1. Processes and flow over the Iceland-Faroe Ridge
D2.3 Months 36
Partners: DMI (4 months), HAV, UHAM, MRI, UNIRES
Using results from a nationally (DK) funded experiment
and other observations on the Iceland-Faroe
Ridge, we will develop methods for improving simulations of
Iceland-Faroe warm-water poleward flow in ocean and
climate models, which have been shown to be biased.
Tentative conclusions
Based on new observations , overflow across the IFR must be considered of minor importance and likely on the order of 0.1 Sv.
Ocean climate models do not (?) reproduce observed volume transport variability of inflow across the IFR as monitored on a section north of the Faroes.
No established explanation exists for the model shortcomings that are also consistent with the new observations of a weak overflow.

2. New observations at the Western Valley of the IFR
Bogi, Karin, Steffen, Detlef, Kerstin, Svein

3. Observations at the Western Valley of the IFR
- Results from the field experiment (9 months deployments)
The average velocities in the core located only tens of meters above the bottom are weak, only 5cm/s.
The average volume transport of WV-overflow is less than 0.1 Sv.
These results were unexpected.

4. Inconsistency between models and observations at the IFR
Hypothesis:
The IF-overflow is linked to variations in IF-inflow through coupled sea-level and interface height changes.
Model IF-transport which per definition is the net transport compares with the true net volume transport: Atlantic inflow minus dense overflow
To explain apparent discrepancy between observed and simulated inflow the (unresolved) IF-overflow will have to be significantly weakened during the 2003 event.
Tentatively rejected

5. Question #1: Is the transport time-series at FN representative for the IF inflow?
Yes, qualitatively, in the model …. but exceptions exist ( ) and entrainment is high (1.3 Sv)!

6. Question #1: Is the transport time-series at FN representative for the IF inflow?

7. IW versus AW transport variability at section Faroe North
Open question #2
Model IW transport variability reflects the observed MNAW variability.
Model AW and IW variability is decoupled.
Can we explain why the two transports are decoupled in the model and (likely) coupled in nature?

8. Workplan (next six months):
Objectives
To substantiate the apparent discrepancy between modelled and observed transport variability.
To understand the nature of model limitations and the scope for improvements.
The focus at DMI will be on the EC-Earth climate model, ORCA1 and ORCA025 (highres), possibly higher resolution operational systems (DMI-HYCOM). Other contributions welcome (e.g. ORCA 1/12).
Task include
To assess the correspondence between heat and volume transport at the IFR and at the FN section: entrainment, modification by air-sea exchange, de-routing and time-delay (reservoir effects).

9. End

11. Inflow Overflow/Outflow
Østerhus et al., in prep.

12. Weak seasonality in the overflows (consistent with critical flow)
Seasonality links surface inflow the the east with light surface outflow to the west- the eusturine circulation loop.
Weak seasonality in the overflows (consistent with critical flow)
Observed DS overflow distribution is inconsistent with model result – suggests a high level of noise.
Overflow/Outflow Inflow
Østerhus et al., in prep.

13. The Blue-Action project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No