Great Bear Lake begins to freeze over as winter temperatures drop, creating a thick, icy surface across the lake.
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Great Bear Lake Freeze lake view
Lake Freeze Profile

When Does Great Bear Lake Freeze and Become Ice-Free?

A long seasonal ice cover with fast freeze-up, slow breakup and strong arm-to-arm differences

Freeze PatternUsually Fully FreezesFreeze-UpMid- to late November; 2002–2009 mean freeze onset was about November 14 and mean ice-on about November 29Ice-OffEarly to mid-July; 2002–2009 mean ice-off was about July 2, while 2000–2006 QuikSCAT water-clear timing averaged about July 10Full FreezeRegularLocationNorthwest Territories, Canada
Freeze Signature

Regular complete seasonal ice cover with a long winter ice season

Peer Reviewed Satellite MonitoringThe Cryosphere — AMSR-E Ice Phenology of Great Bear Lake and Great Slave LakeRemote Sensing of Environment — QuikSCAT Ice Phenology, 2000–2006Journal of Geophysical Research: Earth Surface — Seasonal Temperature and Circulation Patterns in Great Bear LakeEarth System Science Data — 41-Year Passive-Microwave Lake Ice Phenology RecordEvidence: High
Typical Ice DurationAbout 218 days in the 2002–2009 AMSR-E main-basin record
Ice Cover TypeComplete Seasonal Ice
Primary DriverHigh-Latitude Climate
Why It Freezes This Way

The long northern cold season produces complete winter ice, while great depth, heat storage, broad fetch and the five-arm basin geometry make spring breakup slower and spatially uneven.

Ice conditions are not a safety rating.Freeze dates and ice-cover records do not determine whether lake ice is safe for walking, skating, vehicles, or other activity.
Interactive Lake Map

Where Is Great Bear Lake?

Northwest Territories · Canada

65.8335° N · 120.7517° W
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Great Bear LakeNorthwest Territories · Canada
World View

Great Bear Lake on the Globe

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Great Bear Lake
Measurements

Measured Ice and Freeze Data

Mean Freeze-Onset, 2002–2009318day of year (~Nov 14)Peer Reviewed Satellite MonitoringThe Cryosphere — AMSR-E Ice Phenology of Great Bear Lake and Great Slave LakeEvidence: High
Mean Complete Ice-On, 2002–2009333day of year (~Nov 29)Peer Reviewed Satellite MonitoringThe Cryosphere — AMSR-E Ice Phenology of Great Bear Lake and Great Slave LakeEvidence: High
Mean Ice-Off, 2002–2009183day of year (~Jul 2)Peer Reviewed Satellite MonitoringThe Cryosphere — AMSR-E Ice Phenology of Great Bear Lake and Great Slave LakeEvidence: High
Mean Ice-Cover Duration, 2002–2009218daysPeer Reviewed Satellite MonitoringThe Cryosphere — AMSR-E Ice Phenology of Great Bear Lake and Great Slave LakeEvidence: High
Ice Year

Freeze and Ice Cover Through the Year

JANEstablished Seasonal Ice Cover
FEBEstablished Seasonal Ice Cover
MAREstablished Seasonal Ice Cover
APREstablished Seasonal Ice Cover
MAYMelt Onset
JUNBreakup
JULIce-Off to Open-Water Transition
AUGTypical Open-Water Period
SEPTypical Open-Water Period
OCTTypical Open-Water Period
NOVFreeze-Up
DECEstablished Seasonal Ice Cover

Month-level states are shown only when supported. Unclassified months remain explicitly marked.

Evidence

Evidence Behind the Freeze Profile

Recent satellite-era ice-off has shifted earlier

A pan-Arctic analysis for 2004–2019 reported a median water-clear-of-ice shift of about eight days earlier across Great Bear Lake, with spatial variation across the lake.

Peer Reviewed Satellite AnalysisThe Cryosphere — Recent Changes in Pan-Arctic Lake Ice TimingEvidence: Moderate
References

Sources

Great Bear Lake normally develops complete seasonal ice cover. The transition is not instantaneous: satellite records place freeze onset across the lake in mid-November, with near-complete ice-on near the end of November, while spring melt begins in May and can continue into July before the whole lake is clear.

Why Freeze-Up Is Shorter Than Breakup

Autumn cooling acts quickly once surface waters approach the freezing point. The 2002–2009 AMSR-E record puts roughly two weeks between freeze onset and ice-on across Great Bear Lake. Spring is slower. Melt can begin while most of the surface remains ice-covered, and the published satellite record shows roughly six to seven weeks between melt onset and final ice-off.

That long spring transition is visible in field observations as well. During the 2008–2009 season, freeze-up was complete by November 24, 2008, and the lake became ice-free between July 12 and 15, 2009, for about 230 days of ice cover. A single season should not be treated as the long-term average, but it shows how long ice can persist after spring warming begins.

The Five Arms Do Not Freeze and Clear Together

Great Bear Lake’s five-arm basin does not change state everywhere at once. QuikSCAT mapping for 2000–2006 found freeze onset appearing first in the northern arm and along shorelines. Melt onset appeared first in the eastern arm, while water cleared first in southeastern and western arms. AMSR-E mapping also found that ice could remain longer in Smith Arm and Dease Arm during some seasons.

This spatial pattern matters when reading a lake-wide freeze or breakup date. A date calculated from satellite pixels summarizes a moving boundary across a very large surface; it does not mean every bay, arm and central-water sector changed on the same day.

Why Such a Deep Lake Still Freezes Over

Great Bear Lake covers about 31,153 square kilometres, has a mean depth near 71 metres and reaches about 446 metres at its deepest point. That volume stores heat through the open-water season, so autumn cooling must remove a large amount of stored energy before stable ice can spread across the lake.

Its latitude supplies a long cold season strong enough to overcome that heat storage. Basin shape then modifies the sequence: shallow margins can cool quickly, deep water retains heat longer, and wind and mixing move heat through the water column. The result is regular complete winter ice, but with local timing differences around the five arms and a drawn-out spring breakup.

What Ice-On and Ice-Off Mean on Great Bear Lake

Different monitoring systems do not define every ice event in exactly the same way. The AMSR-E study separates freeze onset from ice-on, and melt onset from ice-off. The later 1979–2019 passive-microwave record used lake-pixel thresholds to distinguish the start and end of freeze-up and breakup while excluding nearshore pixels that were more vulnerable to land contamination.

QuikSCAT, AMSR-E and direct observations can therefore produce dates that differ by days or, in some cases, longer. Those differences do not automatically indicate a conflict. For Great Bear Lake, a seasonal window and the direction of spatial progression are more informative than treating one calendar date as fixed for every year and every part of the lake.

Earlier Ice Clearance in the Recent Satellite Period

A pan-Arctic satellite analysis for 2004–2019 reported a median water-clear-of-ice shift of about eight days earlier across Great Bear Lake. The pattern varied spatially across the lake.

That observation points to earlier summer ice clearance during that study period, not the disappearance of Great Bear Lake’s normal winter ice cover. Year-to-year variability remains large, so the 2004–2019 result is best read as a dated satellite-era change rather than a permanent replacement for the lake’s seasonal calendar.

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