Characterising the sea ice environment using a newly developed sensor array mounted on an under-ice trawl

One of the most pronounced impacts of climate change is the changing sea ice cover, which has implications for sea ice-associated ecosystems that depend on carbon produced by ice-associated algae. In order to fully understand these ecosystems there is a need to understand both the physical and biological components. We present preliminary results from Polarstern cruises to the Eastern Central Arctic Ocean (summer 2012) and Weddell Sea (fall-winter 2013). Biological samples were acquired from the under-ice environment using the Surface and Under-Ice Trawl (SUIT) and from within the ice by extracting ice cores. Biophysical properties of sea ice and under-ice environments were characterized using a sensor array mounted on the SUIT that measured ice thickness, under-ice light spectra, water properties and chlorophyll a biomass (in- and under-ice). Modal ice thicknesses were between 0.45-1.38 m (Arctic) and 0.23-0.70 m (Weddell Sea). Sea ice properties were related to the distribution of some key under-ice species (e.g. Polar Cod and Antarctic Krill). Previous studies have used under-ice light spectra to derive ice-algal biomass but were limited to local-scale point measurements. We present a new method for calculating ice-algal biomass from under-ice spectra on local- to meso-scales and compare the results using both methods

Antarctic sympagic meiofauna in winter: Comparing diversity, abundance and biomass between perennially and seasonally ice-covered regions

This study of Antarctic sympagic meiofauna in pack ice during late winter compares communities between the perennially ice-covered western Weddell Sea and the seasonally ice-covered southern Indian Ocean. Sympagic meiofauna (proto- and metazoans >20 μm) and eggs >20 μm were studied in terms of diversity, abundance and carbon biomass, and with respect to vertical distribution. Metazoan meiofauna had significantly higher abundance and biomass in the western Weddell Sea (medians: 31.1×103 m−2 and 6.53mg m−2, respectively) than in the southern Indian Ocean (medians: 1.0×10 103 m−2and 0.06 mg m−2, respectively). Metazoan diversity was also significantly higher in the western Weddell Sea. Furthermore, the two regions differed significantly in terms of meiofauna community composition, as revealed through multivariate analyses. The overall diversity of sympagic meiofauna was high, and integrated abundance and biomass of total meiofauna were also high in both regions (0.6–178.6×103 m−2 and 0.02–89.70mg m−2, respectively), mostly exceeding values reported earlier from the western Weddell Sea in winter. We attribute the differences in meiofauna communities between the two regions to the older first-year ice and multi-year ice that is present in the western Weddell Sea, but not in the southern Indian Ocean. Our study indicates the significance of perennially ice-covered regions for the establishment of diverse and abundant meiofauna communities. Furthermore, it highlights the potential importance of sympagic meiofauna for the organic matter pool and trophic interactions in sea ice

Spatial variability in sea-ice algal biomass: an under-ice remote sensing perspective

Sea-ice algae are a paramount feature of polar marine ecosystems and ice algal standing stocks are characterized by a high spatio-temporal variability. Traditional sampling techniques, e.g., ice coring, are labor intensive, spatially limited and invasive, thereby limiting our understanding of ice algal biomass variability patterns. This has consequences for quantifying ice-associated algal biomass distribution, primary production, and detecting responses to changing environmental conditions. Close-range under-ice optical remote sensing techniques have emerged as a capable alternative providing non-invasive estimates of ice algal biomass and its spatial variability. In this review we first summarize observational studies, using both classical and new methods that aim to capture biomass variability at multiple spatial scales and identify the environmental drivers. We introduce the complex multi-disciplinary nature of under-ice spectral radiation profiling techniques and discuss relevant concepts of sea-ice radiative transfer and bio-optics. In addition, we tabulate and discuss advances and limitations of different statistical approaches used to correlate biomass and under-ice light spectral composition. We also explore theoretical and technical aspects of using Unmanned Underwater Vehicles (UUV), and Hyperspectral Imaging (HI) technology in an under-ice remote sensing context. The review concludes with an outlook and way forward to combine platforms and optical sensors to quantify ice algal spatial variability and establish relationships with its environmental drivers

Sea ice CO2 flux in the Southern Ocean during mid-winter and early spring

第4回極域科学シンポジウム個別セッション：[OB] 生物圏11月12日（火）13:00-14:00　国立国語研究所 ２階ラウン

SIPEX-2: A study of sea-ice physical, biochemical and ecosystem processes off East Antarctica during spring 2012

This editorial introduces a suite of articles resulting from the second Sea Ice Physics and Ecosystems eXperiment(SIPEX-2) voyage by presenting some background information on the study areaandAntarcticsea-ice conditions,and summarising the key findings from the project.Using the Australian iceb reaker RV Aurora Australis, SIPEX-2 was conducted in the area between 115–125°E and 62–66°S off East Antarctica during September to November 2012. This region had been sampled during two previous experiments,i.e. ARISE in 2003 (Massom etal.,2006a) and SIPEX in 2007(Worbyetal.,2011a). The 2012 voyage combined traditional and newly developed sampling methods with satellite and other data to measure sea-ice physical properties and pro- cesses on large scales,which provided context for bio geochemical and ecological case studies. Thes pecific goals of the SIPEX-2 project were to:(i)measure the spatial variability in sea-ice and snow-cover properties over small-to regional-length scales;(ii) improve understanding of sea-ice kinematic processes;and(iii) advance knowledge of the links between sea-ice physical characteristics,sea-ice biogeochemical cycling and ice-associated food-web dynamics.Our field-based activities were designed to inform modelling approaches and to improve our capability to assess impacts of predicted changes in Antarctic sea ice on Southern Ocean biogeochemical cycles and ecosystem function

Microalgal community structure and primary production in Arctic and Antarctic sea ice : A synthesis

Sea ice is one the largest biomes on earth, yet it is poorly described by biogeochemical and climate models. In this paper, published and unpublished data on sympagic (ice-associated) algal biodiversity and productivity have been compiled from more than 300 sea-ice cores and organized into a systematic framework. Significant patterns in microalgal community structure emerged from this framework. Autotrophic flagellates characterize surface communities, interior communities consist of mixed microalgal populations and pennate diatoms dominate bottom communities. There is overlap between landfast and pack-ice communities, which supports the hypothesis that sympagic microalgae originate from the pelagic environment. Distribution in the Arctic is sometimes quite different compared to the Antarctic. This difference may be related to the time of sampling or lack of dedicated studies. Seasonality has a significant impact on species distribution, with a potentially greater role for flagellates and centric diatoms in early spring. The role of sea-ice algae in seeding pelagic blooms remains uncertain. Photosynthesis in sea ice is mainly controlled by environmental factors on a small scale and therefore cannot be linked to specific ice types. Overall, sea-ice communities show a high capacity for photoacclimation but low maximum productivity compared to pelagic phytoplankton. Low carbon assimilation rates probably result from adaptation to extreme conditions of reduced light and temperature in winter. We hypothesize that in the near future, bottom communities will develop earlier in the season and develop more biomass over a shorter period of time as light penetration increases due to the thinning of sea ice. The Arctic is already witnessing changes. The shift forward in time of the algal bloom can result in a mismatch in trophic relations, but the biogeochemical consequences are still hard to predict. With this paper we provide a number of parameters required to improve the reliability of sea-ice biogeochemical models.Peer reviewe

Iron biogeochemistry in Antarctic pack ice during SIPEX-2

Our study quantified the spatial and temporal distribution of Fe and ancillary biogeochemical parameters at six stations visited during an interdisciplinary Australian Antarctic marine science voyage (SIPEX-2) within the East Antarctic first-year pack ice zone during September–October 2012. Unlike previous studies in the area, the sea ice Chlorophyll a, Particulate Organic Carbon and Nitrogen (POC and PON) maxima did not occur at the ice/water interface because of the snow loading and dynamic processes under which the sea ice formed. Iron in sea ice ranged from 0.9 to 17.4 nM for the dissolved (<0.2 µm) fraction and 0.04 to 990 nM for the particulate (>0.2 µm) fraction. Our results highlight that the concentration of particulate Fe in sea ice was highest when approaching the continent. The high POC concentration and high particulate iron to aluminium ratio in sea ice samples demonstrate that 71% of the particulate Fe was biogenic in composition. Our estimated Fe flux from melting pack ice to East Antarctic surface waters over a 30 day melting period was 0.2 µmol/m2/d of DFe, 2.7 µmol/m2/d of biogenic PFe and 1.3 µmol/m2/d of lithogenic PFe. These estimates suggest that the fertilization potential of the particulate fraction of Fe may have been previously underestimated due to the assumption that it is primarily lithogenic in composition. Our new measurements and calculated fluxes indicate that a large fraction of the total Fe pool within sea ice may be bioavailable and therefore, effective in promoting primary productivity in the marginal ice zone

Methods for biogeochemical studies of sea ice: The state of the art, caveats, and recommendations

Over the past two decades, with recognition that the ocean’s sea-ice cover is neither insensitive to climate change nor a barrier to light and matter, research in sea-ice biogeochemistry has accelerated significantly, bringing together a multi-disciplinary community from a variety of fields. This disciplinary diversity has contributed a wide range of methodological techniques and approaches to sea-ice studies, complicating comparisons of the results and the development of conceptual and numerical models to describe the important biogeochemical processes occurring in sea ice. Almost all chemical elements, compounds, and biogeochemical processes relevant to Earth system science are measured in sea ice, with published methods available for determining biomass, pigments, net community production, primary production, bacterial activity, macronutrients, numerous natural and anthropogenic organic compounds, trace elements, reactive and inert gases, sulfur species, the carbon dioxide system parameters, stable isotopes, and water-ice-atmosphere fluxes of gases, liquids, and solids. For most of these measurements, multiple sampling and processing techniques are available, but to date there has been little intercomparison or intercalibration between methods. In addition, researchers collect different types of ancillary data and document their samples differently, further confounding comparisons between studies. These problems are compounded by the heterogeneity of sea ice, in which even adjacent cores can have dramatically different biogeochemical compositions. We recommend that, in future investigations, researchers design their programs based on nested sampling patterns, collect a core suite of ancillary measurements, and employ a standard approach for sample identification and documentation. In addition, intercalibration exercises are most critically needed for measurements of biomass, primary production, nutrients, dissolved and particulate organic matter (including exopolymers), the CO2 system, air-ice gas fluxes, and aerosol production. We also encourage the development of in situ probes robust enough for long-term deployment in sea ice, particularly for biological parameters, the CO2 system, and other gases

Antarctic ecosystems in transition – life between stresses and opportunities

Important findings from the second decade of the 21st century on the impact of environmental change on biological processes in the Antarctic were synthesised by 26 international experts. Ten key messages emerged that have stakeholder-relevance and/or a high impact for the scientific community. They address (i) altered biogeochemical cycles, (ii) ocean acidification, (iii) climate change hotspots, (iv) unexpected dynamism in seabed-dwelling populations, (v) spatial range shifts, (vi) adaptation and thermal resilience, (vii) sea ice related biological fluctuations, (viii) pollution, (ix) endangered terrestrial endemism and (x) the discovery of unknown habitats. Most Antarctic biotas are exposed to multiple stresses and considered vulnerable to environmental change due to narrow tolerance ranges, rapid change, projected circumpolar impacts, low potential for timely genetic adaptation, and migration barriers. Important ecosystem functions, such as primary production and energy transfer between trophic levels, have already changed, and biodiversity patterns have shifted. A confidence assessment of the degree of 'scientific understanding' revealed an intermediate level for most of the more detailed sub-messages, indicating that process-oriented research has been successful in the past decade. Additional efforts are necessary, however, to achieve the level of robustness in scientific knowledge that is required to inform protection measures of the unique Antarctic terrestrial and marine ecosystems, and their contributions to global biodiversity and ecosystem services

Untangling the influence of Antarctic and Southern Ocean life on clouds

Polar environments are among the fastest changing regions on the planet. It is a crucial time to make significant improvements in our understanding of how ocean and ice biogeochemical processes are linked with the atmosphere. This is especially true over Antarctica and the Southern Ocean where observations are severely limited and the environment is far from anthropogenic influences. In this commentary, we outline major gaps in our knowledge, emerging research priorities, and upcoming opportunities and needs. We then give an overview of the large-scale measurement campaigns planned across Antarctica and the Southern Ocean in the next 5 years that will address the key issues. Until we do this, climate models will likely continue to exhibit biases in the simulated energy balance over this delicate region. Addressing these issues will require an international and interdisciplinary approach which we hope to foster and facilitate with ongoing community activities and collaborations