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Observations of a cyclonic gyre in an ice-covered, midsize (, 5 km2), temperate lake are presented. Horizontal and vertical measurements of temperature and electrical conductivity measurements were collected using a conductivity–temperature–depth logger mounted on an autonomous underwater vehicle and additional instrumentation. These measurements revealed a cylindrical density anomaly with a radius of , 110 m extending from 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. The maximum azimuthal velocity, calculated assuming this balance, was , 2.1 cm s21 at 6–8 m depth. The Rossby number associated with this velocity was 1.7; this is consistent with the cyclogeostrophic assumption (i.e., Rossby number . 1) and nearly twice that of similar under-ice eddies in the Arctic Ocean. The estimated Ekman spindown timescale is 1.5–15 d, but despite this, the gyre appeared to be relatively unchanged over 6 d of field observations. This persistence implies the gyre was forced over the course of the field study; however, the source of the forcing is unknown. Horizontal temperature transects at and below the bottom of the gyre revealed coherent temperature fluctuations suggestive of vertical transport associated with the gyre.

Item Type:	Refereed Article
Research Division:	Engineering
Research Group:	Maritime engineering
Research Field:	Ocean engineering
Objective Division:	Environmental Management
Objective Group:	Management of Antarctic and Southern Ocean environments
Objective Field:	Antarctic and Southern Ocean oceanic processes
UTAS Author:	Forrest, AL (Dr Alexander Forrest)
ID Code:	82237
Year Published:	2013
Web of Science® Times Cited:	20
Deposited By:	NC Maritime Engineering and Hydrodynamics
Deposited On:	2013-01-22
Last Modified:	2013-06-18
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