2.5 Ice Thickness Observations

Ice thicknesses are measured routinely at selected shore stations, ranging from the Arctic to the Great Lakes. Occasional thickness measurements are obtained from icebreakers. All thickness observations are desirable and should be obtained where and when possible

These measurements serve to help verify aerial and shipboard observations by providing the exact WMO thickness category at the point of measurement. This data can be used to compare estimates made in the same area at the same time or during future observations. It can also be used to predict future ice thicknesses.

Chapter 7 describes the procedures for coding and reporting ice-thickness observations.

Figure 2.2: Diagram of Ice Concentrations from an Aerial Perspective

	0/10	Ice Free
	less than 1/10	Open Water
	1/10		2/10		3/10	Very open drift
	4/10		5/10		6/10	Open drift
	7/10		8/10	Close pack/Drift
	9/10	Very close pack
	9+/10	Very close pack
	10/10	Compact/Consolidated ice

Figure 2.3: Iceberg Size

Iceberg Size	Height above sea surface (meters)	Length (meters)	Weight (Megatons)
Growler	less than 1 m	less than 5 m	0.001
Bergy Bit	1 m to less than 5 m	5 m to less than 15 m	> 0.01
Small Berg	5 m to 15 m	15 m to 60 m	>0.1
Medium Berg	16 m to 45 m	61 m to 120 m	2.0
Large Berg	46 m to 75 m	121 m to 200 m	10.0
Very Large Berg	Greater than 75 m	Greater than 200 m	Greater than 10.0

Figure 2.4: Iceberg Shape

Shape	Average height to draft ratio
Tabular	1:5
Non-Tabular	1:5
Domed	1:4
Pinnacle	1:2
Wedge	1:5
Drydock	1:1
Blocky	1:5