Interannual variability in hydrography and water mass distribution in Hornsund, an Arctic fjord in Svalbard

ABSTRACT

Progressing warming in the Arctic and increased extreme weather events can significantly influence the hydrography of Svalbard fjords, leading to changes towards more Atlantic-type waters in the fjords. In this paper, we look into the hydrographic conditions in Hornsund, the southernmost fjord on the west coast of Svalbard, by analysing high-resolution CTD measurements collected in July during cruises with the RV Oceania between 2001 and 2015. These observations revealed high interannual variability in temperature, salinity and distribution of water masses, mainly due to differences in timing of the transition between winter and summer conditions but also as a result of changing environmental factors such as air temperature and sea-ice cover. Hornsund shows weak Atlantic Water occupation, probably due to strong influence of the Sørkapp Current along the southern coast of Spitsbergen. The main basin of the fjord was much more influenced by waters entering the fjord from outside than the inner basin, Brepollen, which was mainly characterized by the presence of locally formed Winter Cooled Water (WCW). The amount and properties of WCW in Brepollen revealed high variability after 2006, and no WCW in July 2012. The results of our study show that Hornsund is highly variable and susceptible to recently observed atmospheric and oceanic extreme events in the Svalbard region.

KEYWORDS:

• Temperature
• salinity
• Atlantic Water
• Sørkapp Current
• Spitsbergen
• environmental factors

ABBREVIATIONS:

• ArW: Arctic Water
• AW: Atlantic Water
• CTD: conductivity, temperature and depth sensor
• DFI: days of fast ice
• IW: Intermediate Water
• LW: Local Water
• SC: Sørkapp Current
• SW: Surface Water
• TAW: Transformed Atlantic Water
• WCW: Winter Cooled Water
• WSC: West Spitsbergen Current

Acknowledgments

We thank the crew of the RV Oceania for assistance during measurements and all scientists, technicians and students who contributed to the collection of the impressive hydrographic database from Hornsund. We would like to also thank the Institute of Geophysics, Polish Academy of Science, and especially Tomasz Wawrzyniak, for providing meteorological data from the Polish Station in Hornsund. We thank Joanna Pardus for providing data for the basemap preparation and Ilona Goszczko for valuable comments and suggestions in an early version of the manuscript. Finally, we would like to thank three anonymous reviewers for very constructive comments and suggestions which significantly improved the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The main part of this study was supported by the statutory research funding, subject 1.4, carried out by the Institute of Oceanology, Polish Academy of Sciences, in Sopot. Additional financial support was received from the Polish–Norwegian project Arctic Climate System of Ocean, Sea Ice and Glacier Interactions in Svalbard (AWAKE-2; Pol-Nor/198675/17/2013). The largest part of the archival data was processed under the activity of the project Growing of the Arctic Marine Ecosystems (GAME), financed by the Polish National Science Center funds (grant no. DEC-2012/04/A/NZ8/00661). Publication costs were partially covered by funds from the Leading National Research Centre (KNOW), received by the Centre for Polar Studies for the period 2014-18.