Further study is needed to understand the mechanisms driving changes in CO2 seasonality

The gap

Evidence profile

Sourced from the future work and future-work section and stated challenges of the source papers, classified as general, spanning 2 journals.

Supporting evidence — 6 representative gaps

• Polar processes set Arctic marine heatwaves apart (2026) · Communications Earth & Environment · doi

  Fig. 4 | Impacts of Arctic MHWs. Conceptual summary of identified impacts of Arctic MHWs (bold text), suspected impacts through documented responses to anomalous warming (plain text), and effects remaining unclear (italics marked with a star) on components of the Arctic system plausibly sensitive to MHWs. Arctic- specific impacts are framed in gray. DMS: Dimethyl sulfide, CO2: carbon dioxide. during ice formation, can bring subsurface heat upward in regions influ- enced by Atlantic Water31, a process further enhanced by poleward winds promoting sea-ice export84,85. Its direct link to MHWs is, however, not yet established. The presence of subsurface heat, with no equivalent at lower latitudes, makes these processes particularly consequential in the Arctic and warrants dedicated investigation. Additional mechanisms can generate upward heat fluxes, although whether they produce anomalies of sufficient magnitude and persistence to drive MHWs remains unknown and is less likely. Planetary waves or Ekman pumping can vertically displace the thermocline, producing warm anomalies through upward heaving (in contrast to downward heaving typical of non-polar oceans18), but their effectiveness in the strongly salinity- stratified Arctic is uncertain. Tidal mixing over continental shelves, parti- cularly in Atlantic Water inflow regions, can also generate turbulent heat fluxes90.

  generalfuture work
  Keywords: arctic mhws impacts heat upward text subsurface regions atlantic water generate uxes anomalies heaving conceptual
• Polar processes set Arctic marine heatwaves apart (2026) · Communications Earth & Environment · doi

  Table 1 | Summary of the proposed scientific priorities for future Arctic MHW research, building on the knowledge gaps identified in this Perspective Scientific priorities 1. Characterize subsurface Arctic MHW statistics and vertical structure 2. Quantify the contribution of subsurface heat supply mechanisms to MHW onset 3. Quantify the net cloud effect on Arctic MHWs, from competing effects of increased moisture, shortwave–SST, and longwave–SST feedbacks 4. Quantify the net effect of ocean eddies on Arctic MHW onset and decay 5. Characterize the seasonality of Arctic MHWs statistics, drivers, and impacts 6. Attribute changes in Arctic MHW statistics to individual drivers and feedbacks under ongoing warming 7. Quantify the net impacts of Arctic MHWs on air–sea CO2 fluxes, from competing effects of sea-ice retreat and temperature-driven solubility changes 8. Document MHW ecological responses in high Arctic shelf seas, where the most severe events occur, but impacts remain poorly documented index145, which integrates intensity, duration, and areal extent, can complement the cumulative intensity alone and is less sensitive to Arctic SST variance than MHW categories57. Third, current MHW detection tracks only liquid ocean temperature, and is therefore blind to latent heat consumed by sea-ice melt—a term with no equivalent at lower latitudes. An energetic perspective treating the ice-ocean system as a whole could provide a relevant new angle for Arctic MHW research, complementing temperature-based approaches. Spatial characterization is also incomplete: the vertical structure of Arctic MHWs remains almost entirely uncharacterized. Only two studies have examined subsurface MHW conditions in the Arctic51,54 (Fig. 1a), despite evidence that subsurface events are as intense and more prolonged than surface ones17. The framework of Malan et al.18 offers the most com- plete vertical structure classification and is well-suited for Arctic application, pending one adjustment. The approach is designed for temperature- stratified oceans and uses the mixed layer depth and thermocline as refer- ence levels. In the salinity-stratified Arctic, the halocline is a more physically meaningful reference. Following Malan (personal communication, 2026), we recommend incorporating salinity or density profiles alongside tem- perature in the clustering algorithm to reflect the full thermohaline structure of the Arctic water column. Horizontally, Lagrangian and object-based detection approaches15 would provide more coherent characterizations and better capture interactions between warm water and sea ice at the ice edge.

  generalfuture work
  Keywords: arctic subsurface structure quantify mhws temperature statistics vertical ocean impacts scienti priorities perspective characterize heat
• Polar processes set Arctic marine heatwaves apart (2026) · Communications Earth & Environment · doi

  41. Gradinger, R. R. Adaptation of Arctic and Antarctic ice metazoa to 63. Oliver, E. C. Mean warming not variability drives marine heatwave 42. 43. their habitat. Zoology 104, 339–345 (2001). Bates, N. R., Moran, S. B., Hansell, D. A. & Mathis, J. T. An increasing CO2 sink in the Arctic Ocean due to sea-ice loss. Geophys. Res. Lett. 33, https://doi.org/10.1029/2006GL027028 (2006). Yasunaka, S. et al. An assessment of CO2 uptake in the Arctic Ocean from 1985 to 2018. Glob. Biogeochem. Cycles 37, e2023GB007806 (2023). trends. Clim. Dyn. 53, 1653–1659 (2019). 64. Deser, C. et al. Future changes in the intensity and duration of marine heat and cold waves: insights from coupled model initial-condition large ensembles. J. Clim. 37, 1877–1902 (2024). 65. Olonscheck, D., Mauritsen, T. & Notz, D. Arctic sea-ice variability is primarily driven by atmospheric temperature fluctuations. Nat. Geosci. 12, 430–434 (2019). 44. Qi, D. et al. Climate change drives rapid decadal acidification in 66. Ciavarella, A. et al. Prolonged Siberian heat of 2020 almost the Arctic Ocean from 1994 to 2020. Science 377, 1544–1550 (2022). impossible without human influence. Clim. Change 166, 9 (2021). 67. Hall, A. The role of surface albedo feedback in climate. J. Clim. 17, 45. Mohamed, B., Nilsen, F. & Skogseth, R. Marine heatwaves 46. characteristics in the Barents Sea based on high resolution satellite data (1982–2020). Front. Mar. Sci. 9, 821646 (2022). Smith, K. E. et al. Baseline matters: challenges and implications of different marine heatwave baselines. Prog. Oceanogr. 231, 103404 (2025). 47. Notz, D. & SIMIP Community. Arctic sea ice in CMIP6. Geophys. Res. 48. Lett. 47, e2019GL086749 (2020). Khosravi, N. et al. The Arctic Ocean in CMIP6 models: biases and projected changes in temperature and salinity. Earth’s Future 10, e2021EF002282 (2022). 49. Maynard, J. A. et al. ReefTemp: an interactive monitoring system for 50. coral bleaching using high-resolution SST and improved stress predictors. Geophys. Res. Lett. 35, L05603 (2008). Zhang, X. et al. Satellites reveal different stories of marine heatwaves in the sea-ice-covered pan-Arctic. Commun. Earth Environ. 6, 17 (2025). 51. Williams-Kerslake, M. et al. Characterising marine heatwaves in the Svalbard Archipelago and surrounding seas. Ocean Sci. 22, 587–607 (2026). 52. Wolf, K. K. et al. Heatwave responses of Arctic phytoplankton communities are driven by combined impacts of warming and cooling. Sci. Adv. 10, eadl5904 (2024). 53. Carvalho, K. S., Smith, T. E. & Wang, S. Bering Sea marine 54. 55. 56. heatwaves: patterns, trends and connections with the Arctic. J. Hydrol. 600, 126462 (2021). Lien, V. S., Raj, R. P. & Chatterjee, S. Surface and bottom marine heatwave characteristics in the Barents Sea: a model study. State Planet 4, 1–11 (2024). Zhang, X., Zheng, F. & Gong, Z. Regulatory factors and climatic impacts of marine heatwaves over the Arctic Ocean from 1982 to 2020. Int. J. Climatol. 44, 52

  generalfuture work
  Keywords: arctic marine ocean heatwaves heatwave clim geophys lett warming variability drives trends future changes heat
• Polar processes set Arctic marine heatwaves apart (2026) · Communications Earth & Environment · doi

  85. 86. 87. Fu, C. & Myers, P. G. Exceptional sea ice loss leading to anomalously deep winter convection north of Svalbard in 2018. Clim. Dyn. 62, 2349–2367 (2024). Pickart, R. S. et al. Upwelling on the continental slope of the Alaskan Beaufort Sea: storms, ice, and oceanographic response. J. Geophys. Res. Oceans 114, https://doi.org/10.1029/2008JC005009 (2009). Li, S. et al. Upwelling of Atlantic Water in Barrow Canyon, Chukchi Sea. J. Geophys. Res. Oceans 127, e2021JC017839 (2022). 89. 88. Cottier, F. R. et al. Wintertime warming of an Arctic shelf in response to large-scale atmospheric circulation. Geophys. Res. Lett. 34, https://doi.org/10.1029/2007GL029948 (2007). Koenig, Z. et al. Atlantic waters inflow north of Svalbard: insights from IAOOS observations and Mercator Ocean global operational system during N-ICE 2015. J. Geophys. Res. Oceans 122, 1254–1273 (2017). Fer, I. et al. Tidally forced lee waves drive turbulent mixing along the Arctic Ocean margins. Geophys. Res. Lett. 47, e2020GL088083 (2020). Aagaard, K. & Roach, A. T. Arctic ocean-shelf exchange: measurements in Barrow Canyon. J. Geophys. Res. Oceans 95, 18163–18175 (1990). 91. 90. 92. MacKinnon, J. A. et al. A warm jet in a cold ocean. Nat. Commun. 12, 93. 94. 95. 96. 97. 98. 2418 (2021). Karcher, M. J., Gerdes, R., Kauker, F. & Köberle, C. Arctic warming: Evolution and spreading of the 1990s warm event in the Nordic seas and the Arctic Ocean. J. Geophys. Res. Oceans 108, https://doi.org/ 10.1029/2001JC001265 (2003). Athanase, M. et al. New hydrographic measurements of the upper Arctic western Eurasian Basin in 2017 reveal fresher mixed layer and shallower warm layer than 2005–2012 climatology. J. Geophys. Res. Oceans 124, 1091–1114 (2019). Simon, A., Gastineau, G., Frankignoul, C., Rousset, C. & Codron, F. Transient climate response to Arctic sea ice loss with two ice- constraining methods. J. Clim. 34, 3295–3310 (2021). Polyakov, I. V. et al. Atlantification advances into the Amerasian Basin of the Arctic Ocean. Sci. Adv. 11, eadq7580 (2025). Timmermans, M. L. The impact of stored solar heat on Arctic sea ice growth. Geophys. Res. Lett. 42, 6399–6406 (2015). Truffer, M. & Motyka, R. J. Where glaciers meet water: subaqueous melt and its relevance to glaciers in various settings. Rev. Geophys. 54, 220–239 (2016). 99. Wekerle, C. et al. Atlantic Water warming increases melt below Northeast Greenland’s last floating ice tongue. Nat. Commun. 15, 1336 (2024). 100. Wood, M. et al. Ocean forcing drives glacier retreat in Greenland. Sci. Adv. 7, eaba7282 (2021). 101. Lenton, T. M. Arctic climate tipping points. Ambio 41, 10–22 (2012). 102. Rachold, V. et al. Nearshore Arctic subsea permafrost in transition. Eos Trans. Am. Geophys. Union 88, 149–150 (2007). 103. Shakhova, N. et al. Current rates and mechanisms of subsea permafrost degradation in the East Siberian Arctic Shelf. Nat. Commun. 8, 15872 (2017). 104. Hayashida, H. et al. Implications of sea-ice biogeochemis

  generalfuture work
  Keywords: arctic geophys ocean oceans response https atlantic water warming shelf lett warm commun loss north
• Future constraints and trends of the air-sea CO2 flux in the South-East Pacific region: a CMIP6 evaluation (2026) · Frontiers in Marine Science · doi

  Further study is needed to understand the mechanisms driving changes in CO2 seasonality. Additional research is required to address the uncertainties in the air-sea CO2 flux in the South-East Pacific. Future studies should aim to include more CMIP6 models and scenarios to improve the robustness of the results.

  generalfuture-work sectionevidence 5/5
  Keywords: further study needed understand mechanisms driving changes co2
• Wintertime organic carbon export provides a potential food source for zooplankton in the High Arctic (2026) · Communications Earth & Environment · doi

  Limited light availability and reduced microalgal production during winter make it challenging to study wintertime particulate organic carbon export. The remote and ice-covered location of the study area poses logistical challenges for data collection. The complexity of Arctic marine ecosystems makes it difficult to understand the ecological role of wintertime carbon export.

  generalstated challengesevidence 5/5
  Keywords: limited light availability reduced microalgal production during winter

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