A cyclonic gyre in an ice-covered lake

• Published in: Limnology and Oceanography
• Main Authors: Forrest, AL, Laval, BE, Pieters, R, Lim, DSS
• Format: Article in Journal/Newspaper
• Language: English
• Published: Amer Soc Limnology Oceanography 2013
• Subjects: Engineering; Maritime Engineering; Ocean Engineering; Arctic; Arctic Ocean
• Online Access: https://doi.org/10.4319/lo.2013.58.1.0363; http://ecite.utas.edu.au/82237

Observations of a cyclonic gyre in an ice-covered, midsize (, 5 km2), temperate lake are presented. Horizontaland vertical measurements of temperature and electrical conductivity measurements were collected using aconductivitytemperaturedepth logger mounted on an autonomous underwater vehicle and additionalinstrumentation. These measurements revealed a cylindrical density anomaly with a radius of , 110 m extendingfrom the surface to , 14 m depth. The observed radius is smaller than the internal Rossby radius of deformation(, 200 m), which suggests a cyclogeostrophic balance between centripetal, Coriolis, and pressure forces. Themaximum azimuthal velocity, calculated assuming this balance, was , 2.1 cm s21 at 68 m depth. The Rossbynumber associated with this velocity was 1.7; this is consistent with the cyclogeostrophic assumption (i.e., Rossbynumber . 1) and nearly twice that of similar under-ice eddies in the Arctic Ocean. The estimated Ekman spindowntimescale is 1.515 d, but despite this, the gyre appeared to be relatively unchanged over 6 d of fieldobservations. This persistence implies the gyre was forced over the course of the field study; however, the sourceof the forcing is unknown. Horizontal temperature transects at and below the bottom of the gyre revealedcoherent temperature fluctuations suggestive of vertical transport associated with the gyre.