions for climate products vary
because of changes in the extent of the ice analyses throughout the years. The most apparent
difference is the West Arctic.
- Time period
- These are the source years used to compile the various climate products.
