Kjetil Våge, UiB Bob Pickart, WHOI Mike Spall, WHOI Kent Moore, UoT H éðinn Valdimarsson , MRI
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Kjetil Våge, UiB Bob Pickart, WHOI Mike Spall, WHOI Kent Moore, UoT Héðinn Valdimarsson, MRI Dan Torres, WHOI Svetlana Erofeeva, OSU Jan Even Ø. Nilsen, NERSC Revised circulation scheme north of the Denmark Strait Blosseville coast, north of the Denmark Strait View from R/V Knorr, October 2008
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Revised circulation scheme north of the Denmark Strait. Kjetil Våge, UiB Bob Pickart, WHOI Mike Spall, WHOI Kent Moore, UoT H éðinn Valdimarsson , MRI Dan Torres, WHOI Svetlana Erofeeva, OSU Jan Even Ø. Nilsen, NERSC. Blosseville coast, north of the Denmark Strait - PowerPoint PPT Presentation
Transcript of Kjetil Våge, UiB Bob Pickart, WHOI Mike Spall, WHOI Kent Moore, UoT H éðinn Valdimarsson , MRI
Kjetil Våge, UiBBob Pickart, WHOIMike Spall, WHOIKent Moore, UoTHéðinn Valdimarsson, MRIDan Torres, WHOISvetlana Erofeeva, OSUJan Even Ø. Nilsen, NERSC
Revised circulation scheme north of the Denmark Strait
Blosseville coast, north of the Denmark StraitView from R/V Knorr, October 2008
from Hansen et al.(2010)
1 Sv = 106 m3/s
from www.whoi.edu
Exchange across the ridge Crucial part of climate system Denmark Strait
Largest overflow plume Arctic freshwater export
the Denmark Strait
from www.whoi.edu
- a choke point in the overturning circulation
Revised circulation scheme north of the Denmark Strait- the Greenland-Scotland Ridge
Revised circulation scheme north of the Denmark Strait- overturning circulation schemes
Transformation within boundary current loop (Mauritzen, 1996)
Revised circulation scheme north of the Denmark Strait- the North Icelandic Jet – another source of overflow water?
from Jónsson and Valdimarsson (2004)
Revised circulation scheme north of the Denmark Strait- overturning circulation schemes
Transformation within boundary current loop (Mauritzen, 1996)
Transformation within interior loop (Våge et al., 2011)
Roughly equal contribution from either source
Bathymetry north of the Denmark Strait- the Blosseville Basin
East Greenland Current (EGC)
North Icelandic Jet (NIJ)
Two currents advecting overflow water into the Denmark Strait
Inflow into the Denmark Strait- present state of knowledge
EGC NIJ???
Greenland Iceland
Mean absolute geostrophic velocity at Kögur computed from 4 realizations
σθ = 27.8 kg/m3
θ = 0oC
Observed circulation at the Kögur transect- an unknown current in the interior Blosseville Basin
EGC: East Greenland CurrentNIJ: North Icelandic Jet
shelf break
EGC NIJ
Greenland Iceland
separated
EGC
θ = 0oC
σθ = 27.8 kg/m3
Observed circulation at the Kögur transect- the separated East Greenland Current
Mean absolute geostrophic velocity at Kögur computed from 4 realizations
East Greenland Current (EGC)
North Icelandic Jet (NIJ)
Inflow into the Denmark Strait- revised circulation scheme
Mean properties at the Kögur transect
EGC: East Greenland CurrentNIJ: North Icelandic Jet
PSW: Polar Surface WaterAW: Atlantic Water
Nearly ¼ of the EGC system FW transport takes place in the interior
Reference salinity = 34.8
Transport estimates- Freshwater
Nearly ¼ of the EGC system FW transport takes place in the interior
The majority of the OW approaches the strait along the Iceland slope
Reference salinity = 34.8
0.8 ± 0.3 Sv 1.3 ± 0.4 Sv 1.4 ± 0.3 Sv
Total: 3.5 Sv
Transport estimates- Overflow water
Dynamic height of sea surface relative to 500 db
Iceland Sea gyre
EGC
shelf break EGC
separated EGC
Historical hydrography- Upper ocean circulation
Potential temperature Salinity
Vertically averaged between 50-100 m (potential temperature) and 10-30 m (salinity)
Historical hydrography- Near-surface layer
MITgcm Channel oriented along the east coast of Greenland Southern outflow becomes northern inflow Salinity restored to initial conditions in the northern end (32 at the surface on the shelf, 35 in the deep interior), temperature is constant 1 km horizontal resolution, 30 vertical levels Forced by steady annual mean wind stress
Numerical simulations- Model domain
Sharp gradient near the shelf break at high latitudes supporting a shelf break jet Offshore diversion of freshwater near y = 500 km
Numerical simulations- Mean sea surface salinity over final 2 years of integration
Eddies and filaments dominate the Blosseville Basin Freshwater diversion from the shelf break is highly time dependent
Numerical simulations- Sea surface salinity on day 770
Numerical simulations- Temporal evolution of near-surface layer at y = 320 km
Southward flow inshore of x = 50 km Offshore salinity front near x = 120 km, coincident with southward flow The separated EGC arises from eddies that coalesce when encountering the Iceland slope
Numerical simulations- Eddy scenario
Revised circulation scheme north of the Denmark Strait
Revised circulation scheme north of the Denmark Strait
Revised circulation scheme north of the Denmark Strait
Revised circulation scheme north of the Denmark Strait
Revised circulation scheme north of the Denmark Strait
Revised circulation scheme north of the Denmark Strait
The research leading to these results has received funding from the European Union 7th Framework Programme (FP7 2007-2013), under grant agreement n.308299 NACLIM www.naclim.eu
Revised circulation scheme north of the Denmark Strait
