**SEASONAL OUTLOOK**

**SEA ICE CONDITIONS FOR THE ALASKAN NORTH COAST**

**SUMMER 2003**

**NATIONAL / NAVAL ICE CENTER**

Ice conditions are expected to be lighter than normal during the 2003
navigation season. Table 1 presents the relative severity of ice
conditions each season between 1953 and 2002. The National/Naval Ice
Center (NIC) forecasts the 2003 season to rank between 12 and 15 in the
index of our 50 years of record. In years that rank in this portion of
the index, the sea route between Wainwright and Prudhoe Bay is generally
open (less than 5/10's ice concentrations) from the end of July through
early to mid-October, during which a significant period of ice free
navigation is possible. It is important to note, however, that during a
typical ice navigation season the ice edge does not recede a significant
distance northward from the Alaskan coast. With the lack of a large
coastal lead, there is the potential for encroachment of higher
concentrations of sea ice into the shipping lanes at any time throughout
the summer season. Table 2 can be used to compare the 2003 forecast to
the past 50 years (1953-2002) of climatological medians and extremes.

Output from the NIC long-range prediction model (Barnett, 1980) contains
pre-season indicators that the summer of 2003 will be lighter than
normal conditions, this is also supported by a new method of calculating
the severity index developed by Sheldon Drobot of the University of
Colorado and several other factors: (a) Warmer than normal temperatures
across much of Alaska during the 2002-2003 winter including a well above
normal October, the normal start of the freeze up, and a well above
normal April. (b) Statistical method of computing the outlook using
surface pressures, heights and temperatures at specific sites point to a
lighter than normal year. (c) The multi-year ice line is further north
than normal due to the record melt-out of the ice in the eastern Chukchi
and western Beaufort seas during the summer of 2002. (d) Theoretical ice
thickness for Point Barrow has been close to climatological minimums all
winter. (e) Ice conditions in the Bering, Chukchi and Beaufort Sea
during May of 2003 that are similar to conditions seen in May of 1989
and 1979, which were also light years.

Eastward, from the vicinity of Herschel Island to the Canadian
Archipelago, a normal season is expected during 2003 summer season.
Trouble-free operations should develop in the coastal waterway from
Herschel Island to the Amundsen Gulf by mid-July and continue into
middle to late October. A seasonal outlook for this area is also
prepared and issued by the Canadian Ice Service
[http://ice-glaces.ec.gc.ca](http://ice-glaces.ec.gc.ca/).

> **TABLE 1**

**SELECTED SEA ICE DATA AND SEVERITY INDEX FOR**

**THE NORTH COAST OF ALASKA 1953-2002**

**SEVERITY 1 2 3 4 5 6 7 8**

RANK YEAR nmi nmi nmi nmi date date #days #days

MILDEST\-\-\-\-\-\-\-\--1 1958 50 150 50 210 07/19 10/25 92 99+

> 2 1968 25 165 30 200 07/19 10/18 86 91

3 1998 15 105 20 240 07/15 10/21 72 100

4 1993 0 130 5 185 07/18 11/07 64 112

> 5 2002 0 135 18 225 08/13 10/14 32 64
>
> 6 1962 25 150 30 150 07/19 09/30 49+ 68+

7 1973 5 80 5 190 07/31 10/20 73 82

8 1954 20 115 20 210 08/01 09/30 38+ 61+

9 1997 28 150 40 150 08/08 10/10 47 63

10 1963 5 130 5 130 08/13 10/18 67 67

> 11 1990 0 90 40 90 07/23 10/12 75 105
>
> 12 1961 15 105 15 135 07/25 09/24 49+ 62+
>
> 13 1996 10 65 70 155 07/16 09/25 37 71
>
> 14 1979 0 125 0 125 08/04 10/08 31 56
>
> 15 1989 10 70 55 110 07/19 10/22 34 95
>
> 16 1974 10 100 10 100 08/06 10/05 35 61
>
> 17 1978 5 70 30 95 07/25 10/09 35 76
>
> 18 1986 10 80 10 110 07/29 10/21 30 58
>
> 19 1999 15 45 45 105 07/30 10/08 56 70
>
> 20 1977 5 55 25 85 08/02 10/15 63 74
>
> 21 1959 20 65 20 65 07/19 10/06 42 86
>
> 22 1995 30 30 50 50 07/15 10/17 70 94
>
> 23 1972 0 60 30 90 07/31 10/01 45 63
>
> 24 1982 0 85 0 95 08/03 10/10 21 69
>
> 25 1994 10 35 10 60 08/05 09/24 44 55
>
> 26 1957 5 45 70 60 08/01 10/06 18 67
>
> 27 1987 0 10 0 85 08/05 10/30 35 59
>
> 28 1981 0 0 35 100 07/26 10/01 0 66+
>
> 29 2000 10 70 10 75 07/31 10/02 19 33
>
> 30 1985 0 35 0 55 08/01 10/15 22 52
>
> 31 1967 15 0 30 50 07/25 10/12 UNK 68
>
> 32 1984 0 25 0 50 08/11 10/15 21 42
>
> 33 1966 5 0 5 45 08/01 10/22 24 65
>
> 34 1992 15 0 15 75 08/09 09/19 24 37
>
> 35 1965 0 10 0 70+ 08/25 09/25 25 32
>
> 36 2001 0 25 15 25 08/17 10/08 26 52
>
> 37 1980 15 25 15 25 08/05 09/30 11 42
>
> 38 1953 0 0 5 35 07/27 09/16 5 52+
>
> 39 1976 0 15 0 15 08/15 10/07 21 53
>
> 40 1971 0 0 0 30 08/23 11/01 8 71
>
> 41 1991 0 0 0 20 08/16 10/02 0 46
>
> 42 1960 0 0 20+ 20 08/05 09/07 0 34
>
> 43 1988 0 0 0 25 08/09 09/20 0 32
>
> 44 1964 0 0 0 5 08/13 09/20 0 39
>
> 45 1983 0 10 0 10 08/08 09/16 0 21
>
> 46 1970 0 0 5 0 08/06 09/14 0 32
>
> 47 1956 0 0 0 40 09/07 09/30 0 24
>
> 48 1969 0 0 0 30 09/07 09/18 5 12
>
> 49 1955 0 0 5 15 09/13 09/24 0 12

MOST SEVERE\-\-\--50 1975 5 0 5 0 NEVER NEVER 0 0

**TABLE 1 (CONT)**

Column 1 - Distance from Point Barrow northward to ice edge (10 Aug)

Column 2 - Distance from Point Barrow northward to ice edge (15 Sept)

Column 3 - Distance from Point Barrow northward to boundary of five
tenths ice concentration (10 Aug)

Column 4 - Distance from Point Barrow northward to boundary of five
tenths ice concentration (15 Sept)

Column 5 - Initial date entire sea route to Prudhoe Bay less than/

equal to five tenths ice concentration

Column 6 - Date that combined ice concentration and thickness

dictate end of prudent navigation

Column 7 - Number of days entire sea route to Prudhoe Bay ice free

Column 8 - Number of days entire sea route to Prudhoe Bay less
than/equal to five tenths ice concentration

**TABLE 2**

**FORECAST MEDIAN EXTREMES 2003 1953-2002 1953-2002**

INITIAL OPENING DATE-COASTAL

ROUTE TO PRUDHOE BAY^1^ 24 Jul 01 Aug 15 Jul-NEVER

LENGTH OF NAVIGATION SEASON 66 days 61 days 0 - 112 days

FINAL CLOSING DATE 07 Oct 06 Oct NA^2^-07 Nov

NUMBER OF DAYS ROUTE

ENTIRELY ICE FREE 39 days 30 days 0 days-92 days

[DISTANCE FROM POINT BARROW NORTHWARD TO]{.underline}:

ICE EDGE (10 Aug) 10 nmi 5 nmi 0 nmi-50 nmi

HEAVY PACK EDGE^3^ (10 Aug) 30 nmi 10 nmi 0 nmi-70 nmi

ICE EDGE (15 Sept) 90 nmi 35 nmi 0 nmi-165 nmi

HEAVY PACK EDGE (15 Sept) 120 nmi 75 nmi 0 nmi-240 nmi

> 1 Opening date based on the initial date that the entire

route from the Bering Sea to Prudhoe Bay may be navigated

in less than/equal to five tenths concentration of ice

cover.

> ^2^ No closing date in 1975 because the route never

opened.

> ^3^ Distance from Point Barrow to the five tenths or greater ice
> concentration boundary.

**REFERENCES**

Barnett, D.G., 1980. A Practical Method of Long-Range Ice

Forecasting for the North Coast of Alaska. Sea ice

Processes and Models (R. Pritchard, Ed.), Univ. of Washington Press,
Seattle, 402-409.

#  Drobot, S.D. and Maslanik J.A., 2002. A practical method 

> for long-range forecasting of ice severity in the Beaufort Sea.
> Geophysical Research Letters, Vol 29,
>
> No 8, p54-57.