Iceberg Scouring Research Articles

Geophysical evidence of deep-keeled icebergs on the Rockall Bank, Northeast Atlantic Ocean

High resolution multibeam swath bathymetric data acquired from the Rockall Bank reveal an abundance of linear to slightly sinuous seabed incisions. These features, interpreted as relict iceberg scours, provide for the first time evidence that the Rockall Bank was intensively scoured by iceberg keels. While the shallower portion of the Rockall Bank lacks evidence of iceberg scouring, on the western and southern flanks (between 250 and 450m water depth) the seabed is almost completely covered by thousands of cross-cutting scours. More isolated scours, up to 800m wide and 25km long are also observed down to nearly 600m water depth. Based on a full glacial sea level low stand of 120m, these isolated scour marks must have been carved by gigantic icebergs with keels up to 500m deep and able to create incisions up to 15m deep in the seabed. Analysis of scour orientation, length, width, and depth indicates that these mega-icebergs were likely calved from large, fast-flowing ice sheet outlets draining circum-North Atlantic ice sheets. Prevailing scour orientations suggest a number of possible ice sheet sources, including southeast and southern Greenland and the Donegal-Barra ice stream of the last British–Irish Ice Sheet. The bimodal distribution of the scour depth observed across the Rockall Bank suggest either different icebergs provenances or physical and climatic controls on icebergs draft.

Reduced survival of Antarctic benthos linked to climate-induced iceberg scouring

The West Antarctic Peninsula has experienced rapid warming in recent decades. One of the effects has been a loss of the ‘fast-ice’ skin, or frozen layer, that forms on the sea surface each winter and reduces seabed scouring. A study now links increased seabed scouring over the past 25 years to higher benthic mortality, with implications for the region’s biodiversity.

Patterns of hydroid (Cnidaria, Hydrozoa) species richness and distribution in an Arctic glaciated fjord

The consequences of global warming are particularly evident in high polar areas. Deglaciation phenomenon—negative mass balance of Svalbard glaciers and recession of tidal glaciers—results in landscape and shoreline change. These areas of very dynamic conditions are now open for primary colonists, among them hydroids, typical early colonists of the vacant substratum. This study aims to explore the patterns of Hydrozoan diversity and distribution in Hornsund (west Spitsbergen). Hydroids associated with shallow water kelp beds as well as those occurring on deeper subtidal soft bottom were collected at sites located along gradients of glacial disturbance (i.e., high mineral sedimentation, ice-berg scouring). Samples were collected by scuba diving (three sites of different distance to active tidal glaciers), van Veen grabs (two sites located in the inner and outer fjord basin), and dredges taken from along a fjord transect. Hydroid diversity differed significantly between sites located in the vicinity of glaciers fronts in glaciated bays and sites comparatively free from glacier disturbance. Glacial disturbance results in low frequencies of occurrence and high levels of rarity of hydroids at sites located close to glacier fronts. The species richness of hydroids colonizing the hard substrate elements present in deeper subtidal decreases along the fjord axis (i.e., along the glacial sedimentation gradient).

Demersal ichthyofaunal shelf communities from the Dumont d’Urville Sea (East Antarctica)

The RSV Aurora Australis survey allowed the first comprehensive study of the demersal ichthyofaunal environment and of the diversity of the Dumont d’Urville Sea. We observed a high dominance of the Notothenioidei in both the number of species and in integrated abundances. The Nototheniidae was the most abundant family with 44.7% of the total integrated abundance, followed by Bathydraconidae (18.8%). Trematomus eulepidotus was the dominant species with 19.9% of the total individuals catch. Nevertheless, 43 of the 53 species caught could be considered as very rare. The Bathydraconidae was the most diversified family with 11 species caught. The highest integrated abundances of fish were found from 400 to 800 m. Well-structured species communities were observed, with high species richness from 570 to 681 m. The richest zones were located along the basins and along their upper-sides. Statistical analyses indicated large-scale spatial patterns in species composition, with clear differences in fish communities from the continental slopes, the basins and on the shelf. At a finer spatial scale, the current in the George V Basin and iceberg scouring on the banks and their sides tended to create locally heterogeneous small-scale habitats. We suggest that the glacial history and the structured habitats allowed successive colonisations of the seabed by demersal fish.

The impact of sediment deposition and iceberg scour on the Antarctic soft shell clam Laternula elliptica at King George Island, Antarctica

AbstractRecent rapid changes of air temperature on the western side of the Antarctic Peninsula results in increased sediment discharge and ice scouring frequencies in coastal regions. These changes are bound to especially affect slow growing, sessile filter feeders such as the Antarctic bivalve, Laternula elliptica, a long-lived and abundant key species with circumpolar distribution. We investigated the effect of sedimentation and ice scouring on small/young and large/old individuals at two closely located stations, distinctly influenced by both types of disturbance. Small individuals dealt better with disturbance in terms of their respiratory response to sediment exposure, reburrowing ability, and survival after injury, compared to larger animals. At the more disturbed station L. elliptica population density was lower, but larger animals reburrowed faster after iceberg disturbance and reduced their metabolic rate under strong sediment coverage, compared to larger animals of the less disturbed station, indicating that an adaptation or learning response to both types of disturbance may be possible. Smaller individuals were not influenced. Laternula elliptica seems capable of coping with the rapidly changing environmental conditions. Due to a decrease in population density and mean population lifespan, L. elliptica could however lose its key role in the bentho-pelagic carbon flux in areas of high sediment deposition.

Geomorphology of the Irish Rockall Trough, North Atlantic Ocean, mapped from multibeam bathymetric and backscatter Data

Please click here to download the map associated with this article. Multibeam echosounder data collected by the Irish National Seabed Survey (INSS) between 2000 and 2001 in the Rockall Trough have been used by many projects to analyze the geomorphology and the sedimentary processes of the margins of the Trough. However, due to the low spatial resolution of 150–250 m and the amount of artefacts still embedded in the publicly available data, many geomorphological features have been overlooked. This paper shows that the same multibeam dataset can provide more detailed information on seabed processes when the latest hydrographic and backscatter post-processing techniques are used to reduce data artefacts and improve data quality and spatial resolution. The resulting map, presented here at a scale of 1:450,000, is based on a semi-automatic and manual interpretation of geomorphological features highlighted using a new and improved 30 m bathymetric grid and a multibeam backscatter mosaic obtained using the GEOCODER post-processing algorithm. Overall, the map shows a complex sedimentological scenario where the Rockall Bank Mass Flow failure, the Donegal-Barra trough-mouth fan, along slope structures such as the Feni Contourite Drift and the Porcupine moat dominate the Rockall Trough flanks and basin floor. Smaller features such as canyon and gully systems, escarpments, coral mounds, volcanic mounds and iceberg scours have also been mapped in detail. In addition, the interpretation of the backscatter mosaic allows for the first time the identification of depositional lobes generated by downslope mass transport and canyon drainage systems, particularly where these features completely lose their bathymetric expression.

Deep draft icebergs from the Barents Ice Sheet during MIS 6 are consistent with erosional evidence from the Lomonosov Ridge, central Arctic

Iceberg scour marks on the Lomonosov Ridge in the central Arctic imply that bergs with drafts exceeding 850 m once existed in the Arctic, whereas similar erosion patterns observed on the Yermak Plateau suggest that some of these deep‐keeled icebergs exited the Arctic through the Fram Strait into the Nordic Seas. An intermediate complexity climate model with a dynamic and thermodynamic iceberg model is used to simulate the collapse of the Barents Ice Sheet during MIS 6 with the purpose of investigating if deep‐draft “mega”‐icebergs can reach and ground on the Lomonosov Ridge. A number of simulations with different iceberg sizes show that deep‐draft bergs seeded from near the Franz Victoria Trough could indeed have reached the Ridge, whereas other bergs crossed the Yermak Plateau and exited through the Fram Strait. The draft of the bergs mainly determines the trajectory, with only minor influence from the mass, and length and width of the bergs. This work is consistent with previous speculation that these icebergs originated from the disintegration of the Barents Ice Sheet during Marine Isotope Stage 6 (MIS 6; 140 ka BP), but suggests their origin was more likely to be from the western, rather than eastern, major ice stream of that ice sheet. The long‐term impact on the overturning circulation from melting icebergs is more severe than that from a freshwater pulse of equivalent magnitude, and a correct representation of icebergs in paleoclimate models is therefore of importance.

Submarine landforms and shallow acoustic stratigraphy of a 400 km-long fjord-shelf-slope transect, Kangerlussuaq margin, East Greenland

Kangerlussuaq Fjord is a relatively uniform, steep-walled basin, whose floor has an almost smooth surface. Debris is supplied mainly from icebergs from the fast-flowing Kangerlussuaq Glacier. Sedimentation after iceberg release from multi-year sea ice is mainly by rain-out of fine-grained englacial debris. Streamlined glacial lineations and drumlins were produced at the sedimentary bed of an ice sheet that expanded into Kangerlussuaq Trough at the Last Glacial Maximum (LGM). Bedrock channels and crescentic overdeepenings indicate warm-based ice and free water beneath parts of the former ice sheet. Cross-cutting iceberg scour marks, which characterise outer Kangerlussuaq shelf, were produced not only during deglaciation, but also occasionally through the Holocene by deep-keeled icebergs from further north in East Greenland. The outward-convex contours of the shelf edge and slope beyond Kangerlussuaq Trough, and debris flows on the slope, suggest a glacier-influenced high-latitude fan. The distribution of streamlined subglacial landforms demonstrates that the Greenland Ice Sheet extended throughout Kangerlussuaq Fjord and reached at least 200 km across the shelf in Kangerlussuaq Trough at the LGM. Streamlined landform orientation indicates ice flow from the interior of Greenland down the axis of Kangerlussuaq Trough. There is little evidence for discrete sedimentary depocentres in the trough, implying that ice probably retreated rapidly from the outer and mid shelf during deglaciation.

Ice keel seabed features in marine channels of the central Canadian Arctic Archipelago: evidence for former ice streams and iceberg scouring

The study area lies within the central part of the Canadian Arctic Archipelago; a region that was covered by the Laurentide Ice Sheet during the Late Wisconsinan glaciation and earlier. Multibeam imagery from widely spaced transects indicates the presence of linear groove and ridge features on the seabed at several localities in Peel Sound, Franklin Strait, northern Larsen Sound, and within M’Clintock Channel. These lineations resemble features in Antarctica and in several formerly glaciated regions that have been interpreted to be sole marks emplaced beneath fast-flowing ice streams. Based on these analogies, a similar origin is inferred for the lineations on the channel floors within the study area The lineations are oriented parallel to the channel axes and margins. They occur on all transects within the bathymetrically deeper area at the junction of Franklin Strait and Peel Sound. Northward in Peel Sound they occur extensively on the western and central transects, and more locally on the eastern transect. Their north-south orientation is normal to that of glacial flow features on Somerset Island and most of eastern Prince of Wales Island, which border Peel Sound to the east and west, respectively. The trend of the lineations is northeasterly (parallel to the channel axis) in Franklin Strait and mainly northerly in Larsen Sound and M’Clintock Channel. Elsewhere, the seabed imagery commonly displays scours of various sizes and orientations created by the keels of icebergs. Seabed sediments revealed by 3.5 kHz sub-bottom profiles are interpreted to consist primarily of ice-contact sediments, that in part are thinly mantled by draped water lain sediments. The age of the lineations has not been established. Possibly their formation was coincident with an ice stream in the M’Clintock Channel – eastern Victoria Island region, which formed an ice shelf in Viscount Melville Sound that grounded on southern Melville and Byam Martin islands at ca. 10.4–9.6 14C ka BP Alternatively, they could result from later glacial events.

Community structure and benthic habitats across the George V Shelf, East Antarctica: Trends through space and time

Physical and biological characteristics of benthic communities are analysed from underwater video footage collected across the George V Shelf during the 2007/2008 CEAMARC voyage. Benthic habitats are strongly structured by physical processes operating over a range of temporal and spatial scales. Iceberg scouring recurs over timescales of years to centuries along shallower parts of the shelf, creating communities in various stages of maturity and recolonisation. Upwelling of modified circumpolar deep water (MCDW) onto the outer shelf and cross-shelf flow of high-salinity shelf water (HSSW) create spatial contrasts in nutrient and sediment supply, which are largely reflected in the distribution of deposit- and filter-feeding communities. Long-term cycles in the advance and retreat of icesheets (over millennial scales) and subsequent focussing of sediments in troughs such as the Mertz Drift create patches of consolidated and soft sediments, which also provide distinct habitats for colonisation by different biota. These physical processes of iceberg scouring, current regimes and depositional environments, in addition to water depth, are important factors in the structure of benthic communities across the George V Shelf. The modern shelf communities mapped in this study largely represent colonisation over the past 8000–12,000 years, following retreat of the icesheet and glaciers at the end of the last glaciation. Recolonisation on this shelf may have occurred from two sources: deep-sea environments and possible shelf refugia on the Mertz and Adélie Banks. However, any open-shelf area would have been subject to intense iceberg scouring. Understanding the timescales over which shelf communities have evolved and the physical factors which shape them will allow better prediction of the distribution of Antarctic shelf communities and their vulnerability to change. This knowledge can aid better management regimes for the Antarctic margin.

Ectosymbiosis associated with cidaroids (Echinodermata: Echinoidea) promotes benthic colonization of the seafloor in the Larsen Embayments, Western Antarctica

Ice-shelf collapses in the Larsen A and B embayments along the Weddell side of the Antarctic Peninsula resulted in new open-water areas that are likely reorganizing benthic communities. It is a natural laboratory to assess colonization of the sea bottom under new conditions. We tested the hypothesis that the epibionts associated to cidaroid echinoids could promote or enhance the colonization of hard surfaces. In fact, being vagile, cidaroids might improve dispersal capabilities of the sessile animals that are attached to their spines, e.g., promoting the colonization of areas where the fauna has been eradicated by iceberg scouring. If this hypothesis is correct, pioneer sessile species present locally on stones might have affinities with ectosymbionts on cidaroids, and the sessile fauna present both on cidaroids and stones should be more similar in the Larsen embayments than in undisturbed areas. We therefore compared sessile species living on cidaroids with those living on stones in three areas: Larsen A and B embayments and two undisturbed and geographically different areas, Atka Bay and Elephant Island. Overall, richness, evaluated as ‘morphotypes’ richness, was lower in the Larsen area than in other areas, but levels of species diversity were similar among the three zones. The estimate of similarity between assemblages (using the C 22 index of Chao et al., 2008) also suggests that cidaroid epibionts are either species-specific or specific to cidaroids, while the composition of sessile fauna on stones is more variable and probably dependent on local factors. In the two undisturbed areas, sessile fauna are highly different between stones and cidaroids. This contrasts with the Larsen embayments where cidaroids share more than 80% of epibionts with the surrounding stones. These results suggest that ectosymbioses linked to cidaroids strongly contribute to benthic colonization of the seafloor in the Larsen enbayments. With time, secondary successions are expected to occur, increasing the difference between epibiotic communities on cidaroids and those on stones, and lead to the situations observed in unperturbed sites.

Physical controls on deep water coral communities on the George V Land slope, East Antarctica

AbstractDense coral-sponge communities on the upper continental slope at 570–950 m off George V Land, East Antarctica have been identified as Vulnerable Marine Ecosystems. The challenge is now to understand their probable distribution on other parts of the Antarctic margin. We propose three main factors governing their distribution on the George V margin: 1) their depth in relation to iceberg scouring, 2) the flow of organic-rich bottom waters, and 3) their location at the head of shelf cutting canyons. Icebergs scour to 500 m in this region and the lack of such disturbance is a probable factor allowing the growth of rich benthic ecosystems. In addition, the richest communities are found in the heads of canyons which receive descending plumes of Antarctic Bottom Water formed on the George V shelf, which could entrain abundant food for the benthos. The canyons harbouring rich benthos are also those that cut the shelf break. Such canyons are known sites of high productivity in other areas due to strong current flow and increased mixing with shelf waters, and the abrupt, complex topography. These proposed mechanisms provide a framework for the identification of areas where there is a higher likelihood of encountering these Vulnerable Marine Ecosystems.

Glacial and glacially-related features on the continental margin of northwest Ireland mapped from marine geophysical data

Please click here to download the map associated with this article. Despite over a century of research, reconstructions of the western margin of the last British-Irish Ice Sheet remain controversial. This is mainly because the ice sheet extended offshore onto the continental shelf and therefore significant portions of the glacial record are below present sea level. The availability of high resolution multibeam swath bathymetric and geophysical sub-bottom data for over ∼30,000 km2 of the northwest Irish continental margin (between 55°40′ and 54°18′ N, and 7°50′ and 11°4′ W) has made it possible to map glacial features on the continental shelf and glacially-related features on the continental slope and rise. The resulting map, presented here at a scale of 1:260,000, shows that the major glacial features consist of subglacial bedforms and nested arcuate moraines of different orientations across the width of the shelf. Distal to these moraines, the outermost shelf and upper slope are crossed by subparallel and cross-cutting furrows created by iceberg scouring and meltwater discharge at the ice margin. A well-developed system of gullies and canyons and frequent escarpments incise the continental slope. Several large depositional lobes, likely related to the delivery of vast amount of sediment at the ice margin are found in inter-canyon areas and at the base of the slope. Collectively these data show an extensive ice sheet margin across the entire shelf and sedimentation on the continental margin was greatly affected by the presence of the ice margin at the shelf edge.

The glacial sequence at Killiney, SE Ireland: terrestrial deglaciation and polyphase glacitectonic deformation

Depositional conditions of a complexly deformed glacigenic sequence at Killiney Bay, on the west-central margin of the Irish Sea are reconstructed. Deformation geometries provide conclusive evidence for polyphase glacitectonic deformation generated by terrestrial ice sheets. They are dominated by pure shear, simple shear and compressional deformation styles with abundant evidence for glacitectonic induced fracturing and hydrofracturing. There is no evidence of subaqueous sediment flow-induced deformation and impact deformation (iceberg scouring, rained out clasts). Glacigenic diamicton facies associations (FA's) are interpreted as glacitectonically stacked diachroneous units younging laterally away from palaeo-ice margins. Simultaneous deposition of proximal overconsolidated subglacial tills and distal low viscosity flowtills occurred, with the latter being deformed during re-advances. Structural chronology of deformation styles demonstrates polyphase deformation of tills, where glacial overriding produced overconsolidated and polyphase deformed subglacial tills from sediments initially deposited as low viscosity flowtills. It is proposed that relatively late during deglaciation, after retreat of a grounded Irish Sea Ice Sheet, Midland Ice invaded the area and deformed and reworked recessional Irish Sea Ice sequences. Deformation of these recessional sequences led to a heterogeneous stack of polyphase deformed glacigenic sediments with abundant hydrofracturing. The Killiney Bay sequence and other sequences in the Southern Irish Sea Basin demonstrate that MIS 2 deglaciation took place under terrestrial conditions with lower relative sea levels than present.

Probabilistic pipeline burial analysis for protection against ice scour

Abstract A probabilistic burial analysis for protection against iceberg scouring of the seabed is presented for a hypothetical pipeline on the Grand Banks off Canada's east coast. The analysis procedure combines a probabilistic characterization of the iceberg scour regime with a deterministic analysis of pipeline stress/strain response for a range of iceberg scour widths, depths and iceberg keel/pipeline crown clearances, allowing a pipeline burial depth to be defined that satisfies specified stress/strain limits and target reliability levels.

Seafloor evidence for palaeo‐ice streaming and calving of the grounded Irish Sea Ice Stream: Implications for the interpretation of its final deglaciation phase

High resolution swath bathymetry data reveal a previously glaciated submarine terrain 20 km offshore Anglesey, north Wales, UK. The detailed documentation of remarkably well‐preserved subglacial and ice‐marginal bedforms provides evidence for a grounded part of the Irish Sea Ice Stream in a phase of deglaciation. The observed ribbed moraines, drumlins, flutes and eskers indicate a converging ice flow to the west, which then turns south into the deeper central Irish Sea Basin. Using the relative position of the bedforms, their spatial distribution and the morphological resemblance with bedforms described in the literature, this subglacial terrain is interpreted as representing a transition zone of frozen to thawed bed conditions during deglaciation, with an eastwards migrating thawing front that partly altered the edge of the surveyed ribbed moraine field by drumlinization. The abundant De Geer moraines and iceberg scour marks superimposed on drumlins and flutes reveal that the final retreat of the grounded ice margin in the surveyed area terminated into a water‐mass with extensive iceberg calving. As the glacial terrain is well preserved, no significant burial has taken place, either by glacially or terrestrially derived sediment. The strong tidal currents at present keep the submarine terrain swept clean of contemporary sediment cover.

Identification and dating of a key Late Pleistocene stratigraphic unit in the St. Lawrence Estuary and Gulf (Eastern Canada)

A recently acquired ∼8 m-long sediment core along with high-resolution seismic reflection and subbottom profiler sections allowed the identification, characterization and dating of a widespread seismic unit extending from the head of the Laurentian Channel (Lower St. Lawrence Estuary) to Honguedo Strait (Gulf of St. Lawrence), Eastern Canada. This seismic unit (labelled unit 2) is characterized by a series of parallel high-amplitude reflections with thicknesses ranging from 68 m near the head of the Laurentian Channel to <5 m in Honguedo Strait. This seismic unit is generally observed below a very thick sequence of postglacial sediments that can reach >250 m in the St. Lawrence Estuary, leaving it very difficult to be reached by conventional coring operations. Here, we reveal how we were able to trace and core this seismic unit in an area where it lays closer to the seafloor near the southern wall of the Laurentian Channel in the Lower St. Lawrence Estuary. This seismic unit consists of two sedimentary facies: sandy mud including ice-rafted debris (IRD) underlying faintly laminated to homogenous and plastic silty clays. Based on the sedimentary facies, we interpret the upper clays as ice-distal glaciomarine sediments and the lower sandier sediments as ice-proximal glaciomarine sediments. This interpretation is further supported by the fact that no seismic nor sediment facies present above seismic unit 2 throughout the Estuary and Gulf of St. Lawrence can be linked to glacial (i.e., ice-contact sediments such as till, moraines, esker, etc) sediments. Seismic unit 2 is highly disturbed by iceberg scouring in the Gulf of St. Lawrence where it is found at shallower depths, indicating that it was deposited during deglaciation. The available AMS 14C dates obtained in the ice-proximal glaciomarine sediments indicate that the lower part of seismic unit 2 was deposited during local re-advances or stillstands of the Laurentide Ice Sheet margins in the Goldthwait Sea that began at or before the Younger Dryas cold event (11 100–10 000 yr BP) and that seismic unit 2 can be used as a chronostratigraphic marker throughout the St. Lawrence Estuary and northwestern Gulf of St Lawrence.

Factors influencing hydroids (Cnidaria: Hydrozoa) biodiversity and distribution in Arctic kelp forest

The biodiversity and distribution patterns of epiphytic hydroids were studied in kelp forests (composed of Laminaria digitata, Saccharina latissima and Alaria esculenta) located in an Arctic glaciated fiord (Hornsund, west Spitsbergen). In total, twenty-eight species were found colonizing algae, stones connected to holdfast, and overgrowing the surface of other animals associated with kelps. The characteristics of the algal host (e.g. algae species, age, rhizoid volume or biomass) did not show any effect upon hydroid species richness or species composition. High hydroid biodiversity was strongly dependent on microsubstrate heterogeneity. The highest biodiversity as well as frequency of hydroid occurrence were noted at a site located furthest from the glacier and characterized by the lowest sediment concentration and sedimentation rate. Sexual reproduction also seemed to be inhibited by glacier-derived disturbance. Of ten fertile species found at the ‘clearest’ site only two were fertile at sites under the strong influence of such perturbations. Potential physical drivers of species occurrence were linked to the activity of tidal glaciers, particularly to high loads of mineral sedimentation and iceberg scouring.

A numerical model of iceberg scour

A numerical model of iceberg seabed scour is presented. Deformation of the seabed soil follows a Mohr–Coulomb yield criterion, and a pressure–solids volume fraction relationship. The model employs a Particle-In-Cell (PIC) advection scheme, which is suited to dealing with large displacements and discontinuities. Simulations addressed cases of two-dimensional deformation caused by a moving rigid indentor, representing an iceberg. The resulting deformation patterns display expected failure zones and the development of shear layers. The simulations examined the dependence of stresses on scour depth, soil properties, compaction and scour velocity. Comparisons with experimental measurements are also carried out. The results show that the mean normal stress on the iceberg increased with deeper scours and the angle of internal friction of the sand. A decay of stresses was observed in the seabed under the scouring iceberg with higher stress values observed for higher initial solids volume fraction of the sand.

Polychaete assemblages of the northwestern Ross Sea shelf: worming out the environmental drivers of Antarctic macrobenthic assemblage composition

We have limited understanding of which environmental factors structure the distribution patterns and composition of Antarctic macrobenthos assemblages, and the spatial scales on which such factors operate. In 2004, the “BioRoss Survey” was conducted on the northwestern Ross Sea shelf between Cape Adare and Cape Hallett in depths of 50–750 m to describe and quantify the assemblage patterns of benthic macroinvertebrates. In order to determine the influence of primary productivity, disturbance and habitat heterogeneity on the distribution and composition of the macrofaunal assemblages, polychaete data derived from 52 grab samples were analysed. Although differences in the composition of polychaete assemblages among different sampling transects and depth strata were not particularly pronounced (yet statistically significant), the results suggested that large-scale differences in both primary productivity and iceberg disturbance influence distribution patterns. The combination of sediment chl a content, sorting coefficient, sponge spicule content and distance to the nearest iceberg scour best explained polychaete assemblage patterns. This finding supports previous contentions that multiple environmental drivers working at varying scales influence Antarctic shelf assemblages. The results do not supply support for a pronounced decoupling of pelagic and benthic systems, as has been suggested by another study of deeper water benthic assemblages on the Ross Sea shelf.