**SEASONAL OUTLOOK**

**SEA ICE CONDITIONS FOR:**

**BAFFIN BAY, DAVIS STRAIT, LABRADOR SEA**

**AND THE SOUTHWEST GREENLAND WATERS**

**SUMMER 1999**

**NATIONAL ICE CENTER / NAVAL ICE CENTER**

Historically Baffin Bay melt does not begin until June, although the
first signs of the North Open Water are observed in May. During the
beginning of the melt, the western boundary of the pack ice begins to
recede eastward, meeting the north open water. A broad flaw lead forms
along the Greenland coast and gradually moves northward to Melville Bay.
The pack ice begins receding, leaving an ice bridge across Baffin Bay
(from NW Greenland to Central Baffin Island). This ice bridge will break
sometime between the last weeks of July and the third week of August.
The remaining ice will be composed of rotten floes that are rapidly
falling apart, which by mid-September will disappear completely. The
main objective of the Eastern Seasonal Outlook is to forecast the
thinning of the ice bridge to help plan escorted shipping operations,
and to forecast the breaking of this ice bridge to help plan for
unescorted operations.

Overall, conditions throughout the route across the Labrador Sea, Davis
Strait and Baffin Bay are expected to be slightly ahead of schedule for
the beginning of the upcoming shipping season. **Table 1** provides the
forecast opening dates for the transit to Thule, Greenland.

**Table 1**

**Forecast and Normal Opening Dates**

**Thule, Greenland**

**PORT FORECAST NORMAL FORECAST NORMAL**

**ESCORTED ESCORTED UNESCORTED UNESCORTED**

**OPENING OPENING OPENING OPENING**

**DATE DATE DATE DATE**

Thule July 15 July 20 July 31 August 5

Escorted: Concentrations of ice encountered on the transit to Thule will
be 7/10s or less and any fast ice will be in a weakened state.

Unescorted: Concentrations of ice encountered on the transit to Thule
will be 1/10 or less.

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Freezing Degree Day (FDD) Accumulations and Ice Thickness (**Table 2**)
are shown for the 1998-1999 winter season and historical Maximum,
Minimum, and Mean data for selected locations in the Baffin Bay / Davis
Strait / Labrador Sea area. (See **Figure 1** for port locations).

Ice thickness values are thinner than the mean climatological thickness
in all cases for early May 1999. The Freezing Degree-day values for all
stations are also below normal for the start of May 1999. Both give an
indication of a slightly early then normal navigation season.

**Table 2**

**Current and Climatological Freezing**

**Degree Days / Theoretical Thickness**

**(Freezing Degree Days - Degrees C)**

**(Theoretical Thickness - Centimeters)**

**LOCATION MAXIMUM MINIMUM MEAN 09 MAY 99**

**FDD / THK FDD / THK FDD / THK FDD / THK**

Thule 5093 / 178 3721 / 142 4496 / 168 4369 / 164

Upernavik 3654 / 149 2207 / 75 3043 / 134 2536 / 120

Sondrestrom 4010 / 146 1915 / 26 2927 / 108 2737 / 125\*\*

Cape Dyer 4607 / 171 3204 / 137 3927 / 155 3534 / 145

Frobisher Bay 4660 / 171 3182 / 122 3866 / 155 3476 / 144

Angmagssalik 1793 / 94 949 / 41 1260 / 81 959 / 54\*

Resolution Is. 3766 / 152 2066 / 105 2927 / 132 0 / 0\*

\* Values reset before 09 May 99.

\*\* Value is suspect.

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**Table 3** lists the distance in nautical miles from select ports to
the nearest ice edge for the climatological mean and the present
distance. As can be seen from Table 3, the position of the ice edge is
less than the mean at Thule and Upernavik, at the mean at Cape Dyer, and
greater than the mean distance at the southern stations.

**Table 3**

**Distance From Selected ports to**

**the ice edge in nautical miles.**

**PORT MEAN(May 1) PRESENT (May 3, 1999)**

Thule 540 490

Upernavik 210 190

Cape Dyer 130 130

Frobisher Bay 240 290

Angmagssalik 60 70

Resolution Is. 80 140

**Figure 2** indicates the climatological maximum, mean and minimum
positions of the ice edge for May 15th. **Figure 3** depicts the actual
ice conditions present on the May 17, 1999. The ice extent in the
northern Labrador Sea lies between a climatological mean and a maximum.
The southern Labrador Sea and Baffin Bay from Disko Island to 60N/60W is
near a climatological mean. The openings of the North Open Water and the
polynyas in the vicinity of Disko Island were near the mean and indicate
that the northern section of Baffin Bay is also at a climatological
mean. Two charts of note are the Foxe Basin and Hudson Bay, both regions
are running at the minimum. Some areas of the Foxe Basin and Hudson Bay
may be at record melt out conditions.

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Several factors were considered during the preparation of the outlook.
Their description and weight in the outlook are discussed in the
following paragraph.

Values plotted on standard ice thickness curves for Thule, Upernavik and
Angmagssalik showed values below the mean climatological curves for the
entire winter season. Temperatures from the late winter 1999 and early
spring 1999 showed warm temperatures south of Davis Strait with normal
or cool values in Baffin Bay. When values for freezing degree-days
accumulation and ice thicknesses are compared with past years as shown
in **Table 2** all stations were below the climatological mean. As noted
in **Table 3** the distances to the ice edge are below the mean in the
North and above the mean in the South. The greater distance to the edge
in the southern Baffin Bay and Davis Straits would normally lead the
forecaster to believe a heavier winter ice season was experienced. After
further investigation, the heavier ice conditions were determined to be
a result of the extreme melt out in the Foxe Basin. The early break out
of the Foxe Basin created a greater volume of ice in the Labrador Sea
and southern Davis Straits than would be anticipated in a milder ice
year.

Next, we compared the ice edge and concentration conditions from the
Gulf of St. Lawrence to North Open Water, and we determined 1986 as the
best fit for an analog year. When we looked at the Escorted and
Unescorted transit times in 1986, they were between slightly late and
normal. This caused some concern since the analog year transit time
didn't match what our other indicators were telling us. This temporarily
lowered our confidence in the dates chosen for the seasonal forecast. We
next consulted the Canadian Ice Service (CIS) which produces a similar
product for their summer shipping season. In examining the Canadian's
temperature and thickness data, we saw a similar trend to our earlier
findings in that the thicknesses and FDD accumulations were less than
the mean. Forecasters from CIS were in agreement with our initial
forecast for a slightly earlier than normal transit season. Therefore we
decided to throw out 1986 as the analog year. Whereas 1986 matched our
current ice conditions, the trend for a much colder summer, which was
the case in 1986, is not the likely scenario for the summer of 1999.
**Figures 4 and 5** show mean climatological and expected ice conditions
for July 15, 1999.

Due to the combination of factors listed above, the opening of the ice
route for the transit to Thule, Greenland is forecasted to be
approximately one week earlier than normal.

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