Quaternary glaciation history and glaciology of Jakobshavn Isbræ and the Disko Bugt region, West Greenland: a review

Abstract

The Disko Bugt region in central West Greenland is characterised by permanent ice streams, of which Jakobshavn Isbræ is by far the most important. The first thorough studies on the glaciology of the region were conducted over 150 years ago by H.J. Rink, who introduced the terms 'ice streams' and 'Inland Ice'. Rink's work inspired new field work, which has continued to the present, and the long series of observations are unique for an Arctic region.
 Cooling during the Cenozoic led to ice-sheet growth in Greenland. A number of interglacial occurrences have been reported from the Disko Bugt region, and during the penultimate glacial stage, the Greenland ice-sheet margin extended to the shelf break. During the last glacial maximum, the ice margin probably extended only to the inner part of the banks on the continental shelf, and large floating glaciers may have been present at this time. During the Younger Dryas cold period, the ice margin may have been located at a marked basalt escarpment west of Disko Bugt.
 Disko Bugt was deglaciated rapidly in the early Holocene, around 10 500–10 000 years before present (10.5–10 ka B.P.), but when the ice margin reached the eastern shore of the bay, recession paused, and major moraine systems were formed. With renewed recession, the present ice-margin position was attained around 8–6 ka B.P., and by c. 5 ka B.P. the ice margin was located east of its present position. The subsequent Neoglacial readvance generally reached a maximum during the Little Ice Age, around AD 1850. This was followed by recession that has continued to the present day.
 The relative sea-level history shows a rapid sea-level fall in the early Holocene, and a slow rise in the late Holocene. This development mainly reflects a direct isostatic response to the ice-margin history.
 Jakobshavn Isbræ is the main outlet from the Greenland ice sheet. It drains c. 6.5% of the present Inland Ice, and produces c. 35–50 km3 of icebergs per year, corresponding to more than 10% of the total output of icebergs from the Inland Ice. The velocity of the central part of the ice stream at the front has been around 7 km/year since records began, but has nearly doubled in recent years. Other calf-ice producing glacier outlets in Disko Bugt produce c. 18 km3 per year. The large calf-ice production of Jakobshavn Isbræ may have been initiated at about 8 ka B.P. when the glacier front receded from the iceberg bank (Isfjeldsbanken) near Ilulissat. Ice streams in inner and outer Egedesminde Dyb may have been active during the early Holocene and during the last glacial maximum.

A 10Be chronology of early Holocene local glacier moraines in central West Greenland

“…Sample elevations range from 271 to 450 m a.s.l., well above the estimated 40–80 m a.s.l. marine limit for this area (Weidick & Bennike ). The average thickness was obtained for each sample in order to account for reduced 10 Be production with depth (Gosse & Phillips ).…”

“…Estimated marine limit elevation in this area is between 40 and 80 m a.s.l. (Weidick ; Weidick & Bennike ).…”

“…Regional map showing locations of 10 Be constraints on Gr IS retreat in our study area, the West Greenland ( WG ) Current (grey solid and dashed lines; modified from Perner et al . ()), and ice‐sheet moraines (modified with elements from Weidick & Bennike ()). Ice‐sheet moraine extents (black solid (mapped) and dashed (inferred) lines) are based on Weidick & Bennike ().…”

“…()), and ice‐sheet moraines (modified with elements from Weidick & Bennike ()). Ice‐sheet moraine extents (black solid (mapped) and dashed (inferred) lines) are based on Weidick & Bennike (). These ice‐sheet moraines include the Drygalski Moraines ( D ) and the Fjord Stade Moraines: the Marrait ( M , c. 9.3 ka) and Tasiussaq ( T , c. 8.2 ka) Moraines (Young et al .…”

Strange bedfellows: glacial diamictite and cap carbonate from the Marinoan (635 Ma) glaciation in Namibia

“…9). These depths are very modest compared with outlet fjords on Quaternary glaciated margins (Weidick & Bennike, 2007; Kessler et al. , 2008; Medvedev et al.…”