Two new papers by EPOC researchers report findings on Arctic Atlantic Water; the warm, saline current that flows northward through the Fram Strait and drives heat exchange across the entire Arctic system. The papers, published in Deep Sea Research Part II: Topical Studies in Oceanography, are led by Rebecca McPherson (Alfred Wegener Institute (AWI)) and draw on EPOC’s long-term observational infrastructure in and around the Fram Strait.
The first paper presents a 27-year record of Atlantic Water temperature and salinity from a mooring array maintained continuously in the West Spitsbergen Current since 1997. The West Spitsbergen Current is the main route by which warm, saline Atlantic Water flows northward through Fram Strait into the Arctic Ocean, carrying heat that influences sea ice extent, marine ecosystems, and downstream ocean conditions across the Eurasian Basin.
The analysis identifies a long-term warming trend of 0.20°C per decade; a total increase of 0.54°C over the 27-year observational period. Within this trend, the record captures two distinct warm periods (2005 to 2007 and 2015 to 2017) and two cold periods (1997to 1999 and 2019 to 2024). The most recent cold anomaly persisted for over 5 years, more than twice as long as any previous cold event, and has not yet returned to the long-term mean. The paper also shows how these temperature anomalies propagate downstream into the Arctic interior, with signals reaching the Eurasian Basin ~6 years after passing through the Fram Strait.
Co-authors include Wilken-Jon von Appen (AWI), Laura de Steur (Norwegian Polar Institute), Torsten Kanzow (AWI), Agnieszka Beszczynska-Möller (Institute of Oceanology, Polish Academy of Sciences), and Angelika Renner (Institute of Marine Research, Norway).
Read the paper: McPherson, R., von Appen, W.-J., de Steur, L., Kanzow, T., Beszczynska-Möller, A., and Renner, A.H.H. (2026). Decades of change: Warming trends and hydrographic variability of Atlantic Water as observed in the west Spitsbergen Current (1997–2024). Deep Sea Research Part II, 227. https://doi.org/10.1016/j.dsr2.2026.105637
The second paper addresses a long-standing observational gap in Arctic science. Satellites can detect phytoplankton blooms at the ocean surface but cannot see through sea ice or resolve the vertical structure of the water column. Traditional moorings measure continuously but only at fixed depths, missing the fine-scale vertical detail that matters for understanding how biology, physics, and sea ice interact.
To fill this gap, the paper presents the first full-year deployment of a Subsea Winched Profiling System (SWIPS); a novel instrument developed at AWI that autonomously profiles the upper 125 metres of the ocean at high resolution, operating through both open water and ice-covered conditions. Deployed on the Yermak Plateau north of Svalbard, the profiler collected vertical profiles of temperature, salinity, oxygen, carbon dioxide, and chlorophyll.
The results reveal conditions that satellites and traditional fixed moorings would have missed entirely. In May 2023, the SWIPS detected a phytoplankton bloom beneath more than 80% sea ice cover, beginning more than a week before the onset of Polar Day (the day in the year when the Sun remains continuously visible for more than 24 hours). At peak bloom periods, satellite-derived chlorophyll estimates underestimated actual values by up to an order of magnitude, a finding with significant implications for how Arctic primary production is currently assessed from space.
The profiler also captured two episodes during winter 2023 in which warm, saline Atlantic Water reached the ocean surface, disrupting the expected cold, stratified winter conditions. Analysis of temperature-salinity profiles and satellite sea surface temperature maps indicates these anomalies were driven by upstream advection of Atlantic Water from the Fram Strait rather than local convection.
Co-authors include Normen Lochthofen, Simon F. Reifenberg, Wilken-Jon von Appen, and Hongyan Xi (all AWI).
Read the paper: McPherson, R., Lochthofen, N., Reifenberg, S.F., von Appen, W.-J., and Xi, H. (2026). Year-round vertically resolved observations of upper ocean hydrography and biogeochemistry in the Atlantic Water inflow north of Svalbard. Deep Sea Research Part II, 227. https://doi.org/10.1016/j.dsr2.2026.105639
Both papers are part of EPOC’s work on quantifying AMOC transport variability and the project’s Arctic research programme. The SWIPS deployment builds directly on EPOC’s biogeochemical sensor work described in our 2025 Fram Strait fieldwork report. The 27-year warming record in Paper 1 also connects to the wider EPOC objective of understanding how Atlantic Water properties change as they transit from the North Atlantic toward the Arctic, a critical component of the AMOC system.
Both papers appear in Volume 227 of Deep Sea Research Part II, published June 2026.