the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 25 Feb 2026
Greenland tip jet and deep convection in the Irminger Sea: disentangling the roles of heat loss and wind stress
Abstract. The strength of the Atlantic Meridional Overturning Circulation (AMOC) depends on deep-water formation in the Subpolar Gyre, particularly in the Irminger Sea, where convection is strongly modulated by short-lived but intense Greenland tip jet. These mesoscale westerlies induce substantial surface heat loss and impose wind stress on the ocean, jointly influencing convective intensity. Using the high-resolution Parallel Ocean Program (POP) within the Community Earth System Model (CESM), we disentangle the thermal and mechanical effects of tip jet on mixed layer deepening through three ensemble experiments: full-forcing (heat loss + wind stress anomalies), heat-only, and wind-only, each compared to a climatological control run. All forced cases show a significant December–April deepening of the mixed layer relative to the control. The heat-only and full-forcing experiments produce similar mixed layer depth (MLD) increases (+1200 m; reaching ~1800 m), confirming that surface heat loss is the primary driver of deep convection. The wind-only case shows a smaller but still significant increase (+400 m; MLD ~1000 m), associated with enhanced early-winter mixing and wind-driven salinity increases in the upper ocean. This wind stress forcing erodes the fresh surface layer, reduces buoyancy, and promotes shear-driven mixing in December so that climatological winter heat loss can deepen the mixed layer more efficiently. Because wind stress is not projected to weaken under future warming, its mechanical influence may help delay or modulate the decline of convection in the Irminger Sea as surface heat loss decreases.
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- RC1: 'Comment on egusphere-2026-918', Anonymous Referee #1, 18 Mar 2026
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RC2: 'Comment on egusphere-2026-918', Anonymous Referee #2, 20 Apr 2026
Review of “Greenland tip jet and deep convection in the Irminger Sea: disentangling the roles of heat loss and wind stress” by Fedorov et al.
The authors present an idealised ocean modelling study to assess the role of the westerly Greenland tip jet on the Irminger Sea region. Tip jets are added to control (CORE) atmospheric forcing fields by adding a perturbation to the surface sensible heat flux, the surface momentum or both (full forcing) that is based on a simple definition of westerly tip jets and ERA5 fields. The surface latent heat flux is not changed in this study. The findings clearly show the sensible heat flux is the primary driver of mixed-layer deepening, but the surface stress also plays a role in early winter ML deepening.
Overall, this is a well-constructed study, clearly written and illustrated. The diagnostics focus on mixed-layer depth responses to the forcing. With some additional figures delving into the mixing response via shear and Richardson number. The findings are not really unexpected but confirm what others have discussed in observational studies or studies using 1D ML models. I only have one major concern, which can be readily addressed and also I make a few minor suggestions.
Major point
Tip jets also perturb the surface latent heat flux, primarily because of the enhanced near-surface winds. This effect is neglected in this study, as mentioned. However, there is no discussion of any ramifications of this decision. If anything, adding in a LHF component will increase the effect of tip jets on the ocean in terms of deepening the mixed layer. I would recommend adding a few sentences on this point.
Specific Points
Line 13, I’d recommend adding “…Greenland tip jet wind events” to the end of the first sentence of the abstract, given this is an oceanic journal.
Lines 30-60 – there is a good introduction to the role of westerly Greenland tip jets in forcing the ocean where I think most of the key points are made and key references cited. However, there is no mention of easterly tip jets in the introduction. Easterly (or reverse) Greenland tip jets occur almost as frequently and impact the western Irminger Sea and the SE Labrador Sea (e.g. Moore and Renfrew 2005). They have been observed with research aircraft (Renfrew et al. 2009) and their dynamics explained both in broad terms (Moore and Renfrew 2005) and in detail for selected cases (Outten et al. 2009). Their impact on the ocean has been assessed via 1-D modelling (Sproson et al. 2008). I think this introduction should include 2-3 sentences on these phenomena, given their relevance to the subpolar North Atlantic.
Note: the area of deep ML in the SE Labrador Sea seen in the control run (Figure 2 bottom row) is investigated in Sproson et al. (2008).
Lines 235-242 – Figure 3d demonstrates that even the wind stress only experiments see considerable buoyancy change over the year (B_ocean), despite not having any tip jet heating forcing. This buoyancy loss must be coming from firstly the control heat loss (SHF+LHF) plus radiative heat loss at the surface (presumably from longwave heat loss in the main). It may be worth a comment on this point. At the moment there isn’t really an explantion here.
Lines 310-335 – in discussing the wind stress only forcing and the impact on ocean shear and Richardson number, the authors may be interested in looking over Zhou et al. (2018) – although focused on a different area, this study also partitions heat and momentum forcing and looks in detail at MLD changes. They also clearly show wind forcing deepens the ML, corroborating your findings.
References
Outten S.D., I.A. Renfrew, and G.N. Petersen, 2009: An easterly tip jet off Cape Farewell, Greenland. Part II: Simulations and dynamics, Quarterly J. Royal Meteorological Society, 135, 1934-1949. doi:10.1002/qj.531
Renfrew, I.A., S.D. Outten and G.W.K. Moore, 2009: An easterly tip jet off Cape Farewell, Greenland. Part I: Aircraft observations, Quarterly J. Royal Meteorological Society, 135, 1919-1933. doi:10.1002/qj.513
Sproson, D.A.J., I.A. Renfrew and K.J. Heywood, 2008: Atmospheric conditions associated with oceanic convection in the south-east Labrador Sea, Geophysical Research Letters, 35, L06601, doi:10.1029/2007GL032971
Zhou, S. X. Zhai, and I. A. Renfrew 2018: The impact of high-frequency weather systems on SST and surface mixed layer in the central Arabian Sea, J. Geophysical Research: Oceans, 123, doi: 10.1002/2017JC013609
Citation: https://doi.org/10.5194/egusphere-2026-918-RC2 -
EC1: 'Comment on egusphere-2026-918', Karen J. Heywood, 22 Apr 2026
I am very grateful to both reviewers for their detailed and constructive reviews, and for their suggestions for strengthening the manuscript. I hope that the authors will be able to take these comments onboard. I look forward to receiving their responses and to a revised manuscript.
Please respond here in the open online discussion. You do not have to have made all the necessary changes at that stage. After you submit your responses here, you will then get another month or so to submit your revised manuscript, together with responses to the referees. These responses can be the same as you post online, or can be updated. If you require additional time at any stage please do not hesitate to ask.
Karen J Heywood (co-editor-in-chief)
Citation: https://doi.org/10.5194/egusphere-2026-918-EC1 -
AC1: 'Comment on egusphere-2026-918', Aleksandr M. Fedorov, 23 Apr 2026
Dear Reviewers and Editor,
On behalf of my co-authors, I would like to thank you for your detailed and constructive comments, as well as for your guidance throughout the review process. We appreciate the time and effort you have invested in improving our manuscript.
We will provide a detailed response to the comments, together with a revised version of the manuscript, within the next month.
Kind regards,
Aleksandr FedorovCitation: https://doi.org/10.5194/egusphere-2026-918-AC1
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- 1
The manuscript presents a detailed and well-structured analysis of the role of Greenland tip jets in driving mixed layer deepening and deep convection in the Irminger Sea. The authors employ a set of ensemble ocean model simulations to separate the contributions of surface heat loss and wind stress. They compare heat-only, wind-only, and full-forcing experiments against a climatological control. While the manuscript is clearly written and the analysis is comprehensive, I have a few comments regarding the limitations of the experimental framework and the associated results sensitivity. This is not a criticism, as limitations are inherent to modeling works. I don’t recommend running additional simulations that would be a significant amount of work, but I suggest better acknowledging these limitations. Overall, the manuscript is of good quality and addresses an important question in subpolar ocean dynamics. I look forward to reading a revised version.
Major Comments
1. The authors attribute the observed changes in mixed layer depth and convection specifically to tip jets. However, from my understanding, since the control run is forced with a smoothed climatological annual cycle that contains no high-frequency variability, the experiments as designed cannot distinguish the effect of tip jets specifically from the effect of any intense episodic atmospheric forcing event. Could the results simply reflect the ocean's response to high-frequency wind and heat flux variability in general, rather than to the particular spatial and temporal structure of tip jets? The authors could explain what makes tip jet forcing dynamically distinct from other intense weather events in the region, such as reversed tip-jets, or acknowledge more explicitly that their results may generalize beyond tip jets to high-frequency atmospheric forcing.
2. The study relies on a composite representation of tip jets, based on the strongest 10% of westerly wind events. However, recent studies (DuVivier and Cassano 2015, Coquereau et al., 2024) have demonstrated that tip jets exist in various forms, with distinct spatial structures, intensities, and frequencies. Some of these forms are more prevalent than the canonical type examined in this study. For instance, Coquereau et al. (2024) found that tip-jet-like events occur in an average of 12% of the time, which is approximately twice as frequent as the peak frequency of canonical events during the 2014-2015 period. This frequency increases to 42% in DuVivier and Cassano (2015), because more events are associated to tip-jets. It remains uncertain how the results would change if a more realistic distribution of wind events in general (and tip-jets specifically) considered.
I appreciated the effort made to quantify the uncertainty presented at the end of the discussion (around l. 399-400). The authors should also discuss how the idealized composite forcing may limit the generalizability of their conclusions, and how the importance of heat loss compared to wind stress could vary across the entire spectrum of tip jets. This could potentially lead to less extreme canonical events compared to the 2014-2015 period but an increase in the occurrence of other types of tip jets.
3. In the introduction, the authors state that “variations in wind stress can drive […] Ekman-driven freshwater export from the Greenland shelf near Cape Farewell.” In the literature, tip jets are indeed suspected to have an impact on this shelfwater export to the gyre (Duyck et al. 2022, Coquereau et al. 2024 …). However, in the modeling framework, the applied tip-jet pattern does not extend to the shelf and is confined to the deep ocean (Fig 1). This raises questions about how the results shown, where tip jets predominantly drive a salinification of the Irminger Sea, reconcile with these previous results. Does the modeling framework underestimate the shelf water export, or is this process negligible compared to the enhanced vertical mixing of the surface ocean induced by tip-jets?
4. The wind stress anomaly is applied within a confined region and gradually decreases to zero over a buffer zone. However, any lateral gradient in wind stress will cause Ekman divergence or convergence at the forcing boundary, potentially leading to spurious upwelling or downwelling that could affect the results. Have you checked for any systematic vertical velocity or MLD signal around your forcing area? Do you think this could impact your results?
Minor Comments
References
A. K. DuVivier, J. J. Cassano, Exploration of turbulent heat fluxes and wind stress curl in WRF and ERA- interim during wintertime mesoscale wind events around southeastern Greenland. J. Geophys. Res. 120, 3593–3609 (2015).
Duyck, E., Gelderloos, R., and de Jong, M. F.: Wind‐Driven Freshwater Export at Cape Farewell, J. Geophys. Res. Oceans, 127, https://doi.org/10.1029/2021JC018309, 2022.
Arthur Coquereau et al. ,Extreme wind events responsible for an outsized role in shelf-basin exchange around the southern tip of Greenland. Sci Adv 10,eadp9266(2024).DOI:10.1126/sciadv.adp9266