Geoscience Reference
In-Depth Information
Table 2 Comparison of volume transport estimates from combined GOCE, altimetry and in situ hydrog-
raphy to previous studies as well as estimates from simulation models for the Island-Faroe Ridge (IFR),
Faroe-Shetland Channel (FSC), NwAFC, NwASC in the Svinøy Section and the total Svinøy Section
Source
Data
Period
IFR
[Sv]
FSC
[Sv]
Svinøy [Sv]
NwAFC
NwASC
Total
The current study
GOCE ? Altim. ? hydr.
1993-2011
3.5
4.1
3.0
3.9
6.9
Mork and Skagseth
(
2010
)
Altim. ? hydr.
1993-2009
1.7
3.4
5.1
Skagseth et al. (
2008
)
Current meter
1995-2006
4.3
Orvik and Skagseth
(
2005
)
Curr. meters
1995-1999
4.2
Orvik and Skagseth
(
2003
)
Curr. meters
1998-2000
4.4
Orvik et al. (
2001
)
Curr. meters ? ADCP
? hydr.
1995-1999
3.4
4.2
7.6
Berx et al. (
2013
)
Altm. ? ADCP ? hydro
1995-2009
3.5
Østerhus et al. (
2005
)
Bottom ADCP ? hydr.
1999-2001
3.8
3.8
Hansen et al. (
2010
)
Bottom ADCP ? hydr.
1997-2008
3.5
Sandø et al. (
2012
)
MICOM model
1994-2007
4.7*
4.7
The current study
HYCOM model
1993-2007
1.8
1.5
2.0
0.6
2.6
The current study
MICOM model
1993-2007
3.5
6.9
3.5
5.0
8.5
The current study
ATL model
1993-2007
3.5
4.2
3.5
4.7
8.2
* Only from 1997 to 2007
5 Summary
In combination with in situ hydrographical data, surface drifters and current meter mea-
surements, coupled sea ice—ocean models and the latest GOCE-derived geoid and MDT
(Pail et al.
2011
), the paper has investigated the quality, usefulness and validity of the new
GOCE data for studies of the ocean circulation and transports in the Nordic Seas and Arctic
Ocean. Using the GOCE data from release number 3 (based on 12 months of GOCE data in
the time interval 1 November 2009 to 2014 April 2011), the gravity model from the direct
approach yields the computation of the GOCE- based geoid, and jointly with the DTU10
MSS data (based on the integration over the period 1993-2011, Knudsen et al.
2011
), the
MDT (MSS-G) representing the same 18-year integration period has been calculated. In
summary, the following key findings and results are highlighted:
1.
New knowledge of the shape and spatial pattern of the MDT is derived at a spatial
resolution of around 100 km and with an accuracy of around 4-5 cm which is superior
to previous existing MDTs for this region.
2.
Combined with the steric height estimated from hydrographic data, the pure barotropic
contribution to the MDT shows distinct features in consistence with known deep
barotropic circulations in the Norwegian and Greenland Seas.
3.
The new GOCE-based MDT and surface geostrophic currents compare favorably with
existing independent surface velocity calculations derived from combined altimeter
data, in situ observations and gravity field models.
4.
The transport estimates, both in the mean and seasonal signals, are also favoring the
combined use of the GOCE-based surface geostrophic current and hydrographic data.
