Intense nutrient removal in the remote area off Larsen Ice Shelf (Weddell Sea)

Polar Biology ◽  
2000 ◽  
Vol 23 (2) ◽  
pp. 85-94 ◽  
Author(s):  
Mario Hoppema ◽  
Leo Goeyens ◽  
Eberhard Fahrbach
Keyword(s):  
Nutrient Removal ◽  
Remote Area ◽  
Weddell Sea ◽  
Ice Shelf ◽  
Larsen Ice Shelf

scholarly journals Spatiotemporal variations in the surface velocities of Antarctic Peninsula glaciers

2014 ◽  
Vol 8 (6) ◽  
pp. 5875-5910
Author(s):  
J. Chen ◽  
C. Q. Ke ◽  
Z. D. Shao
Keyword(s):  
Antarctic Peninsula ◽  
Spatial Scales ◽  
Weddell Sea ◽  
Glacier Mass Balance ◽  
Spatiotemporal Variations ◽  
Ice Shelf ◽  
Macro Scale ◽  
Velocity Variations ◽  
Glacier Velocity ◽  
Larsen Ice Shelf

Abstract. Velocity is an important parameter for the estimation of glacier mass balance, which directly signals the response of glaciers to climate change. Antarctic ice sheet movement and the associated spatiotemporal velocity variations are of great significance to global sea level rise. In this study, we estimate Antarctic Peninsula glacier velocities using the co-registration of optically sensed images and correlation (hereafter referred to as COSI-Corr) based on moderate-resolution imaging spectroradiometer Level 1B data (hereafter referred to as MODIS L1B). The results show that the glaciers of Graham Land and the Larsen Ice Shelf have substantially different velocity features. The Graham Land glaciers primarily flow from the peninsula ridge towards the Weddell Sea and Bellingshausen Sea on the east and west sides, respectively. There are very large velocity variations among the different ice streams, with a minimum of < 20 m a−1 and a maximum of 1500 m a−1 (with an average of 100–150 m a−1). Over the period 2000–2012, the glaciers of Graham Land accelerated in the south but slowed down in the north. In contrast, the Larsen Ice Shelf flows in a relatively uniform direction, mainly towards the northeast into the Weddell Sea. Its average velocity is 750–800 m a−1 and the maximum is > 1500 m a−1. During the period 2000–2012, the Larsen Ice Shelf experienced significant acceleration. The use of COSI-Corr based on MODIS L1B data is suitable for glacier velocity monitoring on the Antarctic Peninsula over long time series and large spatial scales. This method is clearly advantageous for analysing macro-scale spatiotemporal variations in glacier movement.

scholarly journals Clay Mineralogical Characteristics of Sediments Deposited during the Late Quaternary in the Larsen Ice Shelf B Embayment, Antarctica

Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 153 ◽  
Author(s):  
Jaewoo Jung ◽  
Kyu-Cheul Yoo ◽  
Kee-Hwan Lee ◽  
Young Park ◽  
Jae Lee ◽  
...  
Keyword(s):  
Mineral Composition ◽  
Clay Mineral ◽  
Late Quaternary ◽  
Sedimentary Facies ◽  
Weddell Sea ◽  
Silty Clay ◽  
Ice Shelf ◽  
Δ13c And Δ15n ◽  
Larsen Ice Shelf ◽  
Clay Mineral Composition

Variations in grain size, clay mineral composition, and stable isotopes (δ13C and δ15N) are closely linked to the sedimentary facies that reflect mineralogical and geochemical modification during the retreat and advance of the Larsen ice shelf. A whole round core of marine sediment (EAP13-GC17, 236 cm below the sea floor) was collected on the northwestern Larsen B embayment of the Antarctic Peninsula during a marine geological expedition (the ARA13 Cruise Expedition by the Korea Polar Research Institute, 2013). Four sedimentary facies (U1–U4) were clearly distinguishable: bioturbated sandy mud (open marine, U1), laminated sandy mud (sub–floating ice shelf, U2), sandy clay aggregates (deglacial, U3), and muddy diamictons (sub-glacial, U4), as well as interbedded silty. Clay minerals, including smectite, chlorite, illite, and kaolinite, were detected throughout the core. An increase in the clay mineral ratio of smectite/(illite + chlorite) was clearly observed in the open marine condition, which was strongly indicated by both a heavier isotopic composition of δ13C and δ15N (−24.4‰ and 4.3‰, respectively), and an abrupt increase in 10Be concentration (~30 times). An increase in the average values of the crystal packet thickness of illite (~1.5 times) in U1 also indicated sediments transported in open marine conditions. Based on the clay mineral composition in U1, the sediments are likely to have been transported from the Weddell Sea. The clay mineralogical assessments conducted in this region have significant implications for our understanding of paleodepositional environments.

Dinoflagellates in a fast-ice covered inlet of the Riiser-Larsen Ice Shelf (Weddell Sea)

Polar Biology ◽  
2009 ◽  
Vol 32 (9) ◽  
pp. 1331-1343 ◽  
Author(s):  
Anna Jadwiga Pieńkowski ◽  
Fabienne Marret ◽  
David N. Thomas ◽  
James D. Scourse ◽  
Gerhard S. Dieckmann
Keyword(s):  
Weddell Sea ◽  
Ice Shelf ◽  
Fast Ice ◽  
Larsen Ice Shelf

Attenuated carbon sequestration by Weddell Sea dense waters over the 21st century – an assessment with FESOM-REcoM

2021 ◽  
Author(s):  
Cara Nissen ◽  
Ralph Timmermann ◽  
Mario Hoppema ◽  
Judith Hauck
Keyword(s):  
Carbon Sequestration ◽  
Sea Ice ◽  
Continental Shelf ◽  
Bottom Water ◽  
Water Mass ◽  
Weddell Sea ◽  
Ice Shelf ◽  
Deep Waters ◽  
Water Formation ◽  
Water Mass Transformation

&lt;p&gt;Deep and bottom water formation regions have long been recognized to be efficient vectors for carbon transfer to depth, leading to carbon sequestration on time scales of centuries or more. Precursors of Antarctic Bottom Water (AABW) are formed on the Weddell Sea continental shelf as a consequence of buoyancy loss of surface waters at the ice-ocean or atmosphere-ocean interface, which suggests that any change in water mass transformation rates in this area affects global carbon cycling and hence climate. Many of the models previously used to assess AABW formation in present and future climates contained only crude representations of ocean-ice shelf interaction. Numerical simulations often featured spurious deep convection in the open ocean, and changes in carbon sequestration have not yet been assessed at all. Here, we present results from the global model FESOM-REcoM, which was run on a mesh with elevated grid resolution in the Weddell Sea and which includes an explicit representation of sea ice and ice shelves. Forcing this model with ssp585 scenario output from the AWI Climate Model, we assess changes over the 21&lt;sup&gt;st&lt;/sup&gt; century in the formation and northward export of dense waters and the associated carbon fluxes within and out of the Weddell Sea. We find that the northward transport of dense deep waters (&amp;#963;&lt;sub&gt;2&lt;/sub&gt;&gt;37.2 kg m&lt;sup&gt;-3&lt;/sup&gt; below 2000 m) across the SR4 transect, which connects the tip of the Antarctic Peninsula with the eastern Weddell Sea, declines from 4 Sv to 2.9 Sv by the year 2100. Concurrently, despite the simulated continuous increase in surface ocean CO&lt;sub&gt;2&lt;/sub&gt; uptake in the Weddell Sea over the 21&lt;sup&gt;st&lt;/sup&gt; century, the carbon transported northward with dense deep waters declines from 3.5 Pg C yr&lt;sup&gt;-1&lt;/sup&gt; to 2.5 Pg C yr&lt;sup&gt;-1&lt;/sup&gt;, demonstrating the dominant role of dense water formation rates for carbon sequestration. Using the water mass transformation framework, we find that south of SR4, the formation of downwelling dense waters declines from 3.5 Sv in the 1990s to 1.6 Sv in the 2090s, a direct result of the 18% lower sea-ice formation in the area, the increased presence of modified Warm Deep Water on the continental shelf, and 50% higher ice shelf basal melt rates. Given that the reduced formation of downwelling water masses additionally occurs at lighter densities in FESOM-REcoM in the 2090s, this will directly impact the depth at which any additional oceanic carbon uptake is stored, with consequences for long-term carbon sequestration.&lt;/p&gt;

Estimating Surface Melt on the Larsen Ice Shelf Using a Deep Neural Network: Opportunities and Challenges

2021 ◽  
Author(s):  
Zhongyang Hu ◽  
Peter Kuipers Munneke ◽  
Stef Lhermitte ◽  
Maaike Izeboud ◽  
Michiel van den Broeke
Keyword(s):  
Neural Network ◽  
Remote Sensing ◽  
Deep Neural Network ◽  
Climate Model ◽  
Climate Modeling ◽  
Coefficient Of Determination ◽  
Ice Shelf ◽  
Heterogeneous Terrain ◽  
Surface Melt ◽  
Larsen Ice Shelf

&lt;p&gt;Presently, surface melt over Antarctica is estimated using climate modeling or remote sensing. However, accurately estimating surface melt remains challenging. Both climate modeling and remote sensing have limitations, particularly in the most crucial areas with intense surface melt.&amp;#160; The motivation of our study is to investigate the opportunities and challenges in improving the accuracy of surface melt estimation using a deep neural network. The trained deep neural network uses meteorological observations from automatic weather stations (AWS) and surface albedo observations from satellite imagery to improve surface melt simulations from the regional atmospheric climate model version 2.3p2 (RACMO2). Based on observations from three AWS at the Larsen B and C Ice Shelves, cross-validation shows a high accuracy (root mean square error = 0.898 mm.w.e.d&lt;sup&gt;&amp;#8722;1&lt;/sup&gt;, mean absolute error = 0.429 mm.w.e.d&lt;sup&gt;&amp;#8722;1&lt;/sup&gt;, and coefficient of determination = 0.958). The deep neural network also outperforms conventional machine learning models (e.g., random forest regression, XGBoost) and a shallow neural network. To compute surface melt for the entire Larsen Ice Shelf, the deep neural network is applied to RACMO2 simulations. The resulting, corrected surface melt shows a better correlation with the AWS observations in AWS 14 and 17, but not in AWS 18. Also, the spatial pattern of the surface melt is improved compared to the original RACMO2 simulation. A possible explanation for the mismatch at AWS 18 is its complex geophysical setting. Even though our study shows an opportunity to improve surface melt simulations using a deep neural network, further study is needed to refine the method, especially for complicated, heterogeneous terrain.&lt;/p&gt;

Mesoscale, tidal and seasonal/interannual drivers of the Weddell Sea overturning circulation

2021 ◽  
Keyword(s):  
Continental Shelf ◽  
Shelf Break ◽  
Weddell Sea ◽  
Global Ocean ◽  
Mean Flow ◽  
Ice Shelf ◽  
Overturning Circulation ◽  
Global Circulation ◽  
Interannual Fluctuations ◽  
Continental Shelf Break

Abstract The Weddell Sea supplies 40–50% of the Antarctic BottomWaters that fill the global ocean abyss, and therefore exerts significant influence over global circulation and climate. Previous studies have identified a range of different processes that may contribute to dense shelf water (DSW) formation and export on the southern Weddell Sea continental shelf. However, the relative importance of these processes has not been quantified, which hampers prioritization of observational deployments and development of model parameterizations in this region. In this study a high-resolution (1/12°) regional model of the southern Weddell Sea is used to quantify the overturning circulation and decompose it into contributions due to multi-annual mean flows, seasonal/interannual variability, tides, and other sub-monthly variability. It is shown that tides primarily influence the overturning by changing the melt rate of the Filchner-Ronne Ice Shelf (FRIS). The resulting ~0.2 Sv decrease in DSW transport is comparable to the magnitude of the overturning in the FRIS cavity, but small compared to DSW export across the continental shelf break. Seasonal/interannual fluctuations exert a modest influence on the overturning circulation due to the relatively short (8-year) analysis period. Analysis of the transient energy budget indicates that the non-tidal, sub-monthly variability is primarily baroclinically-generated eddies associated with dense overflows. These eddies play a comparable role to the mean flow in exporting dense shelf waters across the continental shelf break, and account for 100% of the transfer of heat onto the continental shelf. The eddy component of the overturning is sensitive to model resolution, decreasing by a factor of ~2 as the horizontal grid spacing is refined from 1/3° to 1/12°.

scholarly journals Ice-Ocean Interaction On Ronne Ice Shelf, Antarctica

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.

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