Near-coastal circum-Antarctic iceberg size distributions determined from Synthetic Aperture Radar images

Wesche, Christine; Dierking, Wolfgang

doi:10.1016/j.rse.2014.10.025

Cited by 36 publications

(71 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Approximately 80% of ice islands in the spatial and temporal snapshots were <10 km 2 (Figures and ). This supports previous findings that most mass will be contained within a few large ice islands, while the ice island population will be dominated by smaller ice islands, which are difficult to detect in SAR imagery (Rackow et al, ; Saper, ; Wesche & Dierking, ). Therefore, these smaller ice islands, icebergs, bergy bits, and growlers pose greater risks to offshore operations such as shipping and resource extraction (Saper, ).…”

Section: Discussionsupporting

confidence: 90%

The Aftermath of Petermann Glacier Calving Events (2008–2012): Ice Island Size Distributions and Meltwater Dispersal

et al. 2018

View full text Add to dashboard Cite

Three large calving events occurred at Petermann Glacier in northwest Greenland between 2008 and 2012 that generated ice islands (large tabular icebergs) that ranged from ~30 to 300 km2 in areal extent. Ice islands are known to deteriorate, via fracture and melt, during their drift through regional water bodies where they pose a potential risk to offshore resource extraction operations and disperse freshwater from the Greenland Ice Sheet. This study presents the first analysis of the deterioration occurring across the flux of ice islands that travel between Nares Strait and the North Atlantic after Petermann Glacier calving events. The evolution of Petermann ice island size distributions was evaluated, and the spatial dispersal of meltwater was quantified, through analyses that utilized the newly developed Canadian Ice Island Drift, Deterioration and Detection Database. Size‐frequency distributions remained relatively consistent, both spatially and temporally, and were well fit by power law models with slopes of approximately −1.7. This suggested that fracture was an important process by which the Petermann ice islands deteriorated, regardless of elapsed time or distance from the glacier. Ice island meltwater fluxes into the Baffin Island and Labrador currents were not large enough to slow down the Atlantic Meridional Overturning Circulation by weakening deep‐water convection in the Labrador Sea. However, augmented meltwater input was calculated within Petermann Fjord (2.0 mSv) and in the vicinity of grounding locations (0.4 mSv). Further research is necessary to better understand how this freshwater alters fjord circulation and influences the composition of local ocean waters.

show abstract

Section: Discussionsupporting

confidence: 90%

The Aftermath of Petermann Glacier Calving Events (2008–2012): Ice Island Size Distributions and Meltwater Dispersal

et al. 2018

View full text Add to dashboard Cite

show abstract

“…However, very few studies proposed a size distribution covering the whole range of iceberg size. Using a limited data set of SAR images from the Radarsat‐1 Antarctic Mapping Project (RAMP) that are snapshots taken from September to October 1997 and are restricted to the near‐coastal zone, Wesche and Dierking [] detected 6912 icebergs larger than 0.3 km 2 . They estimated a size distribution by surface area ranges with 71.9% of icebergs from 0.3 to 1 km 2 , 26.0% 1–10 km 2 , 1.8% 10–100 km 2 , 0.2% 100–1000 km 2 , and 0.1% 1000–10,000 km 2 .…”

Section: Unified Iceberg Size Distributionmentioning

confidence: 99%

“…The −1.52 power law approximation gives a size distribution by range of 77% for icebergs <1 km 2 , 17% for 1–10 km 2 , 4.8% for 10–100 km 2 , 1.5% for 100–1000 km 2 , and 0.4% for 1000–10,000 km 2 (see Figure ). This distribution agrees relatively well to the Wesche and Dierking [] one. However, it has less icebergs in the 1–10 km 2 range and more icebergs larger than 10 km 2 .…”

Section: Unified Iceberg Size Distributionmentioning

confidence: 99%

Antarctic icebergs distributions 1992–2014

et al. 2016

View full text Add to dashboard Cite

Basal melting of floating ice shelves and iceberg calving constitute the two almost equal paths of freshwater flux between the Antarctic ice cap and the Southern Ocean. The largest icebergs (>100 km2) transport most of the ice volume but their basal melting is small compared to their breaking into smaller icebergs that constitute thus the major vector of freshwater. The archives of nine altimeters have been processed to create a database of small icebergs (<8 km2) within open water containing the positions, sizes, and volumes spanning the 1992–2014 period. The intercalibrated monthly ice volumes from the different altimeters have been merged in a homogeneous 23 year climatology. The iceberg size distribution, covering the 0.1–10,000 km2 range, estimated by combining small and large icebergs size measurements follows well a power law of slope −1.52 ± 0.32 close to the −3/2 laws observed and modeled for brittle fragmentation. The global volume of ice and its distribution between the ocean basins present a very strong interannual variability only partially explained by the number of large icebergs. Indeed, vast zones of the Southern Ocean free of large icebergs are largely populated by small iceberg drifting over thousands of kilometers. The correlation between the global small and large icebergs volumes shows that small icebergs are mainly generated by large ones breaking. Drifting and trapping by sea ice can transport small icebergs for long period and distances. Small icebergs act as an ice diffuse process along large icebergs trajectories while sea ice trapping acts as a buffer delaying melting.

show abstract

“…Romanov et al (2008) and Romanov et al (2012) focused on spatial distribution and multiyear variability of icebergs in the Atlantic-Indian sector of the Southern Ocean and the general distribution in terms of shape and size. Wesche and Dierking (2015) presented the spatial distribution of icebergs around Antarctica in near-coastal waters for the year 1997 in relation to the type of calving fronts. In a series of papers (Bouhier et al, 2018;Tournadre et al, 2008Tournadre et al, , 2012Tournadre et al, , 2016, the recent iceberg distribution in open water for the whole Southern Ocean was shown, discussing size distribution, melting, and fragmentation.…”

Section: Introductionmentioning

confidence: 99%

“…gov/Main_Products.htm, last visit 28.03.2019) and the Brigham Young University (http://www.scp.byu.edu/ data/iceberg/, last visit 28.03.2019) have been actively detecting and tracking icebergs larger than 10 nautical miles (longest axis) in the Southern Ocean using spaceborne scatterometer (Stuart & Long, 2011). Also, previous studies have presented iceberg distributions for different regions of the Southern Ocean applying distinct approaches, namely, observational data (Jacka & Giles, 2007;Romanov et al, 2012), satellite altimetry (Tournadre et al, , 2012(Tournadre et al, , 2008, numerical models (Gladstone, 2001;Rackow et al, 2017;Stern et al, 2016), or Synthetic Aperture Radar (SAR; Silva et al, 2006;Wesche & Dierking, 2015). SAR bridges a gap between observational, altimetry, and scatterometer methods, since it enables detection of icebergs from lengths of a few tens of meters up to several kilometers even during polar night and independent of the prevailing cloud conditions.…”

Section: Introductionmentioning

confidence: 99%

Three Years of Near‐Coastal Antarctic Iceberg Distribution From a Machine Learning Approach Applied to SAR Imagery

et al. 2019

Self Cite

View full text Add to dashboard Cite

Mass loss around the Antarctic Ice Sheet is driven by basal melting and iceberg calving, which constitute the two dominant paths of freshwater flux into the Southern Ocean. Although of similar magnitude, icebergs play an important and still not fully understood role in the balance of heat and freshwater around Antarctica. This lack of understanding is partly due to operational difficulties in large-scale monitoring in polar regions, despite observational and remote sensing efforts. In this study, a novel machine learning approach, augmented by visual inspection, was applied to three Synthetic Aperture Radar (SAR) mosaics of the whole Antarctic continent and its adjacent coastal zone. Although originally intended for a mapping of the Antarctic continent, the SAR mosaics allow us to document the evolution and distribution of the size (and mass) of icebergs in the pan-Antarctic near-coastal zone for the years 1997, 2000, and 2008. Our novel algorithm identified 7,649 icebergs in 1997, 13,712 icebergs in 2000, and 7,246 icebergs in 2008 with surface areas between 0.1 and 4,567.82 km 2 and total masses of 4,641.53, 6,862.81, and 5,263.69 Gt, respectively. Large regional variability was observed, although a zonal pattern distribution is present. This has implications for future climate modeling studies that try to estimate the freshwater flux from melting icebergs, which demands a realistic representation of the interannually varying near-coastal iceberg pattern to initialize the simulations. Plain Language SummaryWhen icebergs melt in the Southern Ocean, they cool the surrounding ocean. They also distribute freshwater, which potentially impacts the circulation, biological activity, sea-ice cover, and the formation of the densest waters of the world's oceans. However, all these influences are not fully understood because we are lacking reliable methods to detect icebergs from space via satellites. This study has the main objective to determine how iceberg mass is distributed in the coastal zone around the Antarctic continent and how this distribution changes between individual years. We show that a novel machine learning approach can be applied to this problem, which is capable to identify icebergs in satellite images of the near-coastal ocean region almost automatically. The method also works in severe conditions, e.g. when the icebergs are affected by ocean waves or when they are surrounded by sea ice. Our results complement the ongoing discussion about the distribution of Antarctic icebergs in open-ocean regions that are not affected by sea ice. The resulting data can also be used in computer models that simulate the input of iceberg freshwater into the ocean.

show abstract

Near-coastal circum-Antarctic iceberg size distributions determined from Synthetic Aperture Radar images

Cited by 36 publications

References 20 publications

The Aftermath of Petermann Glacier Calving Events (2008–2012): Ice Island Size Distributions and Meltwater Dispersal

The Aftermath of Petermann Glacier Calving Events (2008–2012): Ice Island Size Distributions and Meltwater Dispersal

Antarctic icebergs distributions 1992–2014

Three Years of Near‐Coastal Antarctic Iceberg Distribution From a Machine Learning Approach Applied to SAR Imagery

Contact Info

Product

Resources

About