Abstract
Coring sediments in subglacial aquatic environments offers unique opportunities for research on paleo-environments and paleo-climates because it can provide data from periods even earlier than ice cores, as well as the overlying ice histories, interactions between ice and the water system, life forms in extreme habitats, sedimentology, and stratigraphy. However, retrieving sediment cores from a subglacial environment faces more difficulties than sediment coring in oceans and lakes, resulting in low yields from the most current subglacial sediment coring methods. The coring tools should pass through a hot water-drilled access borehole, then the water column, to reach the sediment layers. The access boreholes are size-limited by the hot water drilling tools and techniques. These holes are drilled through ice up to 3000–4000 m thick, with diameters ranging from 10–60 cm, and with a refreezing closure rate of up to 6 mm/h after being drilled. Several purpose-built streamline corers have been developed to pass through access boreholes and collect the sediment core. The main coring objectives are as follows: (i) To obtain undisturbed water–sediment cores, either singly or as multi-cores and (ii) to obtain long cores with minimal stratigraphic deformation. Subglacial sediment coring methods use similar tools to those used in lake and ocean coring. These methods include the following: Gravity coring, push coring, piston coring, hammer or percussion coring, vibrocoring, and composite methods. Several core length records have been attained by different coring methods, including a 290 cm percussion core from the sub-ice-shelf seafloor, a 400 cm piston core from the sub-ice-stream, and a 170 cm gravity core from a subglacial lake. There are also several undisturbed water–sediment cores that have been obtained by gravity corers or hammer corers. Most current coring tools are deployed by winch and cable facilities on the ice surface. There are three main limitations for obtaining long sediment cores which determines coring tool development, as follows: Hot-water borehole radial size restriction, the sedimentary structure, and the coring techniques. In this paper, we provide a general view on current developments in coring tools, including the working principles, corer characteristics, operational methods, coring site locations, field conditions, coring results, and possible technical improvements. Future prospects in corer design and development are also discussed.
Highlights
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Research on the sub-ice-shelf sediment cores is mainly focused on interpreting presence or absence of the ice shelf in the geological record, inferring the interaction between the sub-shelf and open-water marine environments [3], and obtaining boundary information about sub-ice shelf sedimentation [14,15]
The first Antarctic subglacial sediment vibrocorer, designed and built by JLU, aimed to address the technical gaps involved in obtaining long sediment cores
Summary
An access borehole should be drilled using the hot water drilling method. GJ.rMavari.tSactii.oEnnga.l2p01o9t,e7n, t1i9a4l energy [8] This corer was planned to be used in the subglacial Lake Ellsworth in the 2012–2013 season by passing through an access borehole approximately 36 cm wide and ~3000 m deep [36] to obtain old sediments. A ~10 cm long coarse gravel core from beneath Rutford Ice Stream drill site, where ice thickness was 2152 m during the 2018–2019 season [61], respectively This corer was deployed at several hot-water boreholes (~40 cm in diameter) at the Ekström ice shelf between November 2018 and January 2019 as part of the Sub-EIS-Obs project [45]. ((aa))SSttrruuccttuurree ooff tthhee BBAASS//UUWWIITTEECC mmaannuuaallllyy ooppeerraatteedd ppeerrccuussssiioonn ccoorreerr:: ((bb)) HHaammmmeerr lliiffttiinngg ssttaattee aanndd ((cc)) hhaammmmeerr lloowweerriinngg ssttaattee Another UWITEC percussion corer deployed in the Antarctic is the UWITEC KOL Kolbenlot percuTshsiisonBApSis/tUoWn cIoTrEeCr, ma caonmuamlleyrocipaelrpartoeddupcetrucusessdiofnorcloarkeer sweadsimuseendt cdourriinngg, twheor2k0i1n1g–2a0t 1d2epauthsstroafl snuommmoerre itnhathne1h4o0tm-w[a4t6er].dTrhililsin2gmprloojnecgt caot rLearrissemn CanaunadllyGeoopregreatVeIdicfreosmhetlhveesi.ceAstuortfaalcoef [16126]0. UUnnffoorrttuunnaatteellyy,, tthhiiss ccoorreerr hhaass nnoott yyeett bbeeeenn ddeeppllooyyeedd dduuee ttoo tthhee ssaammee rreeaassoonn [[5544]] cciitteedd ffoorr tthhee SSLLEE ggrraavviittyy ccoorreerr
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