| 30 Dec 2025
Atlantic Water flow through Fram Strait to the Arctic Ocean measured by repeated glider transects
Abstract. We present estimates of northward transport of Atlantic Water (AW) across a zonal transect at 77°15′ N using repeated ocean glider observations. Over three missions during autumn and winter of 2020–2022, 22 high-resolution sections were collected, enabling detailed characterization of circulation branches and volume transport. On average, the West Spitsbergen Current (WSC) and the Front Current each transport approximately 2.5 Sv of AW (Θ > 2°C, SA > 35.06 g kg-1) northward, yielding a combined flux of about 5 Sv toward the Arctic. Variability in transport and current structure is substantial and appears linked to atmospheric forcing. Case studies reveal that anomalous northward wind stress coincides with peak AW transport, roughly twice the seasonal mean, consistent with Ekman dynamics and elevated sea surface height along the coast. Conversely, strong southward wind stress weakens the WSC and nearly eliminates the Front Current. Recirculating Atlantic Water (RAW, Θ > 0°C, SA > 35.06 g kg-1) west of the Front Current is estimated to be about 1 Sv, but this does not capture the expected stronger recirculation transport further west, beyond the glider's target transect. These results highlight the capability of gliders to resolve variability in boundary currents that mooring arrays cannot capture. Extended seasonal coverage, including summer, is needed to assess transport variability under peak wind forcing.
Competing interests: Ilker Fer is a member of the editorial board of Ocean Science.
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Review of the manuscript: “Atlantic Water flow through Fram Strait to the Arctic Ocean measured by repeated glider transects”.
The manuscript presents repeated glider transects on the western slope of Svalbard in 2020-2022. From these transects, volume transport is estimated of the West Spitsbergen, the Front Current and the recirculation branches in Fram Strait at different seasons. Some episodes of anomalous volume transport are analyzed in more details within case studies to suggest process mechanisms behind the variability of the volume transport. The results of this manuscript, although not so novel, highlight how gliders can be used to complement mooring lines and hydrographic transects. This manuscript can then have a significant impact when it comes to planning of future fieldwork. The manuscript is well written, and the methodology seems robust. The figures are clear and self-explanatory. This manuscript should be accepted for publication after some minor revisions.
My main comment regarding the manuscript concerns the description of the case study. I find those very interesting; however I think it would be valuable to be able to add some statistics about the wind. How often do we see these northerly/southerly winds? How representative are the observations over a longer time? A time series of wind over the last 20 years for example, with quantification of the different events will be useful, and some statistics could then be provided on how often the different cases are expected to occur.
Minor comments:
Figure 1: Please move the inset with the small maps, so that we can see the entire coastline of Svalbard. That will help the reader to find out where the study is localized.
Figure 3: what are the light blue dots? They are the same for both panels, but it is not indicated what they represent.
Figure 7: Very nice figure! Would it be possible though to add some scale for volume transport? Or has it been normalized? Also, for guiding the reader I would suggest indicating clearly which sections are autumn and which ones are winter.