Abstract
Abstract. This paper presents a systematic record of multi-year
sea-ice thickness on the northern Canadian polar shelf, measured during the
autumn and early winter of 2009–2010. The data were acquired by submerged
sonar moored in the Penny Strait where they measured floes drifting south from
the notional “last ice area” until 10 December, when the ice stopped
moving for the remainder of the winter. Old ice comprised about half of the
1669 km long survey. The average thickness of old ice within 25 km segments
of the survey track was 3–4 m; maximum keels were 12–16 m deep. Floes with
high average draft were of two types, one with interspersed low draft
intervals and one without. The presence or absence of thin patches
apparently distinguished large floes formed via the aggregation of smaller
floes of various ages and deformation states from those of a more homogeneous
age and deformation state. The former were larger and of somewhat lower mean
thickness (1–5 km; 3.5–4.5 m) than the latter (400–600 m; 6.5–14 m). A
calculated accretion of new ice onto the multi-year floes measured in the
autumn of 2009 was used to seasonally adjust the observations to thicknesses
expected by late winter, when comparative data were acquired in the 1970s.
The adjusted mean thickness for all 25 km segments with 4/10 or more old
ice was 3.8 m (sample deviation of 0.5 m), a value indistinguishable within
sampling error from values measured in the up-drift area during the 1970s.
The recently measured ice-draft distributions were also very similar to
those from the 1970s. These results suggest that the dynamical processes
that create very thick multi-year ice via ridging close to the study area
have been less influenced by climate change than the thermodynamic processes
behind the formation and decay of thinner level floes. The hazards posed by
such ice therefore persist regionally, although the risk has decreased with
the decrease in old-ice concentration during recent decades.
Subject
Earth-Surface Processes,Water Science and Technology
Cited by
5 articles.
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