Limnology, sedimentology, and hydrology of a jokulhlaup into a meromictic High Arctic lake

A large ice-dammed lake drained catastrophically into Lake Tuborg, Ellesmere Island, beginning on 25 July 2003. Limnological, sedimentological, and hydrological parameters were recorded before, during, and after this event. For several weeks prior to the jokulhlaup, water overtopped the ice-dammed lake and flowed into Lake Tuborg's freshwater basin. A shallow sill separates the freshwater basin from a larger, deeper basin containing similar to 25 PSU (practical salinity units) salt water. The sill blocked underflows from entering the saltwater basin before the jokulhlaup. The icedammed lake drained completely and catastrophically when englacial or subglacial conduits developed, and a glacier portal formed 980 m from the Lake Tuborg shore, marking the beginning of the jokulhlaup. The level of Lake Tuborg increased by 7.6 m in 84 It. This jokulhlaup is the largest known to have occurred in the High Arctic, and the largest witnessed in Canada since 1947. Strata of very cold water flowed above the chemocline for about 14 km, from the sill to the southwest end of the lake. The cold strata turbulently mixed with underlying salt water, allowing for saltwater flocculation of suspended sediment, causing rapid settling. The saltwater layer very slightly freshened and cooled. Close to the sill, near-surface sediments derived from the jokulhlaup are coarse and laminated; however, no erosion occurred toward the distal end of the take, where a fining upward unit with a coarse base was deposited.