On January 23rd Master of Science Eivind Hugaas Kolås successfully defended his PhD entitled “Atlantic water inflow into the Arctic Ocean: studies of pathways, transport and mixing processes using observations from ships and autonomous underwater vehicles”. In his PhD, Eivind described the pathways through which Atlantic Water enters the Barents Sea and the underlying mechanisms controlling this inflow. He studied the processes of heat loss and mixing of Atlantic Water with surrounding waters north of Svalbard and in the northwestern Barents Sea. Central in his PhD was the use of autonomous underwater vehicles (AUVs), which allows for the collection of data in remote (underwater) locations in challenging Arctic conditions.
Dr. Kolås work consisted of observational work on water masses, as well as technology development.
He studied the pathways through which Atlantic Water enters and circulates in the Arctic and the volume of this Atlantic Water that is transported along the continental slope north of Svalbard. He found that the strength of the Atlantic Water boundary current, which is a northeastward extension of the Gulf Stream, is sensitive to wind stress. Wind stress curls can double the volume of Atlantic Water that is transported through this current in less than a week. In addition, Kolås and his coworkers observed a previously undescribed, deep bottom-intensified current that flows parallel to the Atlantic boundary current between the 1500- and 2000-meter isobaths.
Photo: Ilker Fer, NERSC
Another part of his thesis focused on water in the northwestern Barents Sea that originated from the Atlantic and Arctic. He observed that about 0.9 Sv of Atlantic-origin water reaches the polar front region, (i.e., a region where cold polar water meets warmer water from lower latitudes). At the polar front Atlantic Water splits into several branches before diving underneath Polar Water. His study found that the amount of warm Atlantic water subducting under colder Polar Water is sensitive to the density difference north and south of the polar front, where relatively dense Atlantic Water leads to more Atlantic Water flowing northward.
In addition to studying the Atlantic Water inflow into the Arctic Ocean, Dr. Kolås also explored the potential of a light thruster-propelled AUV in regard to turbulence measurements. In collaboration with another PhD student, he assessed the data quality and potential limitations of a new setup to integrate microstructure sensors on the AUV.
Collectively, Kolås’ research improved our knowledge on Atlantic Water inflow in the Arctic Ocean through the Fram Strait and the Barents Sea, and sheds light on the mechanisms that control the inflow and mixing of Atlantic Water with surrounding waters.
Eivind Hugaas Kolås was supervised by Professor Ilker Fer (UiB) and co-supervised by Professor Frank Nilsen (UiB), Professor Martin Ludvigsen (NTNU) and Dr. Zoe Koenig (UiT). His evaluation committee consisted of Dr. Maria Dolores Pérez Hermandez from the University of Las Palmas de Gran Canaria, and Dr. Agnieszka Beszczynska-Möller from the Institute of Oceanology Polish Academy of Science.