scholarly journals Development of AUV MONACA - Hover-Capable Platform for Detailed Observation Under Ice –

2021 ◽  
Vol 33 (6) ◽  
pp. 1223-1233
Author(s):  
Hirokazu Yamagata ◽  
Shuma Kochii ◽  
Hiroshi Yoshida ◽  
Yoshifumi Nogi ◽  
Toshihiro Maki ◽  
...  
Keyword(s):  
Sea Ice ◽  
Autonomous Navigation ◽  
Global Climate ◽  
Autonomous Underwater Vehicles ◽  
Ocean Currents ◽  
Three Dimensions ◽  
Antarctic Ocean ◽  
Ice Shelves ◽  
Sea Trial ◽  
The Antarctic

The melting of ice and changes in ocean currents in Antarctica must be investigated to understand global climate change. In this regard, the volume changes of sea ice and ice shelves, bathymetry, and ocean currents in the Antarctic Ocean must be measured in three dimensions. Therefore, the use of autonomous underwater vehicles (AUVs), which can directly observe under ice, is being considered. The authors developed an AUV named Mobility Oriented Nadir AntarctiC Adventurer (MONACA) to observe sea ice and the lower region of the ice shelf in the Antarctic Ocean. Herein, we describe MONACA and its basic autonomous navigation methods (altitude control, depth control, and waypoint tracking), as well as report the results of a sea experiment conducted in Shimoda Bay, Japan. During the 5-day sea trial, the MONACA successfully measured bathymetry by tracking 15 waypoints in sequence, switching the control criteria in the -axis direction between 3 m depth and 3 m altitude.

Cryosphere

2004 ◽  
Author(s):  
Kenneth M. Hinkel ◽  
Andrew W. Ellis
Keyword(s):  
Sea Ice ◽  
Snow Cover ◽  
Global Climate ◽  
Ice Sheets ◽  
Past Century ◽  
High Latitudes ◽  
Ice Shelves ◽  
The Past ◽  
Third Assessment Report ◽  
The Antarctic

The cryosphere refers to the Earth’s frozen realm. As such, it includes the 10 percent of the terrestrial surface covered by ice sheets and glaciers, an additional 14 percent characterized by permafrost and/or periglacial processes, and those regions affected by ephemeral and permanent snow cover and sea ice. Although glaciers and permafrost are confined to high latitudes or altitudes, areas seasonally affected by snow cover and sea ice occupy a large portion of Earth’s surface area and have strong spatiotemporal characteristics. Considerable scientific attention has focused on the cryosphere in the past decade. Results from 2 ×CO2 General Circulation Models (GCMs) consistently predict enhanced warming at high latitudes, especially over land (Fitzharris 1996). Since a large volume of ground and surface ice is currently within several degrees of its melting temperature, the cryospheric system is particularly vulnerable to the effects of regional warming. The Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) states that there is strong evidence of Arctic air temperature warming over land by as much as 5 °C during the past century (Anisimov et al. 2001). Further, sea-ice extent and thickness has recently decreased, permafrost has generally warmed, spring snow extent over Eurasia has been reduced, and there has been a general warming trend in the Antarctic (e.g. Serreze et al. 2000). Most climate models project a sustained warming and increase in precipitation in these regions over the twenty-first century. Projected impacts include melting of ice sheets and glaciers with consequent increase in sea level, possible collapse of the Antarctic ice shelves, substantial loss of Arctic Ocean sea ice, and thawing of permafrost terrain. Such rapid responses would likely have a substantial impact on marine and terrestrial biota, with attendant disruption of indigenous human communities and infrastructure. Further, such changes can trigger positive feedback effects that influence global climate. For example, melting of organic-rich permafrost and widespread decomposition of peatlands might enhance CO2 and CH4 efflux to the atmosphere. Cryospheric researchers are therefore involved in monitoring and documenting changes in an effort to separate the natural variability from that induced or enhanced by human activity.

Remote sensing of multiyear ice in the Antarctic

2021 ◽  
Author(s):  
Christian Melsheimer ◽  
Gunnar Spreen
Keyword(s):  
Time Series ◽  
Sea Ice ◽  
Global Climate ◽  
Ice Cover ◽  
Cold Season ◽  
Arctic Sea Ice ◽  
Weddell Sea ◽  
Detailed Knowledge ◽  
The Antarctic ◽  
Multiyear Ice

<p>The changing sea ice cover of polar seas is of key importance for the exchange of heat and moisture between atmosphere and ocean and hence for weather and climate, and in addition, the sea ice and its long-term changes are  an indicator for global change.  In order to properly understand and model the evolution of the sea ice cover and its interaction with the global climate system, we need detailed knowledge about sea ice, i.e., not only its extent, but also, e.g., its thickness and its type.</p> <p>We can broadly distinguish a few different sea ice types that have different dynamic and thermodynamic properties, namely: young ice (YI, thin/smooth new ice), first-year ice (FYI, formed during one cold season), and multiyear ice (MYI, which has survived at least one melt season). The  latter is of particular interest as it is usually thicker than other ice types (thus, takes more time to melt), much less saline, and may accommodate a unique ecosystem. Sea ice types in the Antarctic, until recently, have not been monitored much because of the lack of appropriate remote  sensing methods. While the Antarctic sea ice is greatly dominated by FYI, there are, nevertheless, considerable amounts of MYI, in particular in the Weddell Sea.</p> <p>We have recently adapted an algorithm for the detection of Arctic sea ice types for application in the Antarctic. The algorithm uses data from space-borne microwave radiometers and scatterometers as input. So far we have compiled a time series of daily Antarctic MYI data (and also an estimate of YI and FYI) data at a spatial resolution of 12.5 km, starting in 2013, but excluding the melt seasons when the algorithm does not work. Here give an overview of the data, showing, e.g., the quite large interannual variability of MYI and its evolution in the Weddell Sea, and discuss shortcomings of the algorithm and possible ways forward. The time series of daily Antarctic MYI data can in principle be extended backwards to the year 2000, when the used satellite data first became available, and with planned future satellite missions, it can be continued for years to come.</p>

scholarly journals Driving Forces of Circum-Antarctic Glacier and Ice Shelf Front Retreat over the Last Two Decades

2020 ◽  
Author(s):  
Celia A. Baumhoer ◽  
Andreas J. Dietz ◽  
Christof Kneisel ◽  
Heiko Paeth ◽  
Claudia Kuenzer
Keyword(s):  
Sea Ice ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Air Temperature ◽  
Environmental Variables ◽  
Sea Surface ◽  
Ice Shelf ◽  
Antarctic Ice Sheet ◽  
Ice Shelves ◽  
The Antarctic

Abstract. The safety band of Antarctica consisting of floating glacier tongues and ice shelves buttresses ice discharge of the Antarctic Ice Sheet. Recent disintegration events of ice shelves and glacier retreat indicate a weakening of this important safety band. Predicting calving front retreat is a real challenge due to complex ice dynamics in a data-scarce environment being unique for each ice shelf and glacier. We explore to what extent easy to access remote sensing and modelling data can help to define environmental conditions leading to calving front retreat. For the first time, we present a circum-Antarctic record of glacier and ice shelf front retreat over the last two decades in combination with environmental variables such as air temperature, sea ice days, snowmelt, sea surface temperature and wind direction. We find that the Antarctic ice sheet area shrank 29,618 ± 29 km2 in extent between 1997–2008 and gained an area of 7,108 ± 144.4 km2 between 2009 and 2018. Retreat concentrated along the Antarctic Peninsula and West Antarctica including the biggest ice shelves Ross and Ronne. Glacier and ice shelf retreat comes along with one or several changes in environmental variables. Decreasing sea ice days, intense snow melt, weakening easterlies and relative changes in sea surface temperature were identified as enabling factors for retreat. In contrast, relative increases in air temperature did not correlate with calving front retreat. To better understand drivers of glacier and ice shelf retreat it is of high importance to analyse the magnitude of basal melt through the intrusion of warm Circumpolar Deep Water (CDW) driven by strengthening westerlies and to further assess surface hydrology processes such as meltwater ponding, runoff and lake drainage.

scholarly journals Coastal-change and glaciological maps of Antarctica

1995 ◽  
Vol 21 ◽  
pp. 284-290 ◽  
Author(s):  
Richard S. Williams ◽  
Jane G. Ferrigno ◽  
Charles Swithinbank ◽  
Baerbel K. Lucchitta ◽  
Barbara A. Seekins
Keyword(s):  
Global Climate ◽  
Base Line ◽  
Ice Streams ◽  
Landsat Images ◽  
Ice Shelves ◽  
Coastal Mapping ◽  
Grounding Line ◽  
Polar Research Institute ◽  
The Antarctic

In spite of their importance to global climate and sea level, the mass balance of the Antarctic ice sheet and the dynamics of the coast of Antarctica are largely unknown. In 1990, the U.S. Geological Survey, in cooperation with the Scott Polar Research Institute. U.K., began a long-term coastal mapping project in Antarctica that is based on analysis of Landsat images and ancillary sources. The project has live objectives: (1) to determine coastline changes that have occurred between the mid-1970s and the late 1980s/early 1990s; (2) to establish an accurate base-line series of 24 1: 1 000 000 scale maps that define the glaciological characteristics of the coastline: (3) to determine velocities of outlet glaciers, ice streams and ice shelves: (4) to compile a comprehensive inventory of outlet glaciers and ice streams: and (5) to compile a 1: 5 000 000 scale map of Antarctica derived from the 24 maps. Analysis of images used in producing the first five of the 24 maps has shown that ice fronts, iceberg tongues and glacier tongues are the most dynamic and changeable features in the coastal regions of Antarctica. Seaward of the grounding line of outlet glaciers, ice streams and ice shelves, the floating margin is subject to frequent, large calving events and rapid flow. Although calving does occur along ice walls, the magnitude of their change on an annual to decadal basis is generally not discernible on Landsat images; therefore, ice walls can be used as relatively stable reference features for measuring other changes along the coast. Velocities of outlet glaciers, ice streams and ice shelves range from 0.1 to several kilometers per year.

Submarine landforms on the Weddell Sea shelf imaged at high resolution using AUVs

2020 ◽  
Author(s):  
Julian Dowdeswell ◽  
Christine Batchelor ◽  
Sasha Montelli ◽  
Dag Ottesen ◽  
Evelyn Dowdeswell ◽  
...  
Keyword(s):  
High Resolution ◽  
Autonomous Underwater Vehicles ◽  
Horizontal Resolution ◽  
Weddell Sea ◽  
Ice Shelves ◽  
Glacial Landform ◽  
Glacial Landforms ◽  
The Antarctic ◽  
The Last Glacial Maximum ◽  
The Last Glacial

<p>Multibeam echo-sounders were deployed from Autonomous Underwater Vehicles (AUVs) flying close to the seafloor of the Weddell Sea shelf in order to investiagte the glacial landforms there with a view to understanding processes and patterns associated with deglaciation from the Last Glacial Maximum on the eastern side of the Antarctic Peninsula. A horizontal resolution of 0.5 m (using conventional mulitbeam systems), and in some cases 0.05 m (using interferometric multibeam equipment), allowed delicate seafloor landforms to be mapped in several areas of the shelf beyond the Larsen C and former Larsen A and B ice shelves. A number of glacial landform assemblages were observed, including suites of delicate ridges associated with grounding-zone wedges and the grounding of icebergs on the shelf. These landforms are probably related to the action of tides moving the ice up and down through a series of tidal cycles. At the highest spatial resolution, individual dropstones derived from rain-out during the melting of floating ice were imaged clearly. Imaging the seafloor at such high resolution allows both very detailed descriptions of submarine landform morphology and also the complexity of such landforms and landform assemblages to be better understood, aiding the interpretation of the glacial and related processes that led to their formation.</p>

Recent glacial advance in the western Weddell Sea Sector driven by anomalous sea ice circulation

2020 ◽  
Author(s):  
Frazer Christie ◽  
Toby Benham ◽  
Julian Dowdeswell
Keyword(s):  
Sea Ice ◽  
Antarctic Peninsula ◽  
Ice Sheet ◽  
Weddell Sea ◽  
Landsat 8 ◽  
Ice Shelf ◽  
Total Contribution ◽  
Antarctic Ice Sheet ◽  
Ice Shelves ◽  
The Antarctic

<p>The Antarctic Peninsula is one of the most rapidly warming regions on Earth. There, the recent destabilization of the Larsen A and B ice shelves has been directly attributed to this warming, in concert with anomalous changes in ocean circulation. Having rapidly accelerated and retreated following the demise of Larsen A and B, the inland glaciers once feeding these ice shelves now form a significant proportion of Antarctica’s total contribution to global sea-level rise, and have become an exemplar for the fate of the wider Antarctic Ice Sheet under a changing climate. Together with other indicators of glaciological instability observable from satellites, abrupt pre-collapse changes in ice shelf terminus position are believed to have presaged the imminent disintegration of Larsen A and B, which necessitates the need for routine, close observation of this sector in order to accurately forecast the future stability of the Antarctic Peninsula Ice Sheet. To date, however, detailed records of ice terminus position along this region of Antarctica only span the observational period c.1950 to 2008, despite several significant changes to the coastline over the last decade, including the calving of giant iceberg A-68a from Larsen C Ice Shelf in 2017.</p><p>Here, we present high-resolution, annual records of ice terminus change along the entire western Weddell Sea Sector, extending southwards from the former Larsen A Ice Shelf on the eastern Antarctic Peninsula to the periphery of Filchner Ice Shelf. Terminus positions were recovered primarily from Sentinel-1a/b, TerraSAR-X and ALOS-PALSAR SAR imagery acquired over the period 2009-2019, and were supplemented with Sentinel-2a/b, Landsat 7 ETM+ and Landsat 8 OLI optical imagery across regions of complex terrain.</p><p>Confounding Antarctic Ice Sheet-wide trends of increased glacial recession and mass loss over the long-term satellite era, we detect glaciological advance along 83% of the ice shelves fringing the eastern Antarctic Peninsula between 2009 and 2019. With the exception of SCAR Inlet, where the advance of its terminus position is attributable to long-lasting ice dynamical processes following the disintegration of Larsen B, this phenomenon lies in close agreement with recent observations of unchanged or arrested rates of ice flow and thinning along the coastline. Global climate reanalysis and satellite passive-microwave records reveal that this spatially homogenous advance can be attributed to an enhanced buttressing effect imparted on the eastern Antarctic Peninsula’s ice shelves, governed primarily by regional-scale increases in the delivery and concentration of sea ice proximal to the coastline.</p>

scholarly journals Antarctic regional modelling of atmospheric, sea-ice and oceanic processes and validation with observations

2000 ◽  
Vol 31 ◽  
pp. 348-352 ◽  
Author(s):  
David A. Bailey ◽  
Amanda H. Lynch
Keyword(s):  
Sea Ice ◽  
Global Climate ◽  
Regional Climate ◽  
Climate System ◽  
The Arctic ◽  
Small Scale ◽  
Atmospheric Conditions ◽  
Regional Modelling ◽  
Climate System Model ◽  
The Antarctic

AbstractHigh-latitude interactions of local-scale processes in the atmosphere-ice-ocean system have effects on the local, Antarctic and global climate. Phenomena including polynyas and leads are examples of such interactions which, when combined, have a significant impact on larger scales. These small-scale features, which are typically parameterized in global models, can be explicitly simulated using high-resolution regional climate system models. As such, the study of these interactions is well suited to a regional model approach and is considered here using the Arctic Regional Climate System Model (ARCSyM). This model has been used for many simulations in the Arctic, and is now implemented for the Antarctic. Observations of such processes in the Antarctic are limited, which makes model validation difficult. However, using the best available observations for an annual cycle, we have determined a suite of model parameterization which allows us to reasonably simulate the Antarctic climate. This work considers a fine-resolution (20 km) simulation in the Cosmonaut Sea region, with the eventual goal of elucidating the mechanisms in the formation and maintenance of the sensible-heat polynya which is a regular occurrence in this area. It was found in an atmosphere-sea-ice simulation that the ocean plays an important role in regulating the sea-ice cover in this region in compensating for the cold atmospheric conditions.

scholarly journals Explicit and parametrised representation of under ice shelf seas in a z<sup>*</sup> coordinate ocean model

2017 ◽  
Author(s):  
Pierre Mathiot ◽  
Adrian Jenkins ◽  
Christopher Harris ◽  
Gurvan Madec
Keyword(s):  
Sea Ice ◽  
Continental Shelf ◽  
Weddell Sea ◽  
Depth Range ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Antarctic Continental Shelf ◽  
Shelf Seas ◽  
Ocean Properties ◽  
The Antarctic

Abstract. Ice shelf/ocean interactions are a major source of fresh water on the Antarctic continental shelf and have a strong impact on ocean properties, ocean circulation and sea ice. However, climate models based on the ocean/sea ice model NEMO currently do not include these interactions in any detail. The capability of explicitly simulating the circulation beneath ice shelves is introduced in the non-linear free surface model NEMO. Its implementation into the NEMO framework and its assessment in an idealised and realistic circum-Antarctic configuration is described in this study. Compared with the current prescription of ice shelf melting (i.e. at the surface) inclusion of open sub-ice-shelf leads to a decrease sea ice thickness along the coast, a weakening of the ocean stratification on the shelf, a decrease in salinity of HSSW on the Ross and Weddell Sea shelves and an increase in the strength of the gyres that circulate within the over-deepened basins on the West Antarctic continental shelf. Mimicking the under ice shelf seas overturning circulation by introducing the meltwater over the depth range of the ice shelf base, rather than at the surface is also tested. It yields similar improvements in the simulated ocean properties and circulation over the Antarctic continental shelf than the explicit ice shelf cavity representation. With the ice shelf cavities opened, the widely-used “3 equations” ice shelf melting formulation enables an interactive computation of melting that has been assessed. Comparison with observational estimates of ice shelf melting indicates realistic results for most ice shelves. However, melting rates for Amery, Getz and George VI ice shelves are considerably overestimated.

Causes and consequences of Southern Ocean change: the IPCC SROCC assessment

2020 ◽  
Author(s):  
Michael Meredith ◽  
Martin Sommerkorn ◽  
Sandra Cassotta ◽  
Chris Derksen ◽  
Alexey Ekaykin ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Sea Level ◽  
Ocean Circulation ◽  
Global Climate ◽  
Ice Sheets ◽  
The Arctic ◽  
Polar Regions ◽  
Ice Shelves

&lt;p&gt;Climate change in the polar regions exerts a profound influence both locally and over all of our planet.&amp;#160; Physical and ecosystem changes influence societies and economies, via factors that include food provision, transport and access to non-renewable resources.&amp;#160; Sea level, global climate and potentially mid-latitude weather are influenced by the changing polar regions, through coupled feedback processes, sea ice changes and the melting of snow and land-based ice sheets and glaciers.&lt;/p&gt;&lt;p&gt;Reflecting this importance, the IPCC Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) features a chapter highlighting past, ongoing and future change in the polar regions, the impacts of these changes, and the possible options for response.&amp;#160; The role of the polar oceans, both in determining the changes and impacts in the polar regions and in structuring the global influence, is an important component of this chapter.&lt;/p&gt;&lt;p&gt;With emphasis on the Southern Ocean and through comparison with the Arctic, this talk will outline key findings from the polar regions chapter of SROCC. It will synthesise the latest information on the rates, patterns and causes of changes in sea ice, ocean circulation and properties. It will assess cryospheric driving of ocean change from ice sheets, ice shelves and glaciers, and the role of the oceans in determining the past and future evolutions of polar land-based ice. The implications of these changes for climate, ecosystems, sea level and the global system will be outlined.&lt;/p&gt;

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