Relationships between iceberg plumes and sea-ice conditions on northeast Devon Ice Cap, Nunavut, Canada

Abstract

This study investigates the impact of sea-ice conditions on the production of iceberg plumes from two tidewater glaciers on Devon Ice Cap, Nunavut, Canada. These effects are quantified using a 12 year RADARSAT-1 satellite record from 1997–2008 that contains imagery from approximately every 1–2 weeks in the winter and every 1–4 days in the summer. Iceberg plumes identified in this record are verified against terrestrial time-lapse photography of Belcher Glacier from 2007–08. Results suggest a strong relationship between iceberg plumes and the retreat of sea ice from the glacier termini, with the plumes caused by both the release of previously calved icebergs (ice melange) and new glacier calving. Iceberg plumes are also sometimes observed at other times in the summer and in midwinter (occasionally on both glaciers simultaneously), with these events likely due to new glacier calving alone. Analysis of tides and air temperatures suggests that they provide a minor influence on the timing of iceberg plumes. Instead, it appears that changes in the presence of sea ice are dominant on seasonal timescales, although internal glacier dynamics likely play a significant role for winter plume events that occur when substantial thicknesses of landfast sea ice are present.

Ice island deterioration

“…The reduction in Arctic sea ice extent increases the likelihood of open water adjacent to ice shelves and FITs (Copland et al, 2007;Zhang et al, 2013;IPCC, 2014). The decreased back-pressure exerted on these ice features leads to an increased susceptibility to calving, as does the reduced protection from ocean and wind driven waves (Herdes et al, 2012;Nick et al, 2013;Copland et al, 2017;Hill et al, 2017).…”

Iceberg production and characteristics around the Prince of Wales Icefield, Ellesmere Island, 1997-2015

“…SAR imagery provided the primary data source for identifying iceberg plume events as it enabled observation through clouds and at night, and rough surfaces such as freshly calved glacier ice appear bright due to high backscatter. This facilitates the detection of iceberg plume events as they can be distinguished against the darker signature of open water or old sea ice, even under summer melt conditions (Herdes et al 2012). Care was taken to ensure that only new plume events were identified; occasionally, a mélange of sea ice and previously calved icebergs can get blown back against a glacier terminus, but this type of situation is readily identifiable by its lower backscatter relative to new plume events.…”

“…There are many factors that control the stability of tidewater glaciers (Vieli and Nick 2011), but in the Arctic it seems that the presence of landfast sea ice and an ice mélange (mixture of sea ice and densely packed calved icebergs) at their termini influence terminus stability (Higgins 1991;Reeh et al 2001;Herdes et al 2012;Carr, Vieli, and Stokes 2013;Carr, Stokes, and Vieli 2014;Moon, Joughin, and Smith 2015;White and Copland 2019). Past research conducted predominantly on outlet glaciers in Greenland and the Russian Arctic have identified the buttressing effect of sea ice or an ice mélange on the terminus of a glacier by inhibiting iceberg calving (Reeh et al 2001;Amundson et al 2010;Christoffersen et al 2012;Carr, Vieli, and Stokes 2013;Carr, Stokes, and Vieli 2014;Moon, Joughin, and Smith 2015).…”

“…Previous work on tidewater glaciers in the CAA has primarily focused on their surface velocities and ice fluxes to the ocean (Williamson et al 2008;Van Wychen et al 2014Millan, Mouginot, and Rignot 2017), but little research has been undertaken on the physical processes controlling iceberg production. The main study for the CAA is that of Herdes et al (2012), who investigated the relationship between iceberg plume events (caused by glacier calving) and ice mélange conditions for Fitzroy and Belcher glaciers on NE Devon Island. When we refer to iceberg plume events, we mean a mixture of freshly calved glacier ice and the ice mélange in front of the glacier terminus that are produced when icebergs are calved.…”

“…Fresh iceberg plume events appear bright in synthetic aperture radar (SAR) scenes and are more easily distinguishable from the calving of singular icebergs and previously produced iceberg plume events. Herdes et al (2012) found that most iceberg plume events occurred during the open water season, soon after fast ice had broken up at the terminus. An iceberg plume event differs from sikussak (a mixture of multi-year landfast sea ice and icebergs) in that it does not necessarily contain sea ice and can occur in open water (Dowdeswell and Jeffries 2017).…”