scholarly journals Zonation in a cryptic Antarctic intertidal macrofaunal community

2012 ◽  
Vol 25 (1) ◽  
pp. 62-68 ◽  
Author(s):  
Catherine L. Waller
Keyword(s):  
Outer Surface ◽  
Intertidal Zone ◽  
General View ◽  
Annual Cycles ◽  
West Antarctic ◽  
Order Of Magnitude ◽  
Size Of Animals ◽  
Study Sites ◽  
Macrofaunal Community ◽  
The Antarctic

AbstractDespite the general view that the Antarctic intertidal conditions are too extreme to support obvious signs of macrofaunal life, recent studies have shown that intertidal communities can survive over annual cycles. The current study investigates distribution of taxa within a boulder cobble matrix, beneath the outer, scoured surface of the intertidal zone at Adelaide Island, west Antarctic Peninsula. The intertidal zone at the study sites comprised compacted, flattened cobble pavements, which have been shown to be highly stable over time. Community structure was investigated using univariate and multivariate approaches. Virtually no macrofauna were present on the outer surface, but richness, diversity, abundance and size of animals increased with depth into the rock matrix. Abundance of taxa increased by an order of magnitude between the outer surface and the lowest level sampled. These findings show that the Antarctic intertidal is not always the uninhabitable environment currently perceived, and that under these highly variable environmental conditions at least some species have the capacity to survive.

scholarly journals Relating Hydrodynamic Forcing and Topographic Response for Tide-Dominated Sandy Beaches

2020 ◽  
Vol 8 (3) ◽  
pp. 151 ◽  
Author(s):  
Evelien Brand ◽  
Anne-Lise Montreuil ◽  
Rik Houthuys ◽  
Margaret Chen
Keyword(s):  
Intertidal Zone ◽  
Spring Tide ◽  
Field Measurements ◽  
Sandy Beaches ◽  
Tidal Currents ◽  
Sediment Supply ◽  
Wave Steepness ◽  
Natural Sediment ◽  
Order Of Magnitude ◽  
Study Sites

To relate hydrodynamic forcing and topographic response for a tide-dominated sandy beach, extensive field measurements were carried out in the intertidal zone. Hydrodynamics and beach topography were monitored during a total of 12 weeks at two different study sites: one with a featureless intertidal zone and one with intertidal bars. The results of both study sites indicate that the intertidal beach grows when wave steepness is small, whereas it erodes when wave steepness is large. Spring-neap variations in tidal current direction heavily distort this trend: strong spring tidal currents transport sediment away from the beach, resulting in enhanced erosion. Tide-induced beach volume changes are on the same order of magnitude as wave-induced changes. Besides waves and tides, the effect of variations in the amount of sediment supply is substantial, with enhanced accretion when the sediment supply is large. The effect of variations in sediment supply on the intertidal beach topography is subordinate to the effect of waves and tide, though. From this study, it is concluded that larger waves are primarily erosive, but they can also enhance the natural sediment supply. Furthermore, it is found that tidal currents can be equally important as waves in shaping the beach topography, especially during spring tide on macrotidal beaches.

scholarly journals Glacial melt disturbance shifts community metabolism of an Antarctic seafloor ecosystem from net autotrophy to heterotrophy

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Ulrike Braeckman ◽  
Francesca Pasotti ◽  
Ralf Hoffmann ◽  
Susana Vázquez ◽  
Angela Wulff ◽  
...  
Keyword(s):  
Carbon Balance ◽  
Benthic Communities ◽  
Benthic Primary Production ◽  
Community Metabolism ◽  
West Antarctic ◽  
Run Off ◽  
Net Heterotrophy ◽  
Benthic Ecosystems ◽  
The Antarctic

AbstractClimate change-induced glacial melt affects benthic ecosystems along the West Antarctic Peninsula, but current understanding of the effects on benthic primary production and respiration is limited. Here we demonstrate with a series of in situ community metabolism measurements that climate-related glacial melt disturbance shifts benthic communities from net autotrophy to heterotrophy. With little glacial melt disturbance (during cold El Niño spring 2015), clear waters enabled high benthic microalgal production, resulting in net autotrophic benthic communities. In contrast, water column turbidity caused by increased glacial melt run-off (summer 2015 and warm La Niña spring 2016) limited benthic microalgal production and turned the benthic communities net heterotrophic. Ongoing accelerations in glacial melt and run-off may steer shallow Antarctic seafloor ecosystems towards net heterotrophy, altering the metabolic balance of benthic communities and potentially impacting the carbon balance and food webs at the Antarctic seafloor.

scholarly journals Antarctic Ice-Sheet Volume at 18000 Years B.P. and Holocene Sea-Level Changes at the West Antarctic Margin

1979 ◽  
Vol 24 (90) ◽  
pp. 213-230 ◽  
Author(s):  
Craig S. Lingle ◽  
James A. Clark
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Ice Sheet ◽  
Sea Level Changes ◽  
Ice Shelf ◽  
Relative Sea Level ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
The Antarctic

AbstractThe Antarctic ice sheet has been reconstructed at 18000 years b.p. by Hughes and others (in press) using an ice-flow model. The volume of the portion of this reconstruction which contributed to a rise of post-glacial eustatic sea-level has been calculated and found to be (9.8±1.5) × 106 km3. This volume is equivalent to 25±4 m of eustatic sea-level rise, defined as the volume of water added to the ocean divided by ocean area. The total volume of the reconstructed Antarctic ice sheet was found to be (37±6) × 106 km3. If the results of Hughes and others are correct, Antarctica was the second largest contributor to post-glacial eustatic sea-level rise after the Laurentide ice sheet. The Farrell and Clark (1976) model for computation of the relative sea-level changes caused by changes in ice and water loading on a visco-elastic Earth has been applied to the ice-sheet reconstruction, and the results have been combined with the changes in relative sea-level caused by Northern Hemisphere deglaciation as previously calculated by Clark and others (1978). Three families of curves have been compiled, showing calculated relative sea-level change at different times near the margin of the possibly unstable West Antarctic ice sheet in the Ross Sea, Pine Island Bay, and the Weddell Sea. The curves suggest that the West Antarctic ice sheet remained grounded to the edge of the continental shelf until c. 13000 years b.p., when the rate of sea-level rise due to northern ice disintegration became sufficient to dominate emergence near the margin predicted otherwise to have been caused by shrinkage of the Antarctic ice mass. In addition, the curves suggest that falling relative sea-levels played a significant role in slowing and, perhaps, reversing retreat when grounding lines approached their present positions in the Ross and Weddell Seas. A predicted fall of relative sea-level beneath the central Ross Ice Shelf of as much as 23 m during the past 2000 years is found to be compatible with recent field evidence that the ice shelf is thickening in the south-east quadrant.

scholarly journals Preliminary Study on Fish Larvae at Selected Coastal Waters of Sarawak

1970 ◽  
Vol 4 (2) ◽  
pp. 1-8
Author(s):  
Norhakimi Muhamad ◽  
Siti Akmar Khadijah Ab Rahim
Keyword(s):  
Coastal Waters ◽  
Intertidal Zone ◽  
Larval Dispersal ◽  
Sampling Methods ◽  
Fish Larvae ◽  
Mesh Size ◽  
Subtidal Zone ◽  
Preliminary Study ◽  
Study Sites

A survey were carried out from April to November 2012 at five study sites namely Teluk Pandan beach, Rambungan beach, Puteri beach, Sampadi Island and Satang Besar Island, Sarawak. This survey was carried out in order to obtain early documentation of fish larvae at selected coastal waters of Sarawak. Seine net (1 mm mesh size) which was pulled by two persons at intertidal zone; and bridle net (0.5 mm mesh size) that was towed by boat at subtidal zone (Sampadi Island only) were used to collect the samples. A total of 2,562 fish larvae which comprise 25 families were obtained from both sampling methods. A total of 16 families of fish larvae were caught by seine net from the intertidal zone. The same number of families was collected at the subtidal zone of Sampadi Island by bridle net. Ambassidae, Clupeidae, Engraulidae and Gerreidae found to be dominant families in the study sites. Clupeidae and Gerreidae shown a wide larval dispersal area because they were collected at all study sites. These findings seem to indicate that the subtidal zone of Sampadi support more species of fish larvae.

scholarly journals Simultaneous solution for mass trends on the West Antarctic Ice Sheet

2014 ◽  
Vol 8 (3) ◽  
pp. 2995-3035 ◽  
Author(s):  
N. Schön ◽  
A. Zammit-Mangion ◽  
J. L. Bamber ◽  
J. Rougier ◽  
T. Flament ◽  
...  
Keyword(s):  
Mass Loss ◽  
Antarctic Peninsula ◽  
Ice Sheet ◽  
The West ◽  
Spatial Error ◽  
Antarctic Ice Sheet ◽  
Forward Models ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
The Antarctic

Abstract. The Antarctic Ice Sheet is the largest potential source of future sea-level rise. Mass loss has been increasing over the last two decades in the West Antarctic Ice Sheet (WAIS), but with significant discrepancies between estimates, especially for the Antarctic Peninsula. Most of these estimates utilise geophysical models to explicitly correct the observations for (unobserved) processes. Systematic errors in these models introduce biases in the results which are difficult to quantify. In this study, we provide a statistically rigorous, error-bounded trend estimate of ice mass loss over the WAIS from 2003–2009 which is almost entirely data-driven. Using altimetry, gravimetry, and GPS data in a hierarchical Bayesian framework, we derive spatial fields for ice mass change, surface mass balance, and glacial isostatic adjustment (GIA) without relying explicitly on forward models. The approach we use separates mass and height change contributions from different processes, reproducing spatial features found in, for example, regional climate and GIA forward models, and provides an independent estimate, which can be used to validate and test the models. In addition, full spatial error estimates are derived for each field. The mass loss estimates we obtain are smaller than some recent results, with a time-averaged mean rate of −76 ± 15 GT yr−1 for the WAIS and Antarctic Peninsula (AP), including the major Antarctic Islands. The GIA estimate compares very well with results obtained from recent forward models (IJ05-R2) and inversion methods (AGE-1). Due to its computational efficiency, the method is sufficiently scalable to include the whole of Antarctica, can be adapted for other ice sheets and can easily be adapted to assimilate data from other sources such as ice cores, accumulation radar data and other measurements that contain information about any of the processes that are solved for.

scholarly journals Refinement of the ice absorption spectrum in the visible using radiance profile measurements in Antarctic snow

2016 ◽  
Author(s):  
Ghislain Picard ◽  
Quentin Libois ◽  
Laurent Arnaud
Keyword(s):  
Absorption Coefficient ◽  
Fiber Optics ◽  
Estimation Method ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Snow Layer ◽  
Antarctic Snow ◽  
Order Of Magnitude ◽  
The Difference ◽  
The Antarctic

Abstract. Ice is a highly transparent material in the visible. According to the most widely used database (Warren and Brandt, 2008; IA2008), the ice absorption coefficient reaches values lower than 10−3 m−1 around 400 nm. These values were obtained from a radiance profile measured in a single snow layer at Dome C in Antarctica. We reproduced this experiment using a fiber optics inserted in the snow to record 56 profiles from which 70 homogeneous layers were identified. Applying the same estimation method on every layer yields 70 ice absorption spectra with a significant variability and overall larger than IA2008 by one order of magnitude. We devise another estimation method based on Bayesian inference. It reduces the statistical variability and confirms the higher absorption, around 2 × 10−2 m−1 near the minimum at 440 nm. We explore potential instrumental artifacts by developing a 3D radiative transfer model able to explicitly account for the presence of the fiber in the snow. The simulation results show that the radiance profile is indeed perturbed by the fiber intrusion but the error on the ice absorption estimate is not larger than a factor 2. This is insufficient to explain the difference between our new estimate and IA2008. Nevertheless, considering the number of profiles acquired for this study and other estimates from the Antarctic Muon and Neutrino Detector Array (AMANDA), we estimate that ice absorption values around 10−2 m−1 at the minimum are more likely than under 10−3 m−1. We provide a new estimate in the range 400–600 nm for future modeling of snow, cloud, and sea-ice optical properties. Most importantly we recommend that modeling studies take into account the large uncertainty of the ice absorption coefficient in the visible.

scholarly journals Monitoring changes of the Antarctic Ice sheet by GRACE, ICESat and GNSS

2019 ◽  
Vol 49 (4) ◽  
pp. 403-424
Author(s):  
Fang Zou ◽  
Robert Tenzer ◽  
Samurdhika Rathnayake
Keyword(s):  
Mass Loss ◽  
Ice Sheet ◽  
The West ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
Ice Volume ◽  
West Antarctic ◽  
Elevation Changes ◽  
A Minor ◽  
The Antarctic

Abstract In this study, we estimate the ice mass changes, the ice elevation changes and the vertical displacements in Antarctica based on analysis of multi-geodetic datasets that involve the satellite gravimetry (GRACE), the satellite altimetry (ICESat) and the global navigation satellite systems (GNSS). According to our estimates, the total mass change of the Antarctic ice sheet from GRACE data is −162.91 Gt/yr over the investigated period between April 2002 and June 2017. This value was obtained after applying the GIA correction of −98.12 Gt/yr derived from the ICE-5G model of the glacial iso-static adjustment. A more detailed analysis of mass balance changes for three individual drainage regions in Antarctica reveal that the mass loss of the West Antarctic ice sheet was at a rate of −143.11 Gt/yr. The mass loss of the Antarctic Peninsula ice sheet was at a rate of −24.31 Gt/yr. The mass of the East Antarctic ice sheet increased at a rate of 5.29 Gt/yr during the investigated period. When integrated over the entire Antarctic ice sheet, average rates of ice elevation changes over the period from March 2003 to October 2009 derived from ICESat data represent the loss of total ice volume of −155.6 km3.The most prominent features in ice volume changes in Antarctica are characterized by a strong dynamic thinning and ice mass loss in the Amundsen Sea Embayment that is part of the West Antarctic ice sheet. In contrast, coastal regions between Dronning Maud Land and Enderby Land exhibit a minor ice increase, while a minor ice mass loss is observed in Wilkes Land. The vertical load displacement rates estimated from GRACE and GPS data relatively closely agree with the GIA model derived based on the ice-load history and the viscosity profile. For most sites, the GRACE signal appears to be in phase and has the same amplitude as that obtained from the GPS vertical motions while other sites exhibit some substantial differences possibly attributed to thermo-elastic deformations associated with surface temperature.

The role of fish in the Antarctic marine food web: differences between inshore and offshore waters in the southern Scotia Arc and west Antarctic Peninsula

2002 ◽  
Vol 14 (4) ◽  
pp. 293-309 ◽  
Author(s):  
ESTEBAN BARRERA-ORO
Keyword(s):  
Food Web ◽  
Antarctic Peninsula ◽  
Demersal Fish ◽  
Pelagic Fish ◽  
West Antarctic ◽  
Antarctic Marine ◽  
Scotia Arc ◽  
West Antarctic Peninsula ◽  
The Antarctic

The role of fish in the Antarctic food web in inshore and offshore waters is analysed, taking as an example the coastal marine communities of the southern Scotia Arc (South Orkney Islands and South Shetland Islands) and the west Antarctic Peninsula. Inshore, the ecological role of demersal fish is more important than that of krill. There, demersal fish are major consumers of benthos and also feed on zooplankton (mainly krill in summer). They are links between lower and upper levels of the food web and are common prey of other fish, birds and seals. Offshore, demersal fish depend less on benthos and feed more on zooplankton (mainly krill) and nekton, and are less accessible as prey of birds and seals. There, pelagic fish (especially lantern fish) are more abundant than inshore and play an important role in the energy flow from macrozooplankton to higher trophic levels (seabirds and seals). Through the higher fish predators, energy is transferred to land in the form of fish remains, pellets (birds), regurgitation and faeces (birds and seals). However, in the general context of the Antarctic marine ecosystem, krill (Euphausia superba) plays the central role in the food web because it is the main food source in terms of biomass for most of the high level predators from demersal fish up to whales. This has no obvious equivalent in other marine ecosystems. In Antarctic offshore coastal and oceanic waters the greatest proportion of energy from the ecosystem is transferred to land directly through krill consumers, such as flying birds, penguins, and seals. Beside krill, the populations of fish in the Antarctic Ocean are the second most important element for higher predators, in particular the energy-rich pelagic Myctophidae in open waters and the pelagic Antarctic silver fish (Pleuragramma antarcticum) in the high Antarctic zone. Although the occurrence of these pelagic fish inshore has been poorly documented, their abundance in neritic waters could be higher than previously believed.

scholarly journals Microphysics of summer clouds in central West Antarctica simulated by the Polar Weather Research and Forecasting Model (WRF) and the Antarctic Mesoscale Prediction System (AMPS)

2019 ◽  
Vol 19 (19) ◽  
pp. 12431-12454 ◽  
Author(s):  
Keith M. Hines ◽  
David H. Bromwich ◽  
Sheng-Hung Wang ◽  
Israel Silber ◽  
Johannes Verlinde ◽  
...  
Keyword(s):  
Liquid Water ◽  
Radiative Forcing ◽  
Weather Prediction ◽  
The Arctic ◽  
Weather Research And Forecasting ◽  
Forecasting Model ◽  
Prediction System ◽  
West Antarctic ◽  
The Antarctic ◽  
Weather Research

Abstract. The Atmospheric Radiation Measurement (ARM) West Antarctic Radiation Experiment (AWARE) provided a highly detailed set of remote-sensing and surface observations to study Antarctic clouds and surface energy balance, which have received much less attention than for the Arctic due to greater logistical challenges. Limited prior Antarctic cloud observations have slowed the progress of numerical weather prediction in this region. The AWARE observations from the West Antarctic Ice Sheet (WAIS) Divide during December 2015 and January 2016 are used to evaluate the operational forecasts of the Antarctic Mesoscale Prediction System (AMPS) and new simulations with the Polar Weather Research and Forecasting Model (WRF) 3.9.1. The Polar WRF 3.9.1 simulations are conducted with the WRF single-moment 5-class microphysics (WSM5C) used by the AMPS and with newer generation microphysics schemes. The AMPS simulates few liquid clouds during summer at the WAIS Divide, which is inconsistent with observations of frequent low-level liquid clouds. Polar WRF 3.9.1 simulations show that this result is a consequence of WSM5C. More advanced microphysics schemes simulate more cloud liquid water and produce stronger cloud radiative forcing, resulting in downward longwave and shortwave radiation at the surface more in agreement with observations. Similarly, increased cloud fraction is simulated with the more advanced microphysics schemes. All of the simulations, however, produce smaller net cloud fractions than observed. Ice water paths vary less between the simulations than liquid water paths. The colder and drier atmosphere driven by the Global Forecast System (GFS) initial and boundary conditions for AMPS forecasts produces lesser cloud amounts than the Polar WRF 3.9.1 simulations driven by ERA-Interim.

scholarly journals Combustion of available fossil fuel resources sufficient to eliminate the Antarctic Ice Sheet

2015 ◽  
Vol 1 (8) ◽  
pp. e1500589 ◽  
Author(s):  
Ricarda Winkelmann ◽  
Anders Levermann ◽  
Andy Ridgwell ◽  
Ken Caldeira
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Carbon Emissions ◽  
Fossil Fuel ◽  
Ice Sheet ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
Global Sea Level ◽  
The Antarctic

The Antarctic Ice Sheet stores water equivalent to 58 m in global sea-level rise. We show in simulations using the Parallel Ice Sheet Model that burning the currently attainable fossil fuel resources is sufficient to eliminate the ice sheet. With cumulative fossil fuel emissions of 10,000 gigatonnes of carbon (GtC), Antarctica is projected to become almost ice-free with an average contribution to sea-level rise exceeding 3 m per century during the first millennium. Consistent with recent observations and simulations, the West Antarctic Ice Sheet becomes unstable with 600 to 800 GtC of additional carbon emissions. Beyond this additional carbon release, the destabilization of ice basins in both West and East Antarctica results in a threshold increase in global sea level. Unabated carbon emissions thus threaten the Antarctic Ice Sheet in its entirety with associated sea-level rise that far exceeds that of all other possible sources.

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