Arctic Seafloor Research Articles

Marine litter on deep Arctic seafloor continues to increase and spreads to the North at the HAUSGARTEN observatory

The increased global production of plastics has been mirrored by greater accumulations of plastic litter in marine environments worldwide. Global plastic litter estimates based on field observations account only for 1% of the total volumes of plastic assumed to enter the marine ecosystem from land, raising again the question ‘Where is all the plastic? ’. Scant information exists on temporal trends on litter transport and litter accumulation on the deep seafloor. Here, we present the results of photographic time-series surveys indicating a strong increase in marine litter over the period of 2002–2014 at two stations of the HAUSGARTEN observatory in the Arctic (2500m depth).Plastic accounted for the highest proportion (47%) of litter recorded at HAUSGARTEN for the whole study period. When the most southern station was considered separately, the proportion of plastic items was even higher (65%). Increasing quantities of small plastics raise concerns about fragmentation and future microplastic contamination. Analysis of litter types and sizes indicate temporal and spatial differences in the transport pathways to the deep sea for different categories of litter. Litter densities were positively correlated with the counts of ship entering harbour at Longyearbyen, the number of active fishing vessels and extent of summer sea ice. Sea ice may act as a transport vehicle for entrained litter, being released during periods of melting. The receding sea ice coverage associated with global change has opened hitherto largely inaccessible environments to humans and the impacts of tourism, industrial activities including shipping and fisheries, all of which are potential sources of marine litter.

Bacterial biogeography influenced by shelf-basin exchange in the Arctic surface sediment at the Chukchi Borderland.

It has been known that continental shelves around the Arctic Ocean play a major role in the ventilation of the deep basins as a consequence of shelf-basin exchange. In the present study, we found that bacterial assemblage of the surface sediment was different from that of seawater while seawater harboured local bacterial assemblages in response to the Arctic hydrography. This finding suggests that the Arctic seafloor sediments may have distinctive bacterial biogeography. Moreover, the distribution of bacterial assemblages and physicochemical properties in surface sediments changed gradually from the Arctic continental shelf to deep-sea basin. Based on the results, bacterial biogeography in the Arctic seafloor sediments may be influenced by winnowing and re-deposition of surface sediments through the sediment gravity flow. The present study offers a deeper understanding of shelf convection and its role for the construction of bacterial assemblages in the Arctic Ocean.

The future of Arctic benthos: Expansion, invasion, and biodiversity

One of the logical predictions for a future Arctic characterized by warmer waters and reduced sea-ice is that new taxa will expand or invade Arctic seafloor habitats. Specific predictions regarding where this will occur and which taxa are most likely to become established or excluded are lacking, however. We synthesize recent studies and conduct new analyses in the context of climate forecasts and a paleontological perspective to make concrete predictions as to relevant mechanisms, regions, and functional traits contributing to future biodiversity changes. Historically, a warmer Arctic is more readily invaded or transited by boreal taxa than it is during cold periods. Oceanography of an ice-free Arctic Ocean, combined with life-history traits of invading taxa and availability of suitable habitat, determine expansion success. It is difficult to generalize as to which taxonomic groups or locations are likely to experience expansion, however, since species-specific, and perhaps population-specific autecologies, will determine success or failure. Several examples of expansion into the Arctic have been noted, and along with the results from the relatively few Arctic biological time-series suggest inflow shelves (Barents and Chukchi Seas), as well as West Greenland and the western Kara Sea, are most likely locations for expansion. Apparent temperature thresholds were identified for characteristic Arctic and boreal benthic fauna suggesting strong potential for range constrictions of Arctic, and expansions of boreal, fauna in the near future. Increasing human activities in the region could speed introductions of boreal fauna and reduce the value of a planktonic dispersal stage. Finally, shelf regions are likely to experience a greater impact, and also one with greater potential consequences, than the deep Arctic basin. Future research strategies should focus on monitoring as well as compiling basic physiological and life-history information of Arctic and boreal taxa, and integrate that with projections of human activities and likely ecosystem consequences to facilitate development of management strategies now and in the future.

A specific type of Fe-Mn mineralization on the Arctic seafloor

Three samples of Fe-Mn crusts overgrown on the surface of rocks are studied from the Mendeleev submarine rise located in the northern subpolar part of the Chukchi Sea. A massive crust up to 4–5 cm thick consists of an upper dense and lower denser layers similar in composition to the main one and contains 31–37% FeO and 11–13% MnO. Thin crusts and films are depleted in both components. Fe-vernadite is a major mineral of the crusts. The comparison of the major and trace element composition of the crusts with oceanic and marine nodules and hydrothermal crusts shows that they are mostly similar in composition to the nodules of the Bering Sea and are significantly distinct from the oceanic hydrothermal crusts. A small inclusion of the Pt-, Pd-, and Ru-rich (up to 1–2%) rock in one of the thin crusts points to the possible role of igneous rocks as a source of precious metals.

Evaluation of arctic multibeam sonar data quality using nadir crossover error analysis and compilation of a full-resolution data product

We document a new high-resolution multibeam bathymetry compilation for the Canada Basin and Chukchi Borderland in the Arctic Ocean – United States Arctic Multibeam Compilation (USAMBC Version 1.0). The compilation preserves the highest native resolution of the bathymetric data, allowing for more detailed interpretation of seafloor morphology than has been previously possible. The compilation was created from multibeam bathymetry data available through openly accessible government and academic repositories. Much of the new data was collected during dedicated mapping cruises in support of the United States effort to map extended continental shelf regions beyond the 200nm Exclusive Economic Zone. Data quality was evaluated using nadir-beam crossover-error statistics, making it possible to assess the precision of multibeam depth soundings collected from a wide range of vessels and sonar systems. Data were compiled into a single high-resolution grid through a vertical stacking method, preserving the highest quality data source in any specific grid cell. The crossover-error analysis and method of data compilation can be applied to other multi-source multibeam data sets, and is particularly useful for government agencies targeting extended continental shelf regions but with limited hydrographic capabilities. Both the gridded compilation and an easily distributed geospatial PDF map are freely available through the University of New Hampshire׳s Center for Coastal and Ocean Mapping (ccom.unh.edu/theme/law-sea). The geospatial pdf is a full resolution, small file-size product that supports interpretation of Arctic seafloor morphology without the need for specialized gridding/visualization software.

How much methane could be released from Arctic hydrates?

In Arctic seafloor sediments, methane, a potent greenhouse gas, is trapped in chemical structures called hydrates. Methane hydrates form at low‐temperature, high‐pressure conditions, and methane can be released if the temperature rises. Previous studies have raised concern that global climate change could lead to release of significant amounts of methane from Arctic hydrates.

Arctic sea-ice decline archived by multicentury annual-resolution record from crustose coralline algal proxy

Northern Hemisphere sea ice has been declining sharply over the past decades and 2012 exhibited the lowest Arctic summer sea-ice cover in historic times. Whereas ongoing changes are closely monitored through satellite observations, we have only limited data of past Arctic sea-ice cover derived from short historical records, indirect terrestrial proxies, and low-resolution marine sediment cores. A multicentury time series from extremely long-lived annual increment-forming crustose coralline algal buildups now provides the first high-resolution in situ marine proxy for sea-ice cover. Growth and Mg/Ca ratios of these Arctic-wide occurring calcified algae are sensitive to changes in both temperature and solar radiation. Growth sharply declines with increasing sea-ice blockage of light from the benthic algal habitat. The 646-y multisite record from the Canadian Arctic indicates that during the Little Ice Age, sea ice was extensive but highly variable on subdecadal time scales and coincided with an expansion of ice-dependent Thule/Labrador Inuit sea mammal hunters in the region. The past 150 y instead have been characterized by sea ice exhibiting multidecadal variability with a long-term decline distinctly steeper than at any time since the 14th century.

First Russian borehole on the Arctic seafloor

First Russian borehole on the Arctic seafloor

The International Bathymetric Chart of the Arctic Ocean (IBCAO) Version 3.0

The International Bathymetric Chart of the Arctic Ocean (IBCAO) released its first gridded bathymetric compilation in 1999. The IBCAO bathymetric portrayals have since supported a wide range of Arctic science activities, for example, by providing constraint for ocean circulation models and the means to define and formulate hypotheses about the geologic origin of Arctic undersea features. IBCAO Version 3.0 represents the largest improvement since 1999 taking advantage of new data sets collected by the circum‐Arctic nations, opportunistic data collected from fishing vessels, data acquired from US Navy submarines and from research ships of various nations. Built using an improved gridding algorithm, this new grid is on a 500 meter spacing, revealing much greater details of the Arctic seafloor than IBCAO Version 1.0 (2.5 km) and Version 2.0 (2.0 km). The area covered by multibeam surveys has increased from ∼6% in Version 2.0 to ∼11% in Version 3.0.

Material Talk: The Arctic Continental Shelf in the Law of the Sea Convention Discussion of the United States

Abstract The legal status of a large area of the Arctic seafloor is currently being redefined as the rapid melting of polar ice is enabling the exploitation and study of resource-rich underwater areas. The United Nations Convention on the Law of the Sea contains legal rules for establishing exploitation rights to the newly accessible seafloor. The United States has not joined the Law of the Sea Convention but may be legally entitled to areas of the Arctic seafloor, which has caused an upsurge of political discussion among U.S. political elites. In this article, I examine the process by which Arctic seafloor and ice come to influence policy discussion in the United States. I highlight the way in which material policy influence can be treated as historical rather than monocausal by using new materialist theory.

Results of the development of a long-range acoustic homing system for autonomous underwater vehicles

Modified international submarine engineering (ISE) explorer AUVs with an endurance of over 400 km are being used to aid in the mapping of the under-ice Arctic seafloor. The explorers are equipped with a DRDC-developed acoustic homing system built into the AUV nose cone. The acoustic receiver consists of seven digital hydrophones arranged in a tri-axis cross-dipole array. A controller/data processor located within the AUV pressure hull handles the real-time acoustic arrival azimuth and elevation estimation, as well as the control and calculations for an on-demand short-range three dimensional (3-D) localization system, and the control of vehicle telemetry data flow. The processor and array consume less than 2 W. A small, easily transportable, DRDC-designed acoustic transducer provides a powerful acoustic homing signal. Using the homing system, the vehicles were able to locate an acoustic beacon at a randomly drifting Ice Camp from a range in excess of 50 km (100-km ranges possible). The design, development...

Editorial - Arctic Ocean Diversity: synthesis

The most fundamental attributes of marine ecosystems are their Communities associated species composition, along with their specific abundances and biomass. Processoriented understanding of rates and interactions within ecosystems hinges on this first-order descriptive framework. While we know the major species and understand their roles in many parts of the world ocean, the fragmented nature of discrete studies has not fostered synthetic approaches. The societal need for such basic information has increased in recent decades as major facets of the human footprint are altering marine communities around the globe (i.e. climate change, species invasions, fisheries effects, oil and gas exploration, tourism). To understand such change, biodiversity studies spanning species inventories to functional linkages between diversity and ecosystems are necessary. Within this context, as well as driven by simple human curiosity, the International Census of Marine Life (CoML) was launched in 2000 (Yarincik and O’Dor 2005). CoML grew to a global network of researchers in more than 80 nations engaged in a 10-year scientific initiative to assess and explain the diversity, distribution, and abundance of life in the oceans. CoML addressed the fundamental questions “What lived in the oceans in the past, what lives in the oceans now, and what will live in the oceans in the future” (McIntyre 2010). The Arctic component of CoML, the Arctic Ocean Diversity project (ArcOD), was launched in 2004 (Gradinger et al. 2010), with a sister project launched in the Antarctic shortly thereafter (Schiaparelli and Hopcroft 2011). Globally, gaps in biodiversity knowledge are greatest in areas where the logistics limit access. In this regard, the Arctic is understudied due the challenges of sampling in remote icecovered waters. There is increased urgency to fill these gaps because climate change effects are strongly expressed in the Arctic, as apparent from the rapid loss of its sea ice over the past decades. The ArcOD umbrella sought to inventory biodiversity in the Arctic sea ice, water column and sea floor (Fig. 1)—from the shallow shelves to the deep basins—using a three-level approach: compilation of existing data, taxonomic identification of existing samples, and new collections focusing on taxonomic and regional gaps. While ArcOD was initiated mainly by US-based and Russian scientists, over 100 scientists in a dozen nations have contributed to ArcODrelated efforts, including many conducted during the International Polar Year 2007–9. In October 2010, the Census reported ‘A decade of discovery’ across regions and realms at the Royal Society in London. This present special issue presents a core contribution of ArcOD’s synthesis and contains pieces originally presented in their preliminary form at the Arctic Frontiers meeting in January 2010 in Tromso, Norway in the ‘Marine Biodiversity under Change’ session. The articles in this and the subsequent issue (Hop et al. 2011) have a strong focus on biodiversity, on a species, community and/or habitat level. Articles in this issue are pan-Arctic in spatial coverage with international author teams from ten countries and more than 25 institutions contributing the required expertise and majority of the data. The contributions in this issue are arranged in taxonomic order and span from microbes to marine mammals. Most contain new synthetic numerical analyses, as well as reviews of current knowledge, contemporary perspectives, and several presently expected This article belongs to the special issue “Arctic Ocean Diversity Synthesis”

Arctic Ocean gravity field derived from ICESat and ERS‐2 altimetry: Tectonic implications

A new, detailed marine gravity field for the persistently ice‐covered Arctic Ocean, derived entirely from satellite data, reveals important new tectonic features in both the Amerasian and Eurasian basins. Reprocessed Geoscience Laser Altimeter System (GLAS) data collected by NASA's Ice Cloud and land Elevation Satellite (ICESat) between 2003 and 2005 have been combined with 8 years worth of retracked radar altimeter data from ESA's ERS‐2 satellite to produce the highest available resolution gravity mapping of the entire Arctic Ocean complete to 86°N. This ARCtic Satellite‐only (ARCS) marine gravity field uniformly and confidently resolves marine gravity to wavelengths as short as 35 km. ARCS relies on a Gravity Recovery and Climate Experiment (GRACE)‐only satellite gravity model at long (>580 km) wavelengths and plainly shows tectonic fabric and numerous details imprinted in the Arctic seafloor, in particular, in the enigmatic Amerasian Basin (AB). For example, in the Makarov Basin portion of the AB, two north‐south trending lineations are likely clues to the highly uncertain seafloor spreading history which formed the AB.

Origin of pingo‐like features on the Beaufort Sea shelf and their possible relationship to decomposing methane gas hydrates

The Arctic shelf is currently undergoing dramatic thermal changes caused by the continued warming associated with Holocene sea level rise. During this transgression, comparatively warm waters have flooded over cold permafrost areas of the Arctic Shelf. A thermal pulse of more than 10°C is still propagating down into the submerged sediment and may be decomposing gas hydrate as well as permafrost. A search for gas venting on the Arctic seafloor focused on pingo‐like‐features (PLFs) on the Beaufort Sea Shelf because they may be a direct consequence of gas hydrate decomposition at depth. Vibracores collected from eight PLFs had systematically elevated methane concentrations. ROV observations revealed streams of methane‐rich gas bubbles coming from the crests of PLFs. We offer a scenario of how PLFs may be growing offshore as a result of gas pressure associated with gas hydrate decomposition.

Icebreaker expedition collects key Arctic seafloor and ice data

The recently completed Healy‐Oden Trans‐Arctic Expedition 2005 (HOTRAX′05) retrieved 29 piston cores averaging nearly 12 meters in length from a complete transect across the central Arctic Ocean (Figure 1). These cores provide a critically‐needed sample cache for both a pan‐Arctic stratigraphy and a long‐awaited paleoclimate record that it is hoped will greatly improve the understanding of how deepwater is exchanged between Arctic basins, how the climate system in the Arctic works over longer time intervals, and how the Arctic system interacts with global systems. The coring was done from the U.S. Coast Guard Cutter (USCGC) Healy, while oceanographic measurements were made from the Swedish icebreaker Oden.In addition to coring and oceanography, HOTRAX mapped the seafloor with multibeam bathymetry and collected chirp sonar profiles that not only mapped the strata to a sub‐bottom depth of 50–100 meters, but also provided detailed information on the geologic context of the core sites.

Expedition to the Volcanoes of the Arctic Seafloor

The AMORE Expedition headed for the so-called “Gakkel Ridge” where, on the floor of the Arctic Ocean, there is hot work afoot — for this ocean ridge is composed of active volcanoes

Arctic Ocean Gravity Field Derived From ERS-1 Satellite Altimetry

The derivation of a marine gravity field from satellite altimetry over permanently ice-covered regions of the Arctic Ocean provides much new geophysical information about the structure and development of the Arctic sea floor. The Arctic Ocean, because of its remote location and perpetual ice cover, remains from a tectonic point of view the most poorly understood ocean basin on Earth. A gravity field has been derived with data from the ERS-1 radar altimeter, including permanently ice-covered regions. The gravity field described here clearly delineates sections of the Arctic Basin margin along with the tips of the Lomonosov and Arctic mid-ocean ridges. Several important tectonic features of the Amerasia Basin are clearly expressed in this gravity field. These include the Mendeleev Ridge; the Northwind Ridge; details of the Chukchi Borderland; and a north-south trending, linear feature in the middle of the Canada Basin that apparently represents an extinct spreading center that "died" in the Mesozoic. Some tectonic models of the Canada Basin have proposed such a failed spreading center, but its actual existence and location were heretofore unknown.

Origin of sediment pellets from the Arctic seafloor: sea ice or icebergs?

Sediment cores from the Norwegian and Greenland Seas and the Nansen Basin were studied to determine the origin of sediment pellets, centimetre-sized aggregations of clay to sandsized sediment occurring in the cores. By comparing the grain size, grain shape and composition of the pellet sediments to sediments collected directly from the surfaces of sea ice in the Nansen Basin and from icebergs in the Barents Sea, the pelleted sediment was found to be more similar to that in the icebergs than that on the sea ice. The pellets may be formed on, in or under a glacier or during transport on/in an iceberg. When icebergs overturn or melt, the pellets fall out and are consolidated enough to survive a drop of up to 4 km to the ocean bottom and to retain their integrity even after burial on the seafloor.

Properties and history of the central eastern Arctic sea floor

ABSTRACTThe deep eastern Arctic basin between the Lomonosov Ridge and the Eurasian continental margin differs from other ocean basins in the very slow spreading of its floor and unusual depositional environment under perennial sea-ice cover. The recent expedition ARK IV/3 of RV Polar stern for the first time made geoscientific investigations from the northern margin of the Barents Sea north to the Nansen-Gakkel Ridge. Much deeper than most other mid-ocean ridges, this ridge is poorly-surveyed, but has a central valley which in places is deeper than 5.5 km, 1–1.5 km below the basin floors on either side. Heat flow in the central part of the valley is very rapid; both basement rocks and overlying sediments showed unexpectedly the influence of intense and long-term hydrothermal activity. The sediments on the northern and southern flanks of the ridge are slightly calcareous pelagic mud layers alternating with carbonate-free horizons, where up to 40% of the sedimentary section is soft mud clasts. Similar mud aggregates were observed on the surface of the multi-year sea ice, appearing to represent a special type of sediment transport by sea ice in the Transpolar Drift. In contrast to the western Arctic, Fram Strait and the Norwegian-Greenland Sea, gravel is rarely found in sediment cores. Recovered cores indicate that icebergs and sea ice carrying coarse sediment seldom rafted detritus to the study area during the last approximately 300,000 years.

Maps of the Arctic Basin Sea Floor. Part II: Bathymetry and Gravity of the Alpha Ridge: The 1983 CESAR Expedition

The general scarcity of geophysical data in the Arctic Ocean Basin and the lack of knowledge about the evolution of the Amerasia Basin and of the nature and origin of the Alpha Ridge led, in 1983, to the undertaking of a multidisciplinary polar expedition, code-named CESAR 83 for Canadian Expedition to Study the Alpha Ridge. The expedition was supported by the Canadian Armed Forces, first by parachuting 18 airborne engineers onto the CESAR site to build a 1.6 km long airstrip on the pack ice, and then by deploying and two months later evacuating the expedition by military Hercules aircraft. .... One of the major CESAR accomplishments was a regional bathymetric and gravity survey over the Ellesmere Island continental shelf and eastern part of the Alpha Ridge. Using the CESAR data as well as all publicly available data collected over the past 35 years, 100 contour interval bathymetric maps and 5 mGal contour intervale gravity free-air anomaly maps were compiled. These extend from the Ellesmere Island coast to the 116 degrees W meridian. The sea floor maps depict the Alpha Ridge as a very broad mountain complex of rugged topography with ridges and valleys trending parallel to the ridge axis. ... Elliptically shaped positive anomalies centered over the continental shelf break suggest that the continental margin adjacent to the Alpha Ridge has the typical Atlantic-type structure characteristic of the rest of the North American polar margin. Preliminary interpretation of the gravity field indicates that the Alpha Ridge crust is composed of very thick rocks of laterally uniform density and composition. It is suggested that the eastern part of the Alpha Ridge may be a massive accumulation of mafic rocks of probable oceanic origin formed by volcanic activity. This article is identified as Part II of a series on Maps of the Arctic Basin Sea Floor and is preceded by a A History of Bathymetry and its Interpretation (Webster, 1983). Key words: CESAR 83 expedition, Alpha Ridge, bathymetry, gravity, sea ice SLAR imagery