pathways of atlantic water
DESCRIPTION
Pathways of Atlantic Water. Cecilie Mauritzen – Norwegian Meteorological Institute. NOClim 2 Workshop, M/S Nordkapp, October 1 2003. Meridional overturning circulation. Water sinks. But this is not where it get dense. 60N. EQ. Greenland-Scotland Ridge. Entrainment. 6Sv. Dense, but - PowerPoint PPT PresentationTRANSCRIPT
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
Pathways of Atlantic Water
Cecilie Mauritzen – Norwegian Meteorological Institute
NOClim 2 Workshop, M/S Nordkapp, October 1 2003
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
Meridional overturning circulation
EQ 60N
Water sinks.But this is not
where it get dense
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
Greenland-Scotland Ridge
60N
700m
3000 m
Sin
kin
g
En
trai
nm
ent
Nordic Seas
Dense, but still shallow
6Sv
6Sv
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
Erika Dan 1962, o
Northward boundwarm water
Southward bound cold water
Velocity cores (”branches”)≠ distribution of warm water
Schematic
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
8-9 degrees in core
Faroe-Shetland Channel:Dense water fills 600m;
AIW, NSDWWarm water on slope
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
7-8 degrees in
core
Summer Winter
Svinøy (example from 1988)
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
Gimsøy (winter 1988)
6-7 degrees in core
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
Grand Banks
Rockall
Lofoten basin
Fram Strait
Eurasian Basin
Overflows (wide range)
In a budget: account for transports
and air sea fluxes
Cooling and significant freshening
Magical boundary
Enough water (7 Sv) istransformed to the right
density range
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
• Transformation in the warm Atlantic Current does not involve deep mixed layers. So whats up with the deep mixed layer sites, the Greenland and Iceland Seas?
• Attempts to quantify export of dense water from open-ocean deep convection sites result in small numbers (< 1 Sv). The tracer release experiment in the Greenland Sea (TRACTOR) showed qualitatively the same thing; it took for example two years before any dense water reached the overflows. I.e. not a BIG player.
• BUT: is it possible that there has been times when significant amounts of the Atlantic Water did take a shortcut through the Iceland or Greenland Seas?
Schematic
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
Air-Sea Heat Exchange
Air-sea heat fluxes not any larger in the Iceland and Greenland Seas than
in the rest of the Nordic Seas
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
Hydrographic Conditions in the Iceland Sea
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
Irminger Current
1992?
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
Conclusions
• Establishment of pathways requires quantification
• Get the most important players (say, 4 out of 5 Sverdrup)
• There has been very significant hydrographic changes in the Nordic Seas in the 20th century – need to establish whether the pathways may have changed, just as we need to establish whether the strength has changed.
• Stay tuned……slow detective work (and, getting access to the most useful data isn’t always so easy)
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
Moving into the Nordic Seas…
• Roughly 7 Sv warm water in• Roughly 1 Sv cold water in
• Roughly 3 Sv cold, light water out
• Roughly 5 Sv cold, dense water out
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
Typiske snitt – hvordan komme fram til sirkulasjonsbilde
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
Evolution of warm Atlantic Water:Cooling AND freshening!
Temperature Salinity
Grand Banks 12 35.5
Rockall 8 35.3
Norskehavsbassenget 7.5 35.2
Lofoten/Barents Sea 6.5 35.1
Arctic Ocean Entrance 3 35
Arctic Ocean 0.5 34.9
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
Svinøy section
Orvik and Skagseth 2002
Time series is short, but suggest time variability in volume flux of warm inflow water
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
Gimsøy
900 800 700 600 500 400 300 200 100 0
500
1000
1500
2000
2500
3000
3500
Distance [km]
Dep
th [
m]
34.91
34.905
35.1
33.2
34.7
34.8
34.85
34.88
34.9
34.905
34.91
34.912
34.913
34.92
34.95
35
35.1
35.2
35.25 552 541540 538 533 528 526 524 522 519 513
Salinity Gimsøy - North West
900 800 700 600 500 400 300 200 100 0
500
1000
1500
2000
2500
3000
3500
Distance [km]
Dep
th [
m]
-0.9
-0.8
0
-1.1
-1.05
-1
-0.9
-0.8
-0.5
0
0.5
1
2
3
4
5
6
7
8
9
10 552 541540 538 533 528 526 524 522 519 513
Potential temperature [oC]Gimsøy - North West
Norwegian Meteorological InstituteM/S Nordkapp Fall 2003
Schematic of the MOCHow do we determine the
pathways of water masses?