1. in situ or Altimetry ? Arctic – Subarctic Ocean Fluxes focus topics:
Combining satellite altimetry and in situ observations to monitor transports of volume, heat, and salt in the Faroe Current   Bogi Hansen, Karin M. H. Larsen, Svein Østerhus
in situ or Altimetry ?
AGU, 2003
Greenland
Iceland
Shet-
land
Faroes
focus topics:
1. Representativeness of ocean observations
Arctic – Subarctic Ocean Fluxes
Nordic
Seas
0.9 Sv
Monitoring section
3.8 Sv
48%
Faroe Current
2.7 Sv
0.6 Sv
North Atlantic
Østerhus et al. (2019)
image:AGU 2003

2. Atlantic water on the monitoring section
Average temperature from 78 CTD cruises
Atlantic
35.0 psu
4°C
Arctic
ADCPs:

3. In situ observations
Iceland

4. Weekly averaged volume transport 1997-2013 based on in-situ observations
Satellite altimetry
Sea level difference across the flow

5. Comparison ADCP - Altimetry
> 70% volume transport
Correlation combined ADCP-Altimetry: 0.86
Correlation ADCP-Altimetry: 28-day averages
0.28
0.61
0.78
0.73
Atlantic water
0.16×
+0.43×
+0.17×
+0.24×
0.17
0.64
0.34
Correlation ADCP-ADCP: 28-day averages
ADCP obs.: 2706 days ≈ 94 values 28-day averages

6. Altimetry variations represent surface velocity
from Aviso+ MDT
NO NO NO NO
from ADCP & CTD
∆H(t) L
U0 (cm/s):
After calibration with ADCP & CTD observations,
Altimetry SLA-values give surface velocities
But, what about sub-surface velocities ????????

7. Vertical integral of ADCP velocity
Volume transport down to fixed depths can also be determined from altimetry, solely DA
Atlantic water
0.99
0.91
0.99
0.97
Correlation q(t) versus U(0,t)

8. Temperature from up to 95 CTD cruises
Standard CTD station
Average 4°C isotherm
Atlantic water
How much of the variance in the lower boundary of Atlantic layer can be explained by Altimetry
± Standard
deviation
Arctic
water
Bottom
temperature
17% 34% 42% 60% 48% 30% 25% 16% explained by Altimetry
50% explained by Bottom temp.

9. TEmperature Longterm Logging by BOttom Grounded Instrumentation
Acoustic modem
Battery capacity > 5 years
Temperature sensor

10. Transport time series of Faroe Current

11. We still need in situ observations to monitor the Faroe Current But, satellite altimetry reduces the need considerably, once calibrated by in situ observations  
AGU, 2003
Greenland
Iceland
Shet-
land
Faroes
Faroe Current
2.7 Sv
Funding agencies: The Danish Energy Agency as part of the Arctic Climate Support Programme.
& EU Horizon 2020 research and innovation programme under grant agreement No (Blue-Action).
image:AGU 2003