Reanalysis of the Iceland-Faroe inflow Bogi Hansen, Karin Margretha H. Larsen, Hjálmar Hátún and Svein Østerhus ICES WGOH, San Sebastian, March 2015

Iceland-Faroe inflow

Old method in situ CTD and ADCP (Hansen et al, 2003)

New method Combining Altimetry with CTD and ADCP Isoline (combined thermo and halo) CTD stations Altimetry points ADCPs Velocity profile

Average surface velocities Geostrophy Altimetry ADCP

The depth of the 4°C isotherm Temperature field is linked to the velocity field (Hátún et al, 2004) EOF analysis of the altimetry SLA – Modes 1 and 2 explain 95% of the variability Tried regression of observed isotherm depth on various combinations of surface velocities and PC1 and PC2 – Between 42 and 65% of variability explained by U k + PC1

Calculating transports Total transport: Konstant (to bottom or 600m) AW transport: To bottom or average isoline AW transport: To bottom or simulated isoline

Average transport: 3.8 Sv Trend: 0.016±0.015 Sv yr -1 AW transport Weak seasonal variation Amplitude < 10% of avg transport

Simulating the temperature distribution T res : variance mainly associated with thermocline movement T res simulated by multiple regression on: AW temperature and 4°C isotherm depth (N04 – N11) AW temperature and altimetry principal component (N02 – N03)

Explained var. Using observed AW tmp and isotherm depth Using simulated AW tmp and isotherm depth

Heat transport (relative to 0°C) Average heat transport: 124±12 TW Trend: 1.0±0.5 TW·yr -1 Increase in Relative Heat Transport ~ 18% over the 20 yrs 3 yr r.avg 1 yr avg

Average salt transport: kg·s -1 Trend: 32± kg·s -1 ·yr -1 Relative Salinity Transport more than doubled over the 20 year period 3 yr r.avg 1 yr avg Salt transport (relative to 34.95)

The research leading to these results has received funding from the European Union 7th Framework Programme (FP ), under grant agreement n NACLIM