Recurring Northward Flow Events in the East Greenland Current: A New Pathway for Atlantic Heat into the Arctic

Abstract. The East Greenland Current (EGC) is the main conveyor of cold, fresh Polar Water and sea ice from the Arctic Ocean through Fram Strait to the subpolar North Atlantic. Seven years of continuous mooring observations on the East Greenland continental slope at 79° N (2018–2025) reveal that whilst the EGC typically maintains a southward flow year-round, it is punctuated by periodic northward flow events on the upper continental slope. The majority are short-lived local events (lasting fewer than 5 days), consistent with mesoscale eddy activity. However, two prolonged deep-reaching events — in April–May 2019 (29 days) and May–June 2025 (at least 35 days) — were anomalous in their duration, intensity (i.e. exceeding the climatological mean by 2–3 standard deviations), and vertical coherence (down to at least 500 m depth). During both events, hydrographic observations show anomalous warm Atlantic-origin waters at depths typically occupied by cooler Arctic Atlantic Water, weakened vertical stratification, and temperature-salinity properties consistent with recent West Spitsbergen Current recirculation across Fram Strait. An extended mooring record at 78°50' N (2003–2019) identified a further 7 deep-reaching northward flow events, demonstrating that episodic northward flow is a recurring intrinsic feature of the EGC system rather than a recent phenomenon. A persistent sea-level pressure dipole with anomalous northward winds along the East Greenland margin is identified all strong deep northward flow events. It is proposed that this forcing drives a lateral reorganisation of the boundary current where anomalous eastward Ekman transport displaces the EGC core offshore whilst geostrophically adjusted flow on the inner slope produces a net northward current inshore. The anomalously warm AW at depth thus arises through northward advection of recirculating AW and upwelling over the slope. These anomalous flow events establish an episodic northward pathway for warm Atlantic-origin water with a potential advective reach of perhaps hundreds of kilometres beyond the mooring location — a previously unidentified pathway of Atlantic heat transport into the Arctic interior. The co-occurrence of the 2025 event with a record low sea-ice area in July in the northeast Greenland region suggests that these oceanic events influence regional sea ice variability through dynamic atmospheric export and ocean-ice interactions, though a direct causal link remains to be established. Whether these events represent rare features of a naturally variable boundary current system or early signals of ongoing change in the Arctic-Atlantic exchange remains an open question.