Spatial and seasonal variations of the snow chemistry at the central Filchner-Ronne Ice Shelf, Antarctica

Annals of Glaciology ◽

10.3189/1994aog20-1-283-290 ◽

1994 ◽

Vol 20 ◽

pp. 283-290 ◽

Cited By ~ 5

Author(s):

Andreas Minikin ◽

Dietmar Wagenbach ◽

Wolfgang Graf ◽

Josef Kipfstuhl

Keyword(s):

Sea Water ◽

Ice Cores ◽

Weddell Sea ◽

Sea Salt ◽

Ice Shelf ◽

Sulphur Compounds ◽

Annual Cycles ◽

Episodic Events ◽

Time Period ◽

Winter Time

The chemical stratigraphy of the surface firn of the central Filchner- Ronne Ice Shelf was determined in conjunction with stable isotopes from shallow firn cores and snow-pit samples collected at 1.1 widely distributed sites, and covering a time period of at least 20 years. The chemical analysis included ECM profiling and the determination of chloride, non-sea-salt (nss) sulphate, methanesulphonate (MSA), nitrate and, partly, sodium and bromide. Throughout the investigated area, winter time nss sulphate levels are found to be substantially negative, indicating that the sulphate to sodium ratio in airborne sea-salt particles is depleted by a factor of 5, approximately, in relation to the bulk sea-water ratio. While winter firn layers appear to be marked by episodic events of large sea-salt inputs, pronounced annual cycles with maxima in summer firn layers are commonly observed for the ECM signal and for nss sulphate, nitrate and MSA at all sites. For MSA, however, this phase relation is almost reversed for depths greater than 3-4m.The mean impurity levels consistently are strongly depleted with increasing distance from the ice edge by about 30% / 100 km for sea salt, 25% / 100 km for MSA and only 10%/ 100 km for nss sulphate. However, no substantial trend is observed for nitrate. It is concluded, therefore, that the sea-salt and the biogenic sulphur compounds deposited on the Filchner-Ronne Ice Shelf mainly originate from the adjacent Weddell Sea.Further important implications of the continental effects are: (a) an atmospheric residence time of nss sulphate apparently exceeding that of MSA probably due to the supplementary sulphate production on the ice shelf from biogenic SO2, and (b) a substantial limitation of the potential of deep ice cores already drilled on the Filchner- Ronne Ice Shelf in extracting reliable net temporal changes of sea-salt and biogenic sulphur species.

Reconnaissance of chemical and isotopic firn properties on top of Berkner Island, Antarctica

Annals of Glaciology ◽

10.3189/1994aog20-1-307-312 ◽

1994 ◽

Vol 20 ◽

pp. 307-312 ◽

Cited By ~ 9

Author(s):

D. Wagenhach ◽

W. Graf ◽

A. Minikin ◽

U. Trefzer ◽

J. Kipfstuhl ◽

...

Keyword(s):

Ice Core ◽

Depth Resolution ◽

Snow Accumulation ◽

Weddell Sea ◽

Sea Salt ◽

The South ◽

Ice Shelf ◽

Annual Cycles ◽

Ice Cap ◽

The North

The ice cap on Berkner Island is grounded on bedrock within the Filchner-Ronne Ice Shelf and is, therefore, expected to be a well-suited place to retrieve long-term ice-core records reflecting the environmental situation of the Weddell Sea region. Shallow firn cores were drilled to 11 m at the two main summits of Berkner Island and analysed in high depth resolution for electrical d.c. conductivity(ECM), stable isotopes, chloride, sulphate, nitrate and methane-sulphonate (MSA).From the annual layering of δD and non-sea-salt (nss) sulphate, a mean annual snow accumulation of 26.6 cm water at the north dome and 17.4cm water at the south domeare obtained. As a result of ineffective wind scouring indicated by a relatively lownear-surface snow density, regular annual cycles are found for all species at least in the upper 4-5 m. Post-depositional changes are responsible for a substantial decrease o[the seasonal δD and nitrate amplitude as well as for considerable migration of the MSA signal operating below a depth of 3-4 m. The mean chemical and isotopic firn properties at the south dome correspond to the situation on the Filchner-Ronne Ice Shelf at a comparable distance to the coast, whereas the north dome is found to be much more influenced by maritime air masses. Persistent high sea-salt levels in winter snow at Berkner Island heavily obscure the determination of nss sulphate probably due to sulphate fractionation in the Antarctic sea-salt aerosol. Estimated time-scale spredict ages at 400 m depth to be ~2000 years for the north and ~3000 years for the south dome. Pleistocene ice is expected in the bottom 200 and 300 m, respectively.

Reconnaissance of chemical and isotopic firn properties on top of Berkner Island, Antarctica

Annals of Glaciology ◽

10.1017/s026030550001661x ◽

1994 ◽

Vol 20 ◽

pp. 307-312 ◽

Cited By ~ 11

Author(s):

D. Wagenhach ◽

W. Graf ◽

A. Minikin ◽

U. Trefzer ◽

J. Kipfstuhl ◽

...

Keyword(s):

Ice Core ◽

Depth Resolution ◽

Snow Accumulation ◽

Weddell Sea ◽

Sea Salt ◽

The South ◽

Ice Shelf ◽

Annual Cycles ◽

Ice Cap ◽

The North

The ice cap on Berkner Island is grounded on bedrock within the Filchner-Ronne Ice Shelf and is, therefore, expected to be a well-suited place to retrieve long-term ice-core records reflecting the environmental situation of the Weddell Sea region. Shallow firn cores were drilled to 11 m at the two main summits of Berkner Island and analysed in high depth resolution for electrical d.c. conductivity(ECM), stable isotopes, chloride, sulphate, nitrate and methane-sulphonate (MSA).From the annual layering ofδD and non-sea-salt (nss) sulphate, a mean annual snow accumulation of 26.6 cm water at the north dome and 17.4cm water at the south domeare obtained. As a result of ineffective wind scouring indicated by a relatively lownear-surface snow density, regular annual cycles are found for all species at least in the upper 4-5 m. Post-depositional changes are responsible for a substantial decrease o[the seasonalδD and nitrate amplitude as well as for considerable migration of the MSA signal operating below a depth of 3-4 m. The mean chemical and isotopic firn properties at the south dome correspond to the situation on the Filchner-Ronne Ice Shelf at a comparable distance to the coast, whereas the north dome is found to be much more influenced by maritime air masses. Persistent high sea-salt levels in winter snow at Berkner Island heavily obscure the determination of nss sulphate probably due to sulphate fractionation in the Antarctic sea-salt aerosol. Estimated time-scale spredict ages at 400 m depth to be ~2000 years for the north and ~3000 years for the south dome. Pleistocene ice is expected in the bottom 200 and 300 m, respectively.

Ice-Ocean Interaction On Ronne Ice Shelf, Antarctica

Annals of Glaciology ◽

10.1017/s026030550000906x ◽

1990 ◽

Vol 14 ◽

pp. 341

Author(s):

A. Jenkins ◽

C.S.M. Doake

Keyword(s):

Cold Water ◽

Sea Water ◽

Freezing Point ◽

Accumulation Rate ◽

Weddell Sea ◽

Shear Stresses ◽

Strain Rates ◽

Horizontal Shear ◽

Ice Shelf ◽

Ice Stream

A detailed glaciological study of Ronne Ice Shelf has been undertaken along a flowline extending from Rutford Ice Stream grounding line to the ice front. Measurements of velocity, surface elevation, ice thickness, surface temperature and accumulation rate have been made at a total of 28 sites; at 17 of these ice deformation rates are also known. Although no direct measurements of basal conditions have been made, these can be deduced from observations made at the surface. Assuming the ice shelf to be in a steady state, the basal mass balance can be calculated at points where strain-rates are known. Information on the spatial distribution of basal saline ice layers can also be obtained from radio-echo sounding data. The derived pattern of basal melting and freezing influences both the ice shelf and the underlying ocean. Vertical heat advection modifies the temperature distribution within the ice shelf, which determines its dynamic response to driving and restraining forces through the temperature-dependent ice-flow law. Using measured strain-rates and calculated temperature profiles, the restraint generated by horizontal shear stresses can be derived for points on the flowline. It is the cumulative effect of these forces which controls the discharge of grounded ice from Rutford Ice Stream. Cooling of sea-water to its pressure melting point by melting of ice at depth has two important results. The outflow of cold, dense Ice Shelf Water, produced by this mechanism, is a major source of Antarctic Bottom Water, formed as it mixes at depth with the warmer waters of the Weddell Sea (Foldvik and Gammelsrod, 1988). If the cold water is forced up to shallower depths, frazil ice will be produced as the pressure freezing point rises, resulting in basal accretion if this occurs beneath the ice shelf.

First direct observation of sea salt aerosol production from blowing snow above sea ice

10.5194/acp-2019-259 ◽

2019 ◽

Cited By ~ 3

Author(s):

Markus M. Frey ◽

Sarah J. Norris ◽

Ian M. Brooks ◽

Philip S. Anderson ◽

Kouichi Nishimura ◽

...

Keyword(s):

Sea Ice ◽

Sea Water ◽

Open Ocean ◽

Weddell Sea ◽

Sea Salt ◽

Polar Regions ◽

Blowing Snow ◽

Snow Layer ◽

Sea Salt Aerosol ◽

Drifting Snow

Abstract. Two consecutive cruises in the Weddell Sea, Antarctica, in winter 2013 provided the first direct observations of sea salt aerosol (SSA) production from blowing snow above sea ice, thereby validating a model hypothesis to account for winter time SSA maxima in polar regions not explained otherwise. Blowing or drifting snow always lead to increases in SSA during and after storms. Observed aerosol gradients suggest that net production of SSA takes place near the top of the blowing or drifting snow layer. The observed relative increase of SSA concentrations with wind speed suggests that on average the corresponding aerosol mass flux during storms was equal or larger above sea ice than above the open ocean, demonstrating the importance of the blowing snow source for SSA in winter and early spring. For the first time it is shown that snow on sea ice is depleted in sulphate relative to sodium with respect to sea water. Similar depletion observed in the aerosol suggests that most sea salt originated from snow on sea ice and not the open ocean or leads, e.g. on average 93 % during the 8 June and 12 August 2013 period. A mass budget calculation shows that sublimation of snow even with low salinity (

Formation of the Three-Layered Structure of the Amery Ice Shelf, Antarctica

Journal of Glaciology ◽

10.3189/s002214300003166x ◽

1976 ◽

Vol 16 (74) ◽

pp. 295-296 ◽

Cited By ~ 1

Author(s):

Gorow Wakahama ◽

W.F. Budd

Keyword(s):

Layered Structure ◽

Sea Water ◽

Ice Cores ◽

Middle Layer ◽

Bottom Layer ◽

Bottom Surface ◽

Ice Shelf ◽

Amery Ice Shelf ◽

Glacier Ice ◽

Cooperative Project

AbstractExtensive glaciological studies on the Amery Ice Shell have been conducted since 1962 by the Australian National Antarctic Research Expeditions (ANARE). Deep core drilling to the depth of 310 m was carried out in 1968 at the site GI on the shell in order to obtain the vertical ice temperature distribution and to collect ice cores over the whole depth of the bore hole. General core analyses have been conducted since 1970 under an Australia- Japan Cooperative Project in order to clarify the structure of the ice shelf in connection with its flow.It was found through these analyses that the Amery Ice Shelf consists of three layers of different origin, which are denoted the top, middle, and bottom layers. The top layer is formed by the in situ accumulation of snow on the shelf, the middle layer is glacier ice flowing from the Lambert Glacier, originating far inland on the Antarctic ice sheet, and the bottom layer is developed by the freezing of sea-water at the bottom surface. Numerical calculations were made of the formation processes of the three-layered structure of the ice shelf, in which the accumulation and the densification of snow at the top surface, the straining of the shelf, and the freezing of sea-water at the bottom surface were taken into account.The thicknesses of the top and the bottom layers at site G1 obtained from the present calculations agree well with (hose obtained from the core analyses. The freezing rate of seawater at the bottom surface of the ice shelf estimated from the temperature profile is approximately 0.5 m a-1. This considerable growth of frozen sea-water at the base of the ice shelf results in water flowing out from under the ice shelf being more saline and warmer than that flowing in.

Past ice sheet-seabed interactions in the northeastern Weddell Sea Embayment, Antarctica

10.5194/tc-2019-271 ◽

2019 ◽

Author(s):

Jan Erik Arndt ◽

Robert D. Larter ◽

Claus-Dieter Hillenbrand ◽

Simon H. Sørli ◽

Matthias Forwick ◽

...

Keyword(s):

Ice Sheet ◽

Weddell Sea ◽

Ice Shelf ◽

Antarctic Ice Sheet ◽

Seafloor Morphology ◽

Ice Stream ◽

Time Period ◽

Single Location ◽

The Antarctic ◽

Near Future

Abstract. The Antarctic Ice Sheet extent in the Weddell Sea Embayment (WSE) during the Last Glacial Maximum (LGM; ca. 19–25 calibrated kiloyears before present, cal. ka BP) and its subsequent retreat from the shelf are poorly constrained, with two conflicting scenarios being discussed. Today, the modern Brunt Ice Shelf, the last remaining ice shelf in the northeastern WSE, is only pinned at a single location and recent crevasse development may lead to its rapid disintegration in the near future. We investigated the seafloor morphology on the northeastern WSE shelf and discuss its implications, in combination with marine geological records, for reconstructions of the past behaviour of this sector of the East Antarctic Ice Sheet (EAIS), including ice-seafloor interactions. Our data show that an ice stream flowed through Stancomb-Wills Trough and acted as the main conduit for EAIS drainage during the LGM. Post-LGM ice-stream retreat occurred stepwise, with at least three documented grounding line still stands, and the trough had become free of grounded ice by ~10.5 cal. ka BP. In contrast, slow-flowing ice once covered the shelf in Brunt Basin and extended westwards toward McDonald Bank. During a later time period, only floating ice was present within Brunt Basin, but large ‘ice slabs’ enclosed within the ice shelf occasionally ran aground at the eastern side of McDonald Bank, forming ten unusual ramp-shaped seabed features. These ramps are the result of temporary ice-shelf grounding events buttressing the ice further upstream. To the west of this area, Halley Trough very likely was free of grounded ice during the LGM, representing a potential refuge for benthic shelf fauna at this time.

Water Circulation and Ice Accretion Beneath Ward Hunt Ice Shelf (Northern Ellesmere Island, Canada), Deduced From Salinity and Isotope Analysis of Ice Cores

Annals of Glaciology ◽

10.3189/s0260305500004195 ◽

1988 ◽

Vol 10 ◽

pp. 68-72 ◽

Cited By ~ 3

Author(s):

Martin O. Jeffries ◽

William M. Sackinger ◽

H. Roy Krouse ◽

Harold V. Serson

Keyword(s):

Sea Ice ◽

Fresh Water ◽

Sea Water ◽

Ice Core ◽

Isotope Analysis ◽

Ice Cores ◽

Water Circulation ◽

Ice Shelf ◽

The West ◽

Water Ice

Ice-core drilling and ice-core analysis (electrical conductivity–salinity, 18O, 3H, density) reveal that the internal structure of the west Ward Hunt Ice Shelf contrasts sharply with that of the east ice shelf. The west ice shelf contains a great thickness (≥22 m) of sea ice (mean salinity, 2.22‰; mean δ18O, -0.8‰), whereas the east ice shelf is entirely of meteoric or fresh-water ice (mean salinity 0.01‰; mean δ18O, -29.7‰). High tritium activities are found only in ice from near the bottom of the east and west ice shelves. The contrasting ice-core data is considered to be a proxy record of variations in water circulation and bottom freezing beneath the ice shelf. The west shelf is underlain by sea water flowing into Disraeli Fiord. Sea ice accretes on to the bottom of the west ice shelf from the sea-water flowing into the fiord. Sea-water flowing out of the fiord is directed below the east ice shelf. However, the east ice shelf is not underlain directly by sea-water but by a layer of fresh water from the surface of Disraeli Fiord. In this region, ice growth resulting from the presence of this stable fresh-water layer has been accompanied by surface ablation over a period of perhaps the last 450 years. As a result, fresh-water ice has completely replaced any sea ice that originally grew in the region of the east ice shelf. Whereas the west and east shelves are underlain almost exclusively by sea-water and fresh water, ice in the south shelf is the result of freezing of fresh, brackish or sea water. This is attributed to mixing of the inflowing and outflowing waters.

Past ice sheet–seabed interactions in the northeastern Weddell Sea embayment, Antarctica

The Cryosphere ◽

10.5194/tc-14-2115-2020 ◽

2020 ◽

Vol 14 (6) ◽

pp. 2115-2135

Author(s):

Jan Erik Arndt ◽

Robert D. Larter ◽

Claus-Dieter Hillenbrand ◽

Simon H. Sørli ◽

Matthias Forwick ◽

...

Keyword(s):

Ice Sheet ◽

Weddell Sea ◽

Ice Shelf ◽

Antarctic Ice Sheet ◽

Seafloor Morphology ◽

Ice Stream ◽

Time Period ◽

Single Location ◽

The Antarctic ◽

Near Future

Abstract. The Antarctic ice sheet extent in the Weddell Sea embayment (WSE) during the Last Glacial Maximum (LGM; ca. 19–25 calibrated kiloyears before present, ka cal BP) and its subsequent retreat from the shelf are poorly constrained, with two conflicting scenarios being discussed. Today, the modern Brunt Ice Shelf, the last remaining ice shelf in the northeastern WSE, is only pinned at a single location and recent crevasse development may lead to its rapid disintegration in the near future. We investigated the seafloor morphology on the northeastern WSE shelf and discuss its implications, in combination with marine geological records, to create reconstructions of the past behaviour of this sector of the East Antarctic Ice Sheet (EAIS), including ice–seafloor interactions. Our data show that an ice stream flowed through Stancomb-Wills Trough and acted as the main conduit for EAIS drainage during the LGM in this sector. Post-LGM ice stream retreat occurred stepwise, with at least three documented grounding-line still-stands, and the trough had become free of grounded ice by ∼10.5 ka cal BP. In contrast, slow-flowing ice once covered the shelf in Brunt Basin and extended westwards toward McDonald Bank. During a later time period, only floating ice was present within Brunt Basin, but large “ice slabs” enclosed within the ice shelf occasionally ran aground at the eastern side of McDonald Bank, forming 10 unusual ramp-shaped seabed features. These ramps are the result of temporary ice shelf grounding events buttressing the ice further upstream. To the west of this area, Halley Trough very likely was free of grounded ice during the LGM, representing a potential refuge for benthic shelf fauna at this time.

Variability of sea salts in ice and firn cores from Fimbul Ice Shelf, Dronning Maud Land, Antarctica

The Cryosphere ◽

10.5194/tc-12-1681-2018 ◽

2018 ◽

Vol 12 (5) ◽

pp. 1681-1697 ◽

Cited By ~ 4

Author(s):

Carmen Paulina Vega ◽

Elisabeth Isaksson ◽

Elisabeth Schlosser ◽

Dmitry Divine ◽

Tõnu Martma ◽

...

Keyword(s):

Sea Ice ◽

Major Ions ◽

Ice Cores ◽

Precipitation Chemistry ◽

Sea Salt ◽

Ice Shelf ◽

Study Region ◽

Sea Salt Aerosol ◽

Antarctic Sea Ice ◽

Dronning Maud Land

Abstract. Major ions were analysed in firn and ice cores located at Fimbul Ice Shelf (FIS), Dronning Maud Land – DML, Antarctica. FIS is the largest ice shelf in the Haakon VII Sea, with an extent of approximately 36 500 km2. Three shallow firn cores (about 20 m deep) were retrieved in different ice rises, Kupol Ciolkovskogo (KC), Kupol Moskovskij (KM), and Blåskimen Island (BI), while a 100 m long core (S100) was drilled near the FIS edge. These sites are distributed over the entire FIS area so that they provide a variety of elevation (50–400 m a.s.l.) and distance (3–42 km) to the sea. Sea-salt species (mainly Na+ and Cl−) generally dominate the precipitation chemistry in the study region. We associate a significant sixfold increase in median sea-salt concentrations, observed in the S100 core after the 1950s, to an enhanced exposure of the S100 site to primary sea-salt aerosol due to a shorter distance from the S100 site to the ice front, and to enhanced sea-salt aerosol production from blowing salty snow over sea ice, most likely related to the calving of Trolltunga occurred during the 1960s. This increase in sea-salt concentrations is synchronous with a shift in non-sea-salt sulfate (nssSO42−) toward negative values, suggesting a possible contribution of fractionated aerosol to the sea-salt load in the S100 core most likely originating from salty snow found on sea ice. In contrast, there is no evidence of a significant contribution of fractionated sea salt to the ice-rises sites, where the signal would be most likely masked by the large inputs of biogenic sulfate estimated for these sites. In summary, these results suggest that the S100 core contains a sea-salt record dominated by the proximity of the site to the ocean, and processes of sea ice formation in the neighbouring waters. In contrast, the ice-rises firn cores register a larger-scale signal of atmospheric flow conditions and a less efficient transport of sea-salt aerosols to these sites. These findings are a contribution to the understanding of the mechanisms behind sea-salt aerosol production, transport and deposition at coastal Antarctic sites, and the improvement of the current Antarctic sea ice reconstructions based on sea-salt chemical proxies obtained from ice cores.