Observations of Wind in Nares Strait
There is incidental evidence that winds are strong … but how strong?
And why?
3 November 2006
01:06 UTC
Observations of surface wind are very sparse
Numerical simulation demonstrates that wind along the strait increases with end-to-end sea-level pressure drop
3 November 2006
00:00 UTC
High terrain in northern Canada & Greenland can facilitate a close juxtaposition of disparate SLP anomalies – here 41 mb
1974-1990
Primarily during late spring & summer
Only 2x per day
76W
72W
68W
64W
60W
56W
78N
79N
80N
81N
82N
83N
Lafayette BayC am p April 2005
Beaufort Lakes
C ape H erschel
D obbin Bay
Fort C onger
C arl R itter Bay
Lincoln Bay
P im Island
Scoresby Bay
PC S P C am ps, N ares S tra itLincoln Bay: 1974Beaufort Lakes: 1981Fort C onger: 1977-1979, 1981-1982Carl R itter Bay: 1978Scoresby Bay: 1983Dobbin Bay: 1985Pim Is land: 1990Cape H erschel: 1974-1989
Atkinson, D .E ., B . A lt and K . G a jew ski. 2000.A new da tabase o f H igh A rctic c lim ate da ta fromPolar C ontinenta l She lf P ro ject arch ives.Bu ll. A m er. M eteor. Soc. 81(11), 2621-2629.Surface weather has been
routinely observed by field teams operating from PCSP camps along Nares Strait
0 5 10 15 20 25 30 35 40W ind Speed (kt)
0.0
00
.05
0.1
00
.15
0.2
0
Rel
ativ
e fr
eque
ncy
of o
ccur
renc
e
1974 1976 1978 1980 1982 1984 1986 1988 1990
01
00
20
03
00
400
Nu
mb
er
of d
ata
1-Apr 1-M ay 1-Jun 1-Jul 1-Aug 31-Aug
04
08
01
20
160
20
0N
um
ber
of d
ata
PC SP C am ps, N ares S tra itLincoln Bay: 1974Beaufort Lakes: 1981Fort C onger: 1977-1979, 1981-1982Carl R itter Bay: 1978Scoresby Bay: 1983Dobbin Bay: 1985P im Is land: 1990Cape H erschel: 1974-1989
Atkinson, D .E ., B . A lt and K . G a jew ski. 2000.A new database of H igh A rctic c lim ate da ta fromPolar C ontinenta l She lf P ro ject arch ives.Bull. A m er. M eteor. Soc. 81(11), 2621-2629.
But no extreme winds were reported
Maximum 19 m/s
Rare above 15 m/s
Perhaps lack of strong winds reflects indolence?
Hall Expedition, Polaris Bay November 1871 – August 1871
Hall Expedition, Life Boat Cove
November 1872 – May 1873
Lady Franklin Bay Expedition
Fort Conger (Greely during IPY)
August 1881 – July 1883
24x per day 76W
72W
68W
64W
60W
56W
78N
79N
80N
81N
82N
83N
Lafayette BayC am p April 2005
Fort C ongerH all Land
Polaris Bay
Polaris H ouse
A lert
The only other observations were made by 19th century explorers at several over-wintering sites
1-M ay-72 1-Jun-72 1-Jul-72 1-A ug-72 1-S ep-72
010
20
30
40S
peed
(m
/s)
090
180
270
360
1-N ov-71 1-D ec-71 1-Jan-72 1-Feb-72 1-M ar-72 1-A pr-72 1-M ay-72
010
2030
40S
peed
(m
/s)
090
180
270
360
W ind at Po laris Bay1871 - 1872H ourly average
90 th percentile
D irection
0 10 20 30 40 50H ourly m ean speed (m /s)
010
2030
4050
Spe
ed o
n th
e ho
ur (
m/s
)
7 7 6 8 5 3
3 2 2 0
Wind topped 20 m/s once or twice per week, especially during the winter months
6 November 1871 to 31 August 1872
The maximum hourly speed was about 35 m/s (68 kt)… but stronger winds were missed for operational reasons
Polaris Bay
6 November 1871
to 31 August 1872
Strongest & most common winds blew along the strait
Speed histogram was strongly skewed < 5 m/s for 65% of the time> 20 m/s for 5%
0 10 20 30 40Speed on the hour (m /s)
0.0
00
.04
0.0
80
.12
0.1
6F
ract
ion
of d
ata
0 10 20 30 40H ourly average speed (m /s)
0.0
00
.04
0.0
80
.12
0.1
6F
ract
ion
of d
ata
0
45
90
135
180
225
270
315
10% 20% 30%
<=5
>5 - 15
>15 - 25
>25
0
45
90
135
180
225
270
315
0 10 20 30 40
Speed (m /s)M edian
M axim um
Most of the net atmospheric displacement occurred during winter
-50,000 -40,000 -30,000 -20,000 -10,000 0East (km )
-40,
000
-30,
000
-20,
000
-10,
000
0
Nor
th (
km)
15-N ov
30-N ov
15-D ec
30-D ec
14-Jan
29-Jan
13-Feb
28-Feb
14-M ar
29-M ar13-A pr
28-A pr
13-M ay28-M ay
12-Jun
27-Jun
12-Ju l
27-Ju l
11-Aug
26-A ug
6 November 1881 to
31 August 1882
Wind speed at Fort Conger, Discovery Harbour
Wind topped 20 m/s only twice in 2 years
15 August 1881
to 31 July 1883
1-Feb-83 1-M ar-83 1-Apr-83 1-M ay-83 1-Jun-83 1-Jul-83 1-Aug-83
05
10
15
20
Spe
ed
(m
/s)
09
01
80
27
03
60
1-Aug-82 1-Sep-82 1-O ct-82 1-N ov-82 1-D ec-82 1-Jan-83 1-Feb-83
05
10
15
20
Spe
ed
(m
/s)
09
01
80
27
03
60
1-Feb-82 1-M ar-82 1-Apr-82 1-M ay-82 1-Jun-82 1-Jul-82 1-Aug-82
05
10
15
20
Spe
ed
(m
/s)
09
01
80
27
03
60
1-Aug-81 1-Sep-81 1-O ct-81 1-N ov-81 1-D ec-81 1-Jan-82 1-Feb-82
05
10
15
20
Spe
ed
(m
/s)
09
01
80
27
03
60
The strongest winds were aligned with Nares Strait
Discovery Harbour15 August 1881to 31 July 1883
0 10 20 30 40H ourly average speed (m /s)
0.0
00
.04
0.0
80
.12
0.1
6F
ract
ion
of d
ata
0
45
90
135
180
225
270
315
10% 20% 30%
<=5
>5 - 10
>10 - 15
>15
0
45
90
135
180
225
270
315
0 10 20 30
S peed (m /s)M edian
M axim um
Direction histogram reflects local terrain
Speed histogram is strongly skewed < 5 m/s for 95% of the time
1-M ay-73 1-Jun-73 1-Ju l-73 1-A ug-73 1-S ep-73
01
02
03
0S
pee
d (
m/s
)
09
01
80
27
03
60
1-N ov-72 1-D ec-72 1-Jan-73 1-Feb-73 1-M ar-73 1-A pr-73 1-M ay-73
01
02
03
0S
pee
d (
m/s
)
09
01
80
27
03
60
0 10 20 30H ourly m ean speed (m /s)
01
02
03
0S
pee
d o
n th
e ho
ur
(m/s
)
Wind speed at Polaris House, Life Boat Cove
Wind topped 20 m/s infrequently, but low wind speed was uncommon
1 November 1872
to 31 May 1873
The wind regime was dominated by north-easterlies from Kane Basin
Polaris House1 November 1872to 31 May 1873
Strongest winds blow along the strait
Average wind speed is high
Speed histogram is bi-modal
0 10 20 30 40Speed on the hour (m /s)
0.0
00
.10
0.2
00
.30
0.4
0F
ract
ion
of d
ata
0 10 20 30 40H ourly average speed (m /s)
0.0
00
.05
0.1
00
.15
0.2
0F
ract
ion
of d
ata
0
45
90
135
180
225
270
315
20% 40% 60% 80%
<=5
>5 - 15
>15 - 25
>25
0
45
90
135
180
225
270
315
0 10 20 30 40
Speed (m /s)M edian
M axim um
Histograms of along-channel airflow suggests two regimes of wind
Atmospheric modeling has revealed strong correlation between along-strait airflow & SLP difference.
Samelson et al. (2006)
25 20 15 10 5 0 -5 -10 -15 -20 -25Pressure d ifference (m b)
0
50
100
150
200
250
-45 -35 -25 -15 -5 5 15 25 35 45Hourly average speed (m /s)
0
200
400
600
800
1000
1200
3.10 m b M ean7.33 m b S tnd dev'n
-0.5 m /s M ean 2.0 m /s S tnd dev'n
-7.0 m /s M ean10.0 m /s S tnd dev'n
W ind A long C hannel1871-1872
Pressure D rop A long C hannel2005-06
Alert minus Carey Islands
1) Light winds dominate to a degree varying with season & site
2) Occasional very strong winds follow the Strait
These observations suggest an important role for boundary-layer stability
The incidence of light wind at Polaris Bay was much higher than the likely incidence of weak along-channel pressure gradient
This suggests a non-linear response of surface wind to pressure forcing
The most likely cause of non-linearity under weak forcing is stable stratification of the atmospheric boundary layer
This prevalent condition is known as the Polar Inversion. Potential temperature may increase by 20°C in the lowest 300 m of the atmosphere
Contributing factors are atmospheric subsidence (adiabatic heating), cloud-free skies, strong long-wave radiative heat loss from the high emissivity snow-surface & weak insolation
The resulting stratification in potential density suppresses turbulence generated by shear in airflow near the ground
In consequence, momentum is not mixed down to the surface and ground-level wind remains light
Strong boundary-layer stratification decouples airflow aloft from surface friction (for a while)
Air flow through Nares Strait is not subject to geostrophic control on a synoptic scale
Suppression of boundary-layer turbulence permits continued acceleration of airflow aloft
Acceleration continues until shear production of TKE via free-stream instability (e.g. KH) overcomes buoyancy suppression
The atmospheric boundary then becomes turbulent, first intermittently and then explosively as eddies bring high-speed air to the surface
The implied sudden onset of extreme wind from calm is consistent with events at Lafayette Bay in April 2005
-9 -6 -3 0 3 6 9 12E lapsed tim e (hours)
010
20
3040
Spe
ed (
m/s
)
… and with a composite of windstorms measured at Polaris Bay during the winter of 1871-1872
Factors influencing the Polar Inversion affect the wind climate of Nares Strait
Snow cover (through surface emissivity)
Cloudiness (through down-welling long wave radiation)
Solar season
Lateral & vertical (viz. subsidence) advection of warm air aloft
Nares Strait may harbour a unique wind regime, by virtue of:
Its great length (550 km)
Its high relief (2000-3000 m)
Its strong boundary-layer stratification (Polar Inversion)
Its lack of a diurnal cycle in B-L stratification in winter