Author(s): Aleksey Shestov; Ase Ervik
Keywords: No Keywords
Abstract: Though ice ridges have been studied now for a few decades, they remain the hardest part of ice cover to be explored and taken into account in the ice mass balance and ocean–atmosphere heat exchange balance. At the same time, they often can play the role of design load in offshore structure projects. Thus, any attempt at gaining new knowledge in ice ridge physics is valuable. This work is dedicated to studies of four drifting ice ridges in the Arctic Ocean during May-June2015. A field group of SAMCoT researchers joined Norwegian Young sea ICE cruise (N-ICE2015) organized by Norwegian Polar Institute. Data collected during Leg 5 and Leg 6 of the N-ICE2015 expedition are presented and analyzed in regards to thermodynamic properties and states of ice ridges in this paper. Morphology mapping technic using 2-inch augers, coring technic and thermistor buoy deployment were used to study geometry, physical properties and temperature profiles of the ridges. Four studied ice ridges R1-R4 had different keel drafts varied from 3.3 to 10.8 m. Morphology mapping measurements of ridges were repeated with a time span of 7-10 days. During this period, ridges were subjected to high ocean flux and unconsolidated rubble at the bottom of their keels was melting considerably. Reduction in cross-section area varied from 8 to28%, while macroporosity of unconsolidated rubble in the keel reduced by values varied between9 and 36%. Thermistor buoys were deployed inside ridges R1 and R4. They demonstrated two different states of ice ridges typical for winter season and summer season respectively. In ridge R1, the temperature gradient was detected through a consolidated layer while below there was an isothermal profile. In ridge R4, there was almost isothermal profile through the whole ridge. In R1 ridge, the consolidated layer was clearly seen both by geometry mapping and temperature profile while, in R4 ridge, the consolidated layer was detected mainly by geometry mapping and also by melting rate extracted from temperature profile data.