  Detailed water kinematics are important for understanding
atmosphere-ice-ocean energy transfer processes in the Arctic. There are few in
situ observations of 2D velocity fields in the marginal ice zone. Particle
tracking velocimetry and particle image velocimetry are well known laboratory
techniques for measuring 2D velocity fields, but they usually rely on fragile
equipment and pollutive plastic tracers. Therefore, in order to bring these
methods to the field, we have developed a new system which combines a compact
open-source remotely operated vehicle as an imaging device, and air bubbles as
tracing particles. The data obtained can then be analyzed using image
processing techniques tuned for field measurements in the polar regions. The
properties of the generated bubbles, such as the relation between terminal
velocity and diameter, have been investigated under controlled conditions. The
accuracy and the spread of the velocity measurements have been quantified in a
wave tank and compared with theoretical solutions. Horizontal velocity
components under periodic waves were measured within the order of 10% accuracy.
The deviation from theoretical solutions is attributed to the bubble inertia
due to the accelerated flow. We include an example from an Arctic field
expedition where the system was deployed and successfully tested from an ice
floe. This work is an important milestone towards performing detailed 2D flow
measurements under the ice in the Arctic, which we anticipate will help perform
much needed direct observations of the dynamics happening under sea ice.
