ࡱ> =?<q #bjbjt+t+ -6AA]8888888LLLLL X,L8 8   $  `# 8# 88*88LL888888 LLSEASONAL OUTLOOK SEA ICE CONDITIONS FOR: BAFFIN BAY, DAVIS STRAIT, LABRADOR SEA AND THE SOUTHWEST GREENLAND WATERS SUMMER 2001 NATIONAL / NAVAL ICE CENTER Historically the 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 typically break sometime between the last half of July and the third week of August. The remaining ice will be composed of rotten floes that are rapidly deteriorating, and disappear completely by mid-September. The two main objectives of the Eastern Seasonal Outlook are to forecast the thinning of the ice bridge for planning escorted shipping operations, and the breaking of the ice bridge for planning for unescorted operations. Overall, conditions throughout the route across the Labrador Sea, Davis Strait and Baffin Bay are expected to be on schedule to slightly ahead of schedule for the 2001 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 18 July 20 August 3 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. Page 1 Freezing Degree Day (FDD) Accumulations and Ice Thickness (Table 2) are shown for the 2000-2001 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 slightly thinner than the mean climatological thickness in all cases for mid-May 2001. The Freezing Degree Day values for the stations along the western shore of Greenland (Thule, Upernavik) were both below normal for mid-May 2001. The two stations reporting on the western shore of Baffin Bay and Davis Straits (Cape Dyer, Frobisher Bay) are also running below the normal FDD values and theoretical thickness. Table 2 Current and Climatological Freezing Degree Days / Theoretical Thickness (Freezing Degree Days - Degrees C) (Theoretical Thickness - Centimeters) LOCATION MAXIMUM MINIMUM MEAN 15 MAY 01 FDD / THK FDD / THK FDD / THK FDD / THK Thule 5093 / 178 3721 / 142 4496 / 168 4257 / 161 Upernavik 3654 / 149 2207 / 75 3043 / 134 2795 / 127 Sondrestrom 4010 / 146 1915 / 26 2927 / 108 0 / 0* (2769 / 105)^ Cape Dyer 4607 / 171 3204 / 137 3927 / 155 3692 / 149 Frobisher Bay 4660 / 171 3182 / 122 3866 / 155 3452 / 143 Angmagssalik 1793 / 94 949 / 41 1260 / 81 0 / 0* Resolution Is. 3766 / 152 2066 / 105 2927 / 132 0 / 0* * Values reset before 15 May 2001. ^ Values at Sondrestrom on 01 May 2001, before they reset. Page 2 Table 3 lists the distance in nautical miles from select ports to the nearest ice edge on the 4th of May 2001, verses the mean distance for the 1st of May. As can be seen from Table 3, the position of the ice edge is greater than the mean at all locations with the exception of Angmagssalik on the eastside of Greenland. Table 3 Distance From Selected ports to the ice edge in nautical miles. PORT MEAN (May 1) PRESENT (May 4, 2001) Thule 540 605 Upernavik 210 265 Cape Dyer 130 140 Frobisher Bay 240 285 Angmagssalik 60 40 Resolution Is. 80 160 Figure 2 indicates the climatological maximum, mean and minimum positions of the ice edge for May 15th. Figure 3(a-e) depicts the actual ice conditions present for the week of 21-25 May, 2001. The ice extent in the St. Lawrence, Grand Banks, and Labrador Sea lies near a climatological mean. The ice extent in the Davis Strait and Baffin Bay were also near a climatological mean. By the week of 21-25 May, the waters in the vicinity of Disko Island had become open water. Page 3 Several factors were considered during the preparation of the outlook. Their description and weight in the outlook are discussed in the following paragraphs. Values plotted on standard ice thickness curves for Thule and Upernavik showed values much thinner than the mean climatological ice thickness curves for the early winter season, but trending closer to the mean by the beginning of May. Freezing Degree Days (FDD) data for Thule, Upernavik, Cape Dyer and Frobisher Bay showed that all 4 stations were below normal FDDs for the winter of 2000-01, leading to thinner than normal ice thickness. Values for freezing degree days accumulation and ice thickness are compared with past years and shown in Table 2. As noted in Table 3 the distances to the ice edge are above the mean for all stations, with the exception of Angmagssalik on the eastern Greenland coast. Greater ice extents seem to be in contradiction to the lower than mean ice thickness and FDD totals exhibited in the reporting stations. However, it is important to note that extensive belting and stripping of the ice was occurring at the time that the distance to the ice edge was measured (May 4), and this could have contributed to the larger than normal distances seen. owever Next, we compared the ice edge and inner pack concentrations from the week of May 21-25 to our climatological database of archived charts to find an analog year. After comparing the ice edge and re-occurring polynyas from May of this year to May of years past, 1987, 1976 and 1988 were chosen as the best analogs for the current ice conditions. Unescorted transit times for these three analog years were the 05 August, 03 August, and 20 July, respectively. These dates are all earlier than normal to near normal for the appearance of unescorted transit conditions. With the agreement of the FDD, theoretical thickness and the analog years indicating a slightly earlier than normal opening, we feel fairly confident in our initial forecast. Another guidance is the 30day 700mb forecasts of heights and height anomalies from NCEP. According to the forecast charts, there should be a trough of low pressure over Baffin Bay. This sort of pattern would indicate northwesterly or northerly wind flow over Baffin Bay. Whereas temperatures may be relatively cooler, the northerly wind direction combined with a strong southward moving current along the western Baffin Bay should help clear the northern area of Baffin Bay of ice earlier than normal. In the third week of May, we met with ice forecasters from the Canadian Ice Service (CIS) to compare our findings. The East Seasonal Outlook produced by CIS is of a larger scope, and their forecast ports are different from the NIC Outlook, but the general information that goes into their forecast is similar to what is used at NIC. The CIS Seasonal Outlooks can be accessed on the CIS homepage at  HYPERLINK http://www.cis.ec.gc.ca http://www.cis.ec.gc.ca. Figure 4 shows mean climatological conditions for July 15. Figure 5 shows ice conditions on July 15 of our chosen analog years (1987, 1976, and 1988). Due to the combination of factors listed above, the unescorted opening of the ice route for the transit to Thule, Greenland is forecasted to be near to slightly earlier than normal for the summer of 2001. Page 4  N U z46fh5<KRQ[!!!!! 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