Fjord Research Articles

Influence of glacial turbidity and climate on diatom communities in two Fjord Lakes (British Columbia, Canada)

Inputs of glacial meltwater and changes in climate can profoundly influence lake ecosystems. Anderson and Seton lakes, two morphologically and chemically similar fjord lakes within the Fraser River Basin, British Columbia, experience a common biogeoclimatic setting, yet contrasting turbid-water influences from a hydroelectric development which diverts glacially-turbid water into Seton Lake, but not Anderson Lake. We conducted a comparative paleolimnological study of these two lakes to infer climatic and hydro-system influences affecting the freshwater algal community over the past ~ 200 years. Paleolimnological analysis of multiple cores for sedimentary diatom assemblages from Seton Lake revealed substantial diversion-related reductions in diatom concentrations and fluxes following the completion of the Bridge River Diversion (ca. 1950). Diatom compositional changes in Seton Lake were consistent with decreased light penetration due to increased turbidity. These changes did not occur in Anderson Lake, indicating the changes in the Seton Lake cores were likely driven by inflow of the glacially-turbid waters. Both lakes exhibited diatom compositional changes ca. 1980, with a rise in Lindavia comensis coincident with significant increases in local mean annual air temperatures and presumably associated limnological changes. Modern phytoplankton data, collected as part of this study, provides support for the occurrence of different L. comensis morphs throughout the sampling period (May–October) in Anderson Lake and in the fall in Seton Lake. The rise of L. comensis in both Anderson and Seton lakes is conceivably linked to the recent ice-free conditions enabling this taxon to persist throughout the year.

Rapid retreat of a Scandinavian marine outlet glacier in response to warming at the last glacial termination

Marine outlet glaciers on Greenland are retreating, yet it is unclear if the recent fast retreat will persist, and how atmosphere and ocean warming will impact future retreat. We show how a marine outlet glacier in Hardangerfjorden retreated rapidly in response to the abrupt warming following the Younger Dryas cold period (approximately 11,600 years before present). This almost 1000 m deep fjord, with several sills at 300–500 m depth, hosted a 175 km long outlet glacier at the western rim of the Scandinavian Ice Sheet. We use a dynamic ice-flow model constrained by well-dated terminal and lateral moraines to simulate the reconstructed 500-year retreat of Hardangerfjorden glacier. The model includes an idealized oceanic and atmospheric forcing based on reconstructions, but excludes the surface mass balance-elevation feedback. Our simulations show a highly episodic retreat driven by surface melt and warming fjord waters, paced by the fjord bathymetry. Warming air and ocean temperatures by 4–5 °C during the period of retreat result in a 125-km retreat of Hardangerfjorden glacier in 500 years. Retreat rates throughout the deglaciation vary by an order of magnitude from 50 to 2500 m a−1, generally close to 200 m a−1, punctuated by brief events of swift retreat exceeding 500 m a−1, each event lasting a few decades. We show that the fastest retreat rates occur in regions of the bed with the largest retrograde slopes; ice shelf length and fjord water depth is less important. Our results have implications for modern glacial fjord settings similar to Hardangerfjorden, where high retreat rates have been observed. Our findings imply that increasing air temperatures and warming subsurface waters in Greenland fjords will continue to drive extensive retreat of marine outlet glaciers. However, the recent high retreat rates are not expected to be sustained for longer than a few decades due to constraints by the fjord bathymetry.

Iron Supply by Subglacial Discharge Into a Fjord Near the Front of a Marine‐Terminating Glacier in Northwestern Greenland

AbstractGlacial fjords in Greenland show high productivity owing to the runoff of meltwater from the glaciers. Macronutrient dynamics (of nitrate, phosphate, and silicate) associated with subglacial discharge plumes in front of marine‐terminating glaciers are widely cited as important drivers of summer phytoplankton blooms in the fjords. However, the dynamics of iron (Fe), an essential micronutrient for primary production, remain largely unstudied in glacial fjords. To investigate the role of subglacial discharge plumes in Fe supply processes in glacial fjords, a comprehensive survey of Bowdoin Fjord, adjacent to the marine‐terminating Bowdoin Glacier in northwestern Greenland, was conducted. The subglacial discharge of Fe‐rich meltwater induces a buoyancy‐driven upwelling plume in front of the glacier that entrains nutrient‐rich Arctic‐ and Atlantic‐origin waters. The plume water potentially carried 4.5–8.7 × 107 g day−1 of total dissolvable Fe out of Bowdoin Fjord in summer. The concentration of dissolved Fe (dFe) in the plume water (~15.6 nmol kg−1) was 4 times higher than that in the water in the outer part of the fjord (~3.8 nmol kg−1). The dFe:nitrate + nitrite ratio (mmol mol−1) in the plume water varied between 0.58 and 3.2, several orders of magnitude higher than the phytoplankton cellular Fe:nitrate ratio estimated using the hypothetical Fe:C ratio and observed particulate organic carbon:nitrate ratio of the fjord. Hence, the plume water is replete with Fe with respect to phytoplankton demands. Subglacial discharge drives the upwelling of Fe and macronutrients toward the euphotic zone, which is vital for the generation of summer phytoplankton growth in glacial fjords.

Spatial genetic structure in Themisto libellula (Amphipoda: Hyperiidae) from the coastal Gulf of Alaska, Bering and Chukchi seas

Arctic marine ecosystems are undergoing rapid biogeographic responses to climate changes following the highest warming rates observed around the globe in recent decades. These drastic changes undoubtfully affect gene flow and genetic structure in the polar and subpolar regions. Here, we examine the genetic structure of the cold-water holozooplankton hyperiid Themisto libellula (Amphipoda: Hyperiidae), a key species in the Arctic ecosystem, using molecular population genetic approach. For the first time, we examine and compare populations across the Arcto-Pacific sector of the species biographical range from the northern Gulf of Alaska through the northern Chukchi Sea. We hypothesized that the complex history of the North Pacific and Amerasian Arctic marked by periodic intermissions and restrictions of the dominant northward flow resulted in vicariant differentiation of T. libellula along the latitudinal gradient. Mitochondrial and Rad-sequencing analyses revealed little genetic differentiation between closely connected Arctic populations in the Arctic Chukchi and Bering seas. In contrast, population from sub-Arctic glacial fjords in the Gulf of Alaska were distinct with few shared COI haplotypes. Strong FST estimates (FST = 0.16) based on 5197 neutral SNPs between the Gulf of Alaska and Bering Sea populations indicated very limited exchanges despite an existing connection between the areas via the Alaska Coastal Current. Our results suggest strong opportunities for genetic differentiation among marine zooplankton populations along the Pacific Alaskan coast and from the Arctic marginal seas.

New sponge species from Seno Magdalena, Puyuhuapi Fjord and Jacaf Canal (Chile)

Until now, only 177 species of sponges (Porifera) have been reported for Chilean coastal waters. Here we describe recent scuba diving surveys undertaken to improve our knowledge of the diversity of the sponge fauna of the Seno Magdalena, Puyuhuapi Fjord and Jacaf Canal in Chilean Patagonia. Despite these relatively harsh environments, our study yielded 23 species of Demospongiae, nine of which are new to science and described here: Hymerabdia imperfecta Bertolino, Costa & Pansini sp. nov., Axinella cylindrica Bertolino, Costa & Pansini sp. nov., Axinella coronata Bertolino, Costa & Pansini sp. nov., Biemna aurantiaca Bertolino, Costa & Pansini sp. nov., Biemna erecta Bertolino, Costa & Pansini sp. nov., Biemna typica Bertolino, Costa & Pansini sp. nov., Scopalina cribrosa Bertolino, Costa & Pansini sp. nov., Rhizaxinella strongylata Bertolino, Costa & Pansini sp. nov. and Darwinella pronzatoi Bertolino, Costa & Pansini sp. nov. One species, Hymedesmia (Stylopus) lissostyla (Bergquist & Fromont, 1988), is reported for the first time for Chile.

Understanding Regional and Seasonal Variability Is Key to Gaining a Pan-Arctic Perspective on Arctic Ocean Freshening

The Arctic marine system is large and heterogeneous, harsh and remote, and now changing very rapidly, all of which contribute to our current inadequate understanding of its basic structures and functions. In particular, many key processes within and external to the Arctic Ocean are intrinsically linked to its freshwater system, which itself is undergoing rapid and uncertain change. The role of the freshwater system (delivery, disposition, storage, and export) in the Arctic Ocean has recently received significant attention; however, due to the fact that few studies are able to cover all regions and seasons of the Arctic Ocean equally, we still lack an accessible, unified pan-Arctic representation generalizing the impacts of freshwater on the upper Arctic Ocean where many biological and geochemical interactions occur. This work seeks to distill our current understanding of the Arctic freshwater system and its impacts into conceptual diagrams which we use as a basis to speculate on the impact of future changes. We conclude that inclusion of regional and seasonal variability is required in order to gain a pan-Arctic perspective on the physical-geochemical-biological state of the upper Arctic Ocean. As an example of regionality, enhanced stratification due to freshening will be more important in the Pacific influenced Amerasian Basin, which stores the bulk of the freshwater burden, while the Atlantic influenced Eurasian Basin will experience more consequences from increases in incoming heat. River influenced coastal regions will experience a mosaic of these and other biogeochemical effects, whereas glacial fjords may follow their own unique trajectories due to the loss of upwelling mechanisms at glacial fronts. As an example of seasonality, the continued modulation of the sea ice freeze-melt cycle has increased the seasonal freshwater burden in the deep basins dramatically as the system progresses towards ice-free summer conditions, but will eventually reverse, reducing the seasonal flux of freshwater by more than half in a future, perennially ice-free ocean. It is our goal that these conceptualizations based on the current state-of-the-art will drive hypothesis-based research to investigate the physical-biogeochemical response to a changing freshwater cycle in a future Arctic Ocean with greatly reduced ice cover.

Meltwater‐Enhanced Nutrient Export From Greenland's Glacial Fjords: A Sensitivity Analysis

AbstractAs mass loss from the Greenland Ice Sheet accelerates, this modeling study considers how meltwater inputs to the ocean can impact marine ecosystems using a simplified fjord scenario. At marine‐terminating glaciers in Greenland fjords, meltwater can be delivered far below the sea surface, both as subglacial runoff (from atmosphere‐driven surface melt) and as basal melt (from ocean heat). Such delivery can result in buoyancy‐driven upwelling and the upward entrainment of nutrient‐rich deep water, which can support phytoplankton growth in fjord surface waters. For this study, we use an idealized fjord‐scale model to investigate which properties of glaciers and fjords govern the transport of buoyantly upwelled nutrients from fjords. We model the influence of fjord geometry, hydrology, wind, tides, and phytoplankton growth within the fjord on meltwater‐driven nutrient export to the ocean. We use the Regional Ocean Modeling System (ROMS) coupled to a buoyant plume model and a biogeochemical model to simulate physical and biogeochemical processes within an idealized tidewater glacial fjord. Results show that meltwater‐driven nutrient export increases with larger subglacial discharge rates and deeper grounding lines, features that are both likely to change with continued ice sheet melting. Nutrient export decreases with longer residence times, allowing greater biological drawdown. While the absence of a coastal current in the model setup prevents the downstream advection of exported nutrients, results suggest that shelf‐forced flows could influence nutrient residence time within fjords. This simplified model highlights key uncertainties requiring further observation to understand ecological impacts of Greenland mass loss.

Soundscape of a Narwhal Summering Ground in a Glacier Fjord (Inglefield Bredning, Greenland)

AbstractNarwhal acoustic phonation is embedded in the icy cacophony of one of the noisiest soundscapes in the ocean. The high susceptibility of the narwhal to climate change highlights the need for further efforts to document baseline descriptions of the sounds it produces, especially given the potential anthropogenic impacts on their habitats. However, observations are rare, and narwhal acoustic behavior and habitats are poorly understood (attributed to both the skittish nature of hard‐to‐approach narwhals and the difficult access to remote and often dangerous glacier fjords). Here, we provide acoustic measurements in a narwhal summering ground in glacial fjords in Northwest Greenland that were mainly collected during Inuit hunting expeditions. This unique observational strategy near a key narwhal hot spot allowed the acquisition of supervised near‐source recordings of narwhal vocalizations, which confirms the animal's presence within several hundred meters of an actively calving Bowdoin Glacier. We accurately describe the acoustic signals and noise related to the cetacean, environmental, and anthropogenic sources, show previously unreported signals and their properties, report elevated background noise levels near the calving front, and discuss the general soundscape features of a glacier fjord. The baseline information presented here should encourage long‐term follow‐up acoustic monitoring in the area and provides an important reference for comparisons with future conditions and other regions. We also anticipate that our work will be a starting point both for the development of criteria to distinguish pulsed calls from terminal buzzes and for a thorough discussion of the dual use of passive acoustic monitoring in traditional hunting practices.

Postglacial evolution of marine and lacustrine water bodies in Bunger Hills

AbstractUnglaciated coastal areas in East Antarctica provide records of past ice sheet and glacier fluctuations and subsequent environmental conditions. In this paper we review lithological, geochemical, diatom and radiocarbon data from sediment records from inland and epishelf lakes in Bunger Hills, East Antarctica. While some hilltops were unglaciated during the Last Glacial Maximum, till deposits in lake basins indicate infilling by glacier ice prior to the Holocene. Proglacial sedimentation occurred in lakes during the early Holocene. Around 9.6 kabp, deposition of marine sapropel started under relatively warm climate conditions. Inland lakes were affected by high clastic input from meltwater runoff untilc.7.9 kabp, when deposition became highly organic and biogenic proxies indicate a period of cooler conditions. Epishelf lakes experienced a decrease in water exchange with the ocean and increased freshwater input around 7.7 ± 0.2 kabpand after 2.2 kabp. This probably resulted from grounding line advances of the bounding glaciers, which could be either controlled by relative sea level (RSL) lowering and/or climate-driven glacier dynamics. The absence of marine sediments in the postglacial record of Algae Lake indicates that Holocene RSL probably reached a maximum at or below 10 m above present sea level.

Contrasting assemblages of seabirds in the subglacial meltwater plume and oceanic water of Bowdoin Fjord, northwestern Greenland

AbstractIn Greenland, tidewater glaciers discharge turbid subglacial freshwater into fjords, forming plumes near the calving fronts, and these areas serve as an important foraging habitat for seabirds. To investigate the effect of subglacial discharge on the foraging assemblages of surface feeders and divers in a glacial fjord, we conducted boat-based seabird surveys, near-surface zooplankton samplings, and hydrographic measurements at Bowdoin Fjord, northwestern Greenland in July. Foraging surface feeders (black-legged kittiwake Rissa tridactyla, glaucous gull Larus hyperboreus, and northern fulmar Fulmarus glacialis) aggregated within a plume-affected area in front of Bowdoin Glacier. This area was characterized by highly turbid subglacial meltwater and abundant large-sized zooplankton including Calanus hyperboreus, chaetognaths, and ctenophores near the surface. Surface feeders fed on these aggregated prey presumably transported to the surface by strong upwelling of subglacial meltwater. In contrast, divers (little auk Alle alle, thick-billed murre Uria lomvia, and black guillemot Cepphus grylle) foraged outside the fjord, where turbidity was low and jellyfish and Calanus copepods dominated under the influence of Atlantic water. Our study indicates spatial segregation between surface feeders and divers in a glacial fjord; surface feeders are not hindered by turbidity if taking prey at the surface, whereas divers need clear water.

Hydrography and energetics of a cold subpolar fjord: Andvord Bay, western Antarctic Peninsula

Fjords along the western Antarctic Peninsula contain rich marine ecosystems and tidewater glaciers potentially sensitive to ocean change, but much is unknown about the physical oceanography of these fjords. This paper presents a comprehensive description of the physical environment of Andvord Bay, a glacial fjord located in the Gerlache Strait on the northern end of the Peninsula. Measurements were collected as part of the FjordEco program between November 2015 and March 2017, including during three research cruises and from a number of fixed installations (sub-surface moorings, time lapse cameras, and automatic weather stations). Andvord Bay is located just north of a sill in the Gerlache Strait. This sill inhibits the direct influence of warm Upper Circumpolar Deep Water from the shelf, and deep waters in the fjord are therefore relatively cold. As a result, glaciers in Andvord Bay are not subject to the substantial ocean-driven retreat observed farther south on the Peninsula. Instead, mass flux from the glaciers occurs mainly through calving. The influence of meltwater in Andvord Bay is small compared to glacial fjords in the Arctic and in the South Shetland Islands, although summer freshening is evident in the fjord near-surface layer, likely as a result of glacial inputs. The combination of surface freshening and the absence of strong mean wind forcing in the fjord results in salinity stratification extending well into the euphotic zone, providing advantageous conditions for phytoplankton blooms. Andvord Bay is generally dynamically quiet compared to the ambient ocean, with the exception of during local katabatic wind events. Exchange with the Gerlache Strait is weak, although the deep waters of the fjord are replenished on an annual scale through slow lateral exchange with the outside. In addition, deep convection may play a role in ventilating subsurface waters in winter.

Phenotypic Plasticity or a Reproductive Dead End? Primnoa pacifica (Cnidaria: Alcyonacea) in the Southeastern Alaska Region

Red tree corals (Primnoa pacifica) are abundant in the eastern Gulf of Alaska, from the glacial fjords of Southeast Alaska where they emerge to as shallow as 6 m, to the continental shelf edge and seamounts where they are more commonly found at depths greater than 150 m. This keystone species forms large thickets, creating habitat for many associated species, including economically valuable fishes and crabs, and so are important benthic suspension feeders in this region. Though the reproductive periodicity over 1.5 year period was reported in 2014 from a shallow fjord (Tracy Arm), this study examined reproductive ecologies from 8 sites – two within Glacier Bay National Park and Preserve, three on the continental shelf edge, one within Endicott Arm (Holkham Bay) and two time points from the Tracy Arm (Holkham Bay) study. Male reproductive traits were similar at all sites but there were distinct differences in oogenesis. Though fecundity mostly showed no significant difference between sites, there was a trend of increasing number of eggs with depth. Indeed, the average oocyte sizes from Tracy Arm (the shallowest site) was 105 m, whereas from Shutter Ridge (one of the deepest sites) the average size was 309 m. Moreover, the maximum oocyte size at Tracy Arm was 802 m, whereas it was 2120 m at Dixon Entrance, an almost 3-fold difference, and one not usually observed within a single species. We propose two theories to explain the observed differences, a) this species shows great phenotypic plasticity in reproductive ecology, adjusting to different environmental variables based on energetic need and potentially demonstrating micro-evolution; or b) the fjord sites are at a reproductive dead end, with the stress of shallow water conditions effectively preventing gametogenesis reaching full potential and likely limiting successful reproductive events from occurring, at least on a regular basis.

Benthic Fauna of Oga Bay (Novaya Zemlya, Kara Sea)

The benthic fauna of Oga Bay (Kara Sea, Novaya Zemlya archipelago) was studied in 2015–2016 during the R/V Akademik Mstislav Keldysh expeditions. Five grab stations at depths of 70–140 m were sampled (three grabs per station). Three macrobenthic communities consecutively replacing each other from the inner near-glacier part of the bay toward the outer slope were revealed. Concentration of suspended matter in the water column and in the near-bottom layer, caused by powerful sedimentation from the Goluboi (Oga) glacier was the main factor determining the macrobenthic communities distribution. An overall decrease in abundance, biomass and diversity of macrofauna was found in the area of glacier discharge. The community dominated by bivalve Portlandia arctica inhabits the main part of the bay. The peculiarities of the benthic communities of the Arctic glacial bays and fjords are discussed.

Inter fjord variations as a key contributor in the meiobenthic faunal distribution in the Arctic Kongsfjord, Svalbard

The community pattern of meiobenthos in an inner and outer glacial fjord of Kongsfjord was analysed during this study. This study examined the hypothesis that there is a significant difference in the distribution of total meiofauna and the major meiofaunal groups between the inner and outer fjords and it also looked into the effect of environmental variables on their distribution. Meiofaunal abundance and diversity was higher in the inner fjord, indicating that meiofauna can be less sensitive to sediment disturbances caused by glacial activity. Average abundance and biomass of the major meiofaunal groups, namely nematodes (54%) and foraminiferans (37%) were higher in the outer region. 45 species of nematodes representing 20 families were identified during the study, in which Dorylaimopsis sp. (39.55%) and Terschellingia longicaudata (12.53%) had the highest relative abundance. Out of the 56 foraminiferan species belonging to 5 suborders, Nonionellina labradorica (18.30%) and Cassidulina teretis (8.85%) had the highest relative abundance. There are clear and significant changes (ANOSIM) in the assemblage of meiofauna with increasing distance from the glacial front which correlates to environmental variables. Species contributing to differences between inner and outer basins (SIMPER) were also determined. Among nematodes, Chromadorids and Araeolaimids had a tendency to distribute in the inner fjord while Enoplids and Monhysterids were more prevalent in the outer fjord. Sediment organic matter, silt content and pH were the best matching variables (BEST) for the distribution of both nematodes and foraminiferans. The Principal Component Analysis (PCA) revealed that environmental variations have significant patterns in the faunal distribution in Kongsfjord. From this study it can be inferred that the inner fjord has the maximum numerical abundance of meiofauna but the foraminiferans and nematodes were numerically abundant in the outer fjord and there is also significant difference in the distribution of species between the two fjords.

Seasonal Variations in Iceberg Freshwater Flux in Sermilik Fjord, Southeast Greenland From Sentinel‐2 Imagery

AbstractIceberg discharge is estimated to account for up to 50% of the freshwater flux delivered to glacial fjords. The amount, timing, and location of iceberg melting impacts fjord‐water circulation and heat budget, with implications for glacier dynamics, nutrient cycling, and fjord productivity. We use Sentinel‐2 imagery to examine seasonal variations in freshwater flux from open‐water icebergs in Sermilik Fjord, Greenland during summer and fall of 2017–2018. Using iceberg velocities derived from visual‐tracking and changes in total iceberg volume with distance down‐fjord from Helheim Glacier, we estimate maximum average two‐month full‐fjord iceberg‐derived freshwater fluxes of ~1,060 ± 615, 1,270 ± 735, 1,200 ± 700, 3,410 ± 1,975, and 1,150 ± 670 m3/s for May–June, June–July, July–August, August–September, and September–November, respectively. Fluxes decrease with distance down‐fjord, and on average, 86–91% of iceberg volume is lost before reaching the fjord mouth. This method provides a simple, invaluable tool for monitoring seasonal and interannual iceberg freshwater fluxes across a range of Greenlandic fjords.

Bathymetry of Northwest Greenland Using “Ocean Melting Greenland” (OMG) High-Resolution Airborne Gravity and Other Data

Marine-terminating glaciers dominate the evolution of the Greenland Ice Sheet (GrIS) and its contribution to sea-level rise. Widespread glacier acceleration has been linked to the warming of ocean waters around the periphery of Greenland but a lack of information on the bathymetry of the continental shelf and glacial fjords has limited our ability to understand how subsurface, warm, salty ocean waters of Atlantic origin (AW) reach the glaciers and melt them from below. Here, we employ high-resolution, airborne gravity data (AIRGrav) in combination with multibeam echo sounding (MBES) data, to infer the bathymetry of the coastal areas of Northwest Greenland for NASA’s Ocean Melting Greenland (OMG) mission. High-resolution, AIRGrav data acquired on a 2 km spacing, 150 m ground clearance, with 1.5 mGal crossover error, is inverted in three dimensions to map the bathymetry. To constrain the inversion away from MBES data, we compare two methods: one based on the Direct Current (DC) shift of the gravity field (absolute minus observed gravity) and another based on the density of the bedrock. We evaluate and compare the two methods in areas with complete MBES coverage. We find the lowest standard error in bed elevation (±60 m) using the DC shift method. When applied to the entire coast of Northwest Greenland, the three-dimensional inversion reveals a complex network of connected sea bed channels, not known previously, that provide natural and varied pathways for AW to reach the glaciers across the continental shelf. The study demonstrates that the gravity approach offers an efficient and practical alternative to extensive ship mapping in ice-filled waters to obtain information critical to understanding and modeling ice-ocean interaction along ice sheet margins.

Nutrient release to oceans from buoyancy-driven upwelling at Greenland tidewater glaciers

The discharge of nutrient-rich meltwater from the Greenland Ice Sheet has emerged as a potentially important contributor to regional marine primary production and nutrient cycling. While significant, this direct nutrient input by the ice sheet may be secondary to the upwelling of deep-ocean-sourced nutrients driven by the release of meltwater at depth in glacial fjords. Here, we present a comprehensive suite of micro- and macronutrient observations collected in Sermilik Fjord at the margin of Helheim, one of Greenland’s largest glaciers, and quantitatively decompose glacial and ocean contributions to fjord dissolved nutrient inventories. We show that the substantial enrichment in nitrate, phosphate and silicate observed in the upper 250 m of the glacial fjord is the result of upwelling of warm subtropical waters present at depth throughout the fjord. These nutrient-enriched fjord waters are subsequently exported subsurface to the continental shelf. The upwelled nutrient transport within Sermilik rivals exports by the largest Arctic rivers and the ice sheet as a whole, suggesting that glacier-induced pumping of deep nutrients may constitute a major source of macronutrients to the surrounding coastal ocean. The importance of this mechanism is likely to grow given projected increases in surface melt of the ice sheet. Glacial meltwater from the Greenland Ice Sheet causes buoyancy-driven upwelling of nutrient-rich, subtropical waters from depth to the continental shelf. This nutrient transport may exceed the direct ice sheet inputs, according to geochemical analyses of transect samples from Sermilik Fjord.

Export of Strongly Diluted Greenland Meltwater From a Major Glacial Fjord

AbstractThe Greenland Ice Sheet has been, and will continue, losing mass at an accelerating rate. The influence of this anomalous meltwater discharge on the regional and large‐scale ocean could be considerable but remains poorly understood. This uncertainty is in part a consequence of challenges in observing water mass transformation and meltwater spreading in coastal Greenland. Here we use tracer observations that enable unprecedented quantification of the export, mixing, and vertical distribution of meltwaters leaving one of Greenland's major glacial fjords. We find that the primarily subsurface meltwater input results in the upwelling of the deep fjord waters and an export of a meltwater/deepwater mixture that is 30 times larger than the initial meltwater release. Using these tracer data, the vertical structure of Greenland's summer meltwater export is defined for the first time showing that half the meltwater export occurs below 65 m.

Biodiversity patterns of rock encrusting fauna from the shallow sublittoral of the Admiralty Bay

The Antarctic sublittoral is one of the most demanding habitat for polar bottom-dwelling organisms, as the disturbance of this zone is highly intense. Rapid changes in the marine environment, such as increases in atmosphere and surface water temperatures, can cause dramatic changes in biodiversity, especially in glacial fjords affected by heavy melt water inputs from the retreating glaciers. In such areas, rocks are often an important support for local diversity, providing habitats for a number of encrusting organisms. Thus, understanding the patterns of diversity of shallow rock encrusting fauna and factors controlling it are particularly important.The structure and diversity patterns of rock encrusting fauna were examined from four ecologically contrasting sites in the shallow sublittoral (6–20 m) of Admiralty Bay (King George Island). The results revealed a rich and abundant encrusting community with bryozoans and polychaetes outcompeting representatives of other fauna such as foraminifera and porifera. Spatial variability in species composition, as well as biological parameters, revealed the trend of encrusting assemblages declining towards the inner fjord areas - strongly affected by high sediment input (species richness: 13.3 ± 1.2, and abundance: 68,932.99 ± 11,915.98 individuals m−2 ± standard error). In contrast, at sites more open to the central basin, a peak of biological parameters was observed (24.8 ± 1.4 and 297,360.9 ± 30,314.72, respectively). We suggest that increased sedimentation was the major factor structuring the encrusting assemblages in Ezcurra Inlet, masking the influence of other parameters, such as food and light availability, which are important for the distribution of epifauna. Thus, if the increasing intensity of glacial processes will continue in the upcoming years, the diversity of the encrusting fauna in the shallow sublittoral could dramatically decrease.

Vulnerability of Southeast Greenland Glaciers to Warm Atlantic Water From Operation IceBridge and Ocean Melting Greenland Data.

We employ National Aeronautics and Space Administration (NASA)'s Operation IceBridge high‐resolution airborne gravity from 2016, NASA's Ocean Melting Greenland bathymetry from 2015, ice thickness from Operation IceBridge from 2010 to 2015, and BedMachine v3 to analyze 20 major southeast Greenland glaciers. The results reveal glacial fjords several hundreds of meters deeper than previously thought; the full extent of the marine‐based portions of the glaciers; deep troughs enabling warm, salty Atlantic Water (AW) to reach the glacier fronts and melt them from below; and few shallow sills that limit the access of AW. The new oceanographic and topographic data help to fully resolve the complex pattern of historical ice front positions from the 1930s to 2017: glaciers exposed to AW and resting on retrograde beds have retreated rapidly, while glaciers perched on shallow sills or standing in colder waters or with major sills in the fjords have remained stable.