Preprints
https://doi.org/10.5194/egusphere-2025-4269
https://doi.org/10.5194/egusphere-2025-4269
04 Sep 2025
 | 04 Sep 2025
Status: this preprint is open for discussion and under review for Ocean Science (OS).

Characterising Marine Heatwaves in the Svalbard Archipelago and Surrounding Seas

Marianne Williams-Kerslake, Helene Reinertsen Langehaug, Ragnheid Skogseth, Frank Nilsen, Annette Samuelsen, Silvana Gonzalez, and Noel Keenlyside

Abstract. In the Arctic Ocean, satellite-based sea surface temperature data shows that marine heatwave (MHW) intensity, frequency, duration, and coverage have increased significantly in recent decades, raising concern for Arctic ecosystems. A high frequency (more than three events per year) of MHWs has been shown around the Svalbard Archipelago. Based on this, we investigate MHW trends around Svalbard at the surface and subsurface, using a regional reanalysis from TOPAZ (1991–2022). We find an increase in the frequency and duration of MHW events around the Svalbard Archipelago over the last decade. Furthermore, we observe an increase in MHW frequency and duration west of Svalbard, associated with a long-term rise in sea surface temperature in the region. Analysis of eight individual summer (June–September) MHW events lasting longer than 10 days in Svalbard West, indicated the presence of four shallow (≤ 50 m) and four deep (> 50 m) MHWs after 2010, with a mean duration of 29 days. Some events extended from Svalbard West into the Barents Sea. Heat budget analysis demonstrated a greater contribution of ocean heat transport compared to air-sea heat fluxes in driving the MHW events. Deep and shallow events were associated with ocean heat transport anomalies of up to 9 TW. This new understanding of MHW characteristics including their horizontal and vertical distribution is key to assessing ecological impacts.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.
Share
Marianne Williams-Kerslake, Helene Reinertsen Langehaug, Ragnheid Skogseth, Frank Nilsen, Annette Samuelsen, Silvana Gonzalez, and Noel Keenlyside

Status: open (until 30 Oct 2025)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
Marianne Williams-Kerslake, Helene Reinertsen Langehaug, Ragnheid Skogseth, Frank Nilsen, Annette Samuelsen, Silvana Gonzalez, and Noel Keenlyside
Marianne Williams-Kerslake, Helene Reinertsen Langehaug, Ragnheid Skogseth, Frank Nilsen, Annette Samuelsen, Silvana Gonzalez, and Noel Keenlyside
Metrics will be available soon.
Latest update: 04 Sep 2025
Download
Short summary
Marine heatwaves—periods of extreme ocean temperatures—are increasing globally, posing a threat to marine ecosystems. One region where a high number of marine heatwave events per year has been observed is around Svalbard. This study characterises past marine heatwave events around Svalbard, including their extent in terms of both distance and depth. We identified eight events in western Svalbard that were largely driven by the movement of warmer water into the region by ocean currents.
Share