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The overflow of cold water through the Faroe Bank Channel (FBC) is the densest water crossing the Greenland‐Scotland Ridge and the densest source for the Atlantic Meridional Overturning Circulation (AMOC). Here, we show that the overflow volume transport remained stable from 1996 to 2022, but that the bottom water warmed at an average rate of 0.1°C per decade, mainly caused by warming of deep waters upstream. The salinity of the overflow water has increased as a lagged and reduced response to the salinity increase seen in the upper‐layer source waters. Therefore, the potential density of the bottom water over the FBC sill shows no statistically significant trend. After entrainment of warmer ambient waters downstream of the FBC, the nonlinear density dependence upon temperature implies, however, that the overflow contributed water of reduced density to the local overturning and the deep limb of the AMOC. Plain Language Summary: As part of the Atlantic Meridional Overturning Circulation—often called AMOC—dense water is formed north of the subsea ridge between Greenland and Scotland. On its route southward at depth, the dense water has to cross this subsea ridge called the Greenland‐Scotland Ridge. The densest water flows through the deepest trench, which is the Faroe Bank Channel with a sill depth of 840 m. Here, the strength of the flow has been monitored since 1995 together with its temperature and salinity characteristics. While the strength of the flow has been stable throughout the monitoring period, the dense water in the Faroe Bank Channel has warmed and also become more saline. Despite the warming, the density of the water, which is determined by the combination of temperature and salinity, has remained nearly unchanged. After leaving the Faroe Bank Channel, the dense water intensively entrains and mixes with warmer surrounding water and forms a larger volume of water, termed Iceland‐Scotland Overflow Water, that feeds the AMOC. The density of this large volume is sensitive to warming. The observed warming of the dense water may, therefore, have implications for the AMOC and thereby on the regional as well as global climate. Key Points: Observed Faroe Bank Channel overflow strength has been stable from 1996 to 2022, but the overflow waters warmed in the recent two decadesConcurrent salinity increase prevented the bottom water density from decreasing significantly from the effect of warmingAfter entrainment downstream, the overflow contributed water of reduced density to global overturning due to non‐linear effects of warming [ABSTRACT FROM AUTHOR]

The inflow of warm and saline Atlantic water to the Arctic Mediterranean (Nordic Seas and Arctic Ocean) between Iceland and the Faroes (IF-inflow) is the strongest Atlantic inflow branch, in terms of volume transport, and associated with a large transport of heat towards the Arctic. The IF-inflow is monitored on a section east of the Iceland-Faroe Ridge (IFR) by use of Sea Level Anomaly (SLA) data from satellite altimetry, a method that has been calibrated by in situ observations gathered over two decades. Monthly averaged surface velocity anomalies calculated from SLA data were strongly correlated with anomalies measured by moored Acoustic Doppler Current Profilers (ADCPs) with consistently higher correlations when using the reprocessed SLA data released in December 2021 rather than the earlier version. In contrast to the earlier version, the reprocessed data also had the correct conversion factor required by geostrophy. Our results show that the IF-inflow crosses the IFR in two separate branches. The Icelandic branch is a jet over the Icelandic slope with average surface speed exceeding 20 cm s−1, but it is narrow and shallow with an average volume transport less than 1 Sv (106 m3 s−1). Most of the Atlantic water crosses the IFR close to its southernmost end in the Faroese branch. Between these two branches, water from the Icelandic branch turns back onto the ridge in a retroflection with a recirculation over the northernmost bank on the IFR. Combining multi-sensor in situ observations with satellite SLA data, monthly mean volume transport of the IF-inflow has been determined from January 1993 to December 2021. The IF-inflow is part of the Atlantic Meridional Overturning Circulation (AMOC), which is expected to weaken under continued global warming. Our results show no weakening of the IF-inflow. Annually averaged volume transport of Atlantic water through the monitoring section had a statistically significant (95 % confidence level) increasing trend of (0.12 ± 0.10) Sv per decade. Combined with increasing temperature, this caused an increase of 13 % in the heat transport, relative to 0 °C, towards the Arctic of the IF-inflow over the 29 years of monitoring. The near-bottom layer over most of the IFR is dominated by cold water of Arctic origin that may contribute to the overflow across the ridge. Our observations confirm a dynamic link between the overflow and the Atlantic water flow above. The results also provide support for a previously posed hypothesis that this link may explain the difficulties in reproducing observed transport variations of the IF-inflow in numerical ocean models, with consequences for its predictability under climate change. [ABSTRACT FROM AUTHOR]