Glacial history and shoreline displacement on Erdmannflya and Bohemanflya, Spitsbergen, Svalbard

Submarine geomorphology is one of the main tools for understanding past fluctuations of tidewater glaciers. In this study we investigate the glacial history of Mohnbukta, on the east coast of Spitsbergen, Svalbard, by combining multibeam‐bathymetric data, marine sediment cores and remote sensing data. Presently, three tidewater glaciers, Heuglinbreen, Königsbergbreen and Hayesbreen calve into Mohnbukta. Hayesbreen surged at the end of the Little Ice Age, between 1901 and 1910. The submarine landform assemblage in Mohnbukta contains two large transverse ridges, interpreted as terminal moraines, with debrisflow lobes on their distal slopes and sets of well‐preserved geometric networks of ridges, interpreted as crevasse‐squeeze ridges inshore of the moraines. The arrangement of crevasse‐squeeze ridges suggests that both landform sets were produced during surge‐type advances. The terminus position of the 1901–1910 Hayesbreen surge correlates with the inner (R.2) terminal moraine ridge suggesting that the R.1 ridge formed prior to 1901. Marine sediment cores display 14C ages between 5700–7700 cal. a BP derived from benthic foraminifera, from a clast‐rich mud unit. This unit represents pre‐surge unconsolidated Holocene sediments pushed in front of the glacier terminus and mixed up during the 1901 surge. An absence of retreat moraines in the deeper part of the inner basin and the observation of tabular icebergs calving off the glacier front during retreat suggest that the front of Hayesbreen was close to flotation, at least in the deeper parts of the basin. As the MOH15‐01 core does not penetrate into a subglacial till and the foraminifera in the samples were well preserved, the R.1 ridge is suggested to have formed prior to the deposition of the foraminifera. Based on these data we propose that a surge‐type advance occurred in Mohnbukta in the early Holocene, prior to 7700 cal. a BP, which in turn indicates that glaciers can switch to and from surge mode.

Section: A Possible Early Holocene Glacier Advance In Mohnbuktamentioning

confidence: 80%

“…However, several Svalbard glaciers are suggested to have experienced pre‐LIA advances (Salvigsen et al . ; Ronnert & Landvik ; Werner ; Andersson et al . ; Hald et al .…”

Section: Discussionmentioning

confidence: 99%

Holocene glacial evolution of Mohnbukta in eastern Spitsbergen

Flink¹,

Hill²,

Noormets³

et al. 2017

“…comm. 2004) and Esmarkbreen advanced shortly after 9500+120 yr BP (T-6286; Salvigsen et al 1990). These glacier events are thought to be of short duration.…”

Section: Palaeoclimatic Implicationsmentioning

confidence: 99%

Faint traces of high Arctic glaciations: an early Holocene ice‐front fluctuation in Bolterdalen, Svalbard

Lønne¹

2005

Lønne, I. 2005 (August): Faint traces of high Arctic glaciations: an early Holocene ice-front fluctuation in Bolterdalen, Svalbard. Boreas, Vol. 34, Raised marine beach gravel at 62 m a.s.l. in Bolterdalen indicates that the inner part of Adventfjorden, central Spitsbergen, was ice-free shortly before 10 025+160 yr BP. A glacier advanced across the regressive, frozen beach terraces and into shallow water, 58 m above the present sea level, where a small wave-influenced icecontact delta was formed, 9775+125 yr BP. Maximum ice-front position was reached 9625+95 yr BP, 7 km outside the present ice margin. The advance was climatically forced and of several decades' duration, as seen from abundant molluscs growing in the prograding foreset beds. Today, the beaches appear as a continuous regressive sequence with no geomorphic evidence of the former ice margin. Sedimentological studies show, however, that a thin (1 m) deformation till was emplaced, the substrate was subglacially sheared to a depth of 1 m, and elongated clasts in the beach gravel were reoriented in an ice-flow parallel direction. The glacial deposits and structures, formed within 200 m from the ice front, highlight some important aspects of subglacial to ice-marginal processes in permafrost terrain. As the dead ice melted, the released debris was redistributed into thin sediment sheets down to 40 m a.s.l., which means that the postglacial meltwater-controlled reworking lasted c. 500 years. Similar isolated depocentra may be a key for future identifications of former ice margins at high latitudes.

“…ka BP(Salvigsen et al 1990;Lønne 2005). Glacier deposits labelled A-F corresponding to the T abreen, Albertbreen, Lyckholmdalen, Flowerbreen, Heftybreen and Richterbreen glaciers/valleys, respectively.…”

mentioning

confidence: 99%

Svalbard glaciers re‐advanced during the Pleistocene–Holocene transition

Farnsworth

Inǵólfsson

Retelle

et al. 2018

Despite warming regional conditions and our general understanding of the deglaciation, a variety of data suggest glaciers re-advanced on Svalbard during the Lateglacial-early Holocene (LGEH). We present the first well-dated end moraine formed during the LGEH in De Geerbukta, NE Spitsbergen. This landform was deposited by an outlet glacier re-advancing into a fjord extending 4.4 km beyond the late Holocene (LH) maximum. Comparing the timing of the De Geerbukta glacier re-advance to a synthesis of existing data including four palaeoclimate records and 15 other proposed glacier advances from Svalbard does not suggest any clear synchronicity in glacial and climatic events. Furthermore, we introduce six additional locations where glacier moraines have been wave-washed or cut by postglacial raised marine shorelines, suggesting the landforms were deposited before or during high relative sea-level stands, thus exhibiting a similar LGEH age. Contrary to current understanding, our new evidence suggests that the LGEH glaciers were more dynamic, exhibited re-advances and extended well beyond the extensively studied LH glacial expansion. Given the widespread occurrence of the LGEH glacier deposits on Svalbard, we suggest that the culmination of the Neoglacial advances during the Little Ice Age does not mark the maximum extent of most Svalbard glaciers since deglaciation; it is just the most studied and most visible in the geological record.