Wintertime Expansion and Contraction of the Terra Nova Bay Polynya
151
went dramatic réductions. In contrast, the winter of 1989 saw a significant drop in
open water fraction in mid April and then a steady increase in open water fraction through December 1989. The winter of 1990 was characterized by generally
lower (-15%) open water fraction than in the previous 2 years. Explaining both
the low frequency wintertime fluctuations and the superimposed high frequency
fluctuations in open water fraction is the primary focus of this study.
3 Polynya Model
In an attempt to explain the observed fluctuations in open water fraction, Pease’s
one;dimensional, wind-driven Coastal polynya model [10] is considered. The
model is based on an assumed balance between the offshore advection of the Consolidated ice edge by the wind and ice production in the polynya, which tends to
close the polynya. This balance can be represented mathematically by:
DL(t)
Dt
P(r)L(t)
H,
= U^t),
(D
where Hl is the thickness of the Consolidated ice at the ice edge (taken here to be
0.1 m), L(t) is the width of the polynya,
is the offshore advection speed of the
Consolidated ice (here taken to be 3% of the wind speed measured at 10-m height
[35]), and P(t) is the total ice production rate given by:
p(t) = -^.
(2)
P,Lf
QNet(f) is the net heat flux to the atmosphère, p, is the density of ice (0.95X103 kg
m’3), and Lyis the latent heat of fusion (3.34X105 J kg1) [7].
Equation (1) can be integrated numerically using an Euler intégration scheme
[36] for specified forcing when initialized for the three individual winter periods
using the maximum polynya width:
(3)
[10, 37], where t0 is the initial time for the model run (May 1, 00:00 h for each
year).
4 Model Results
4.1 Régression Analysis
To minimize the impact of uncertainty in cloud cover and albedo estimâtes on the
results of this study, attention has been restricted to the winter months of May
151
went dramatic réductions. In contrast, the winter of 1989 saw a significant drop in
open water fraction in mid April and then a steady increase in open water fraction through December 1989. The winter of 1990 was characterized by generally
lower (-15%) open water fraction than in the previous 2 years. Explaining both
the low frequency wintertime fluctuations and the superimposed high frequency
fluctuations in open water fraction is the primary focus of this study.
3 Polynya Model
In an attempt to explain the observed fluctuations in open water fraction, Pease’s
one;dimensional, wind-driven Coastal polynya model [10] is considered. The
model is based on an assumed balance between the offshore advection of the Consolidated ice edge by the wind and ice production in the polynya, which tends to
close the polynya. This balance can be represented mathematically by:
DL(t)
Dt
P(r)L(t)
H,
= U^t),
(D
where Hl is the thickness of the Consolidated ice at the ice edge (taken here to be
0.1 m), L(t) is the width of the polynya,
is the offshore advection speed of the
Consolidated ice (here taken to be 3% of the wind speed measured at 10-m height
[35]), and P(t) is the total ice production rate given by:
p(t) = -^.
(2)
P,Lf
QNet(f) is the net heat flux to the atmosphère, p, is the density of ice (0.95X103 kg
m’3), and Lyis the latent heat of fusion (3.34X105 J kg1) [7].
Equation (1) can be integrated numerically using an Euler intégration scheme
[36] for specified forcing when initialized for the three individual winter periods
using the maximum polynya width:
(3)
[10, 37], where t0 is the initial time for the model run (May 1, 00:00 h for each
year).
4 Model Results
4.1 Régression Analysis
To minimize the impact of uncertainty in cloud cover and albedo estimâtes on the
results of this study, attention has been restricted to the winter months of May