1. Observed 80-Years of Climate Change in Baffin Bay: Facts, Fiction, and the NAO
Melissa Zweng and Andreas Münchow
College of Marine Studies
University of Delaware
AGU 12/10/2004

2. Surface Properties along 25-day USCGC Healy Ship Track
in 2003
Temperature
Nares Strait
Baffin Bay
Latitude
Labrador
Sea
Salinity
AGU 12/10/2004

3. Salinity maximum (below 100-m):
Uniform over slope and basin
Fresher towards north and on shelves
Temperature on salinity maximum:
Warm over Greenland slope
Largest gradients in Davis Strait
Cooling towards the north
West Greenland “Current”
BIO data
AGU 12/10/2004

4. Temporal Analysis method
Separate data into 200-m vertical depth bins
Average
each profile into 200-m vertical bins (weights CTD and bottle profiles more evenly)
all profiles for each year for each vertical bin (minimizes bias by years with many profiles over years with few profiles)
Linear regression analysis on each bin
Use Fofonoff (1979) method to estimate error
All error bars shown are 95% confidence intervals
Degrees of freedom = number of years of data - 2
AGU 12/10/2004

5. Labrador Sea salinity significant not significant 95% confidence
100-m
500-m
900-m
1500-m
2100-m
Labrador Sea salinity
significant
not significant
95% confidence
Trends are
1920
1960
2000
AGU 12/10/2004

6. Northern Labrador Sea (62N-66N):
Depth (km)
Significant freshening
above 1500-m
Depth (km)
Lazier (1995),
Dickson et al. (2002),
Curry et al. (2003),
Lozier (yesterday)
AGU 12/10/2004

7. Baffin Bay temperature
significant
not significant
95% confidence
Trends are
1920
1960
2000
AGU 12/10/2004

8. Significant freshening above 300-m
Baffin Bay (67N-80N):
Depth (km)
Significant warming
below 700-m
Depth (km)
Significant freshening
above 300-m
AGU 12/10/2004

9. Relation of warming to NAO
Deep Baffin Bay basin,
200-m vertical bin average
1-year temporal bin average
Correlation with NAO (1-year lead)
95% confidence
that r0 for
r95<r
AGU 12/10/2004

10. Winter Time North-Atlantic Oscillation Index
(NAO, explains <30% of variance)
(blue) period
may not tell the whole story
Non-dimensional number
Lanczos low-pass
filtered NAO in red
Year
AGU 12/10/2004

11. Properties averaged along isobaths east and west of the “talweg”
NAO > +0.5
NAO < -0.5
67-76N
density
Depth (m)
salinity
temperature
Baffin
Greenland
Baffin
Greenland
2.5
1.5
0.5
isobath (km)
2.5
1.5
0.5
isobath (km)
AGU 12/10/2004

12. Properties averaged along isobaths for NAO+ (red) and NAO- (blue)
(“meridional” averaging as isobath trend north-south)
2.5
1.5
0.5
isobath (km)
-0.5
-1.5
Greenland
Baffin
Density:
lighter off Baffin, heavier off Greenland
during NAO+ relative to NAO-
Salinity:
fresher off Baffin, saltier off Greenland
during NAO+ relative to NAO-
Temperature:
similar off Baffin, warmer off Greenland
during NAO+ relative to NAO-
AGU 12/10/2004

13. Significant warming in Baffin Bay below Davis Strait sill depth;
Conclusions:
Significant warming in Baffin Bay below Davis Strait sill depth;
Temperature fluctuations correlate with NAO in [ ] m depth range where warming occurs;
West Greenland Current most likely source of warming
Baroclinic surface circulation more intense during NAO+
AGU 12/10/2004