Browsing by Subject "sea ice"

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  • Sandru, Andrei; Hyyti, Heikki; Visala, Arto; Kujala, Pentti (Elsevier, 2020)
    IFAC-PapersOnLine, Proceedings of the 21th IFAC World Congress, Berlin, Germany, 12-17 July 2020
    A sensor instrumentation and an automated process are proposed for sea-ice field analysis using ship mounted machine vision cameras with the help of inertial and satellite positioning sensors. The proposed process enables automated acquisition of sea-ice concentration, floes size and distribution. The process contains pre-processing steps such as sensor calibration, distortion removal, orthorectification of image data, and data extraction steps such as sea-ice floe clustering, detection, and analysis. In addition, we improve the state of the art of floe clustering and detection, by using an enhanced version of the k-means algorithm and the blue colour channel for increased contrast in ice detection. Comparing to manual visual observations, the proposed method gives significantly more detailed and frequent data about the size and distribution of individual floes. Through our initial experiments in pack ice conditions, the proposed system has proved to be able to segment most of the individual floes and estimate their size and area.
  • Vihanninjoki, Vesa (Finnish Environment Institute, 2014)
    Reports of the Finnish Environment Institute 41/2014
    Due to the Arctic climate change and the related diminishing of Arctic sea ice cover, the general conditions for Arctic shipping are changing. The retreat of Arctic sea ice opens up new routes for maritime transportation, both trans-Arctic passages and new alternatives within the Arctic region. Hence the amount of Arctic shipping is presumed to increase. Despite the observed development, the sailing conditions in the Arctic waters will remain challenging. Thus particular attention will be required also in the future with regard to crew, fleet and other infrastructural issues. In addition to other apparent challenges and risks, the increase in Arctic shipping will lead to an increased amount of emissions. The increased emissions may have considerable and unpredictable influences to the particularly sensitive Arctic environment. With regard to emission species, especially black carbon is presumed to have climatic sig-nificance within the Arctic context. Black carbon absorbs solar radiation very effectively, and when deposited to snow or sea ice cover, it may notably alter the radiative equilibrium of the Arctic region. The increased Arctic marine activities produce black carbon emissions, whose climate impacts are assessed in this report.
  • Kaikkonen, Laura; Enberg, Sara; Blomster, Jaanika; Luhtanen, Anne-Mari; Autio, Riitta; Rintala, Janne-Markus (Springer Nature, 2020)
    Polar Biology 43 9 (2020)
    Marine microbial communities undergo drastic changes during the seasonal cycle in high latitude seas. Despite the dominance of microbial biomass in the oceans, comprehensive studies on the seasonal changes of microbial plankton during the complete winter period are lacking. To study the seasonal variation in abundance of the microbial community, water samples were collected weekly in the Northern Baltic Sea from October to May. During ice cover from mid-January to April, samples from the sea ice and the underlying water were taken in addition to the water column samples. Abundances of bacteria, virus-like particles, nanoflagellates, and chlorophyll a concentrations were measured from sea ice, under-ice water, and the water column, and examined in relation to environmental conditions. All studied organisms had clear seasonal changes in abundance, and the sea-ice microbial community had an independent wintertime development compared to the water column. Bacteria were observed to have a key role in the biotic interactions in both ice and the water column, and the dormant period during the cold-water months (October–May) was limited to before ice formation. Our results provide the first insights into the temporal dynamics of bacteria and viruses during the whole cold-water season (October–May) in coastal high latitude seas, and demonstrate that changes in the environmental conditions are likely to affect bacterial dynamics and have implications on trophic interactions.
  • Eronen-Rasimus, Eeva Liisa; Kaartokallio, Hermanni; Lyra, Christina; Autio, Riitta; Kuosa, Harri; Dieckmann, Gerhard S.; Thomas, David N. (2014)
  • Tison, J. -L.; Schwegmann, S.; Dieckmann, G.; Rintala, J. -M.; Meyer, H.; Moreau, S.; Vancoppenolle, M.; Nomura, D.; Engberg, S.; Blomster, L. J.; Hendrickx, S.; Uhlig, C.; Luhtanen, A. -M.; de Jong, J.; Janssens, J.; Carnat, G.; Zhou, J.; Delille, B. (2017)
    Sea ice is a dynamic biogeochemical reactor and a double interface actively interacting with both the atmosphere and the ocean. However, proper understanding of its annual impact on exchanges, and therefore potentially on the climate, notably suffer from the paucity of autumnal and winter data sets. Here we present the results of physical and biogeochemical investigations on winter Antarctic pack ice in the Weddell Sea (R. V. Polarstern AWECS cruise, June-August 2013) which are compared with those from two similar studies conducted in the area in 1986 and 1992. The winter 2013 was characterized by a warm sea ice cover due to the combined effects of deep snow and frequent warm cyclones events penetrating southward from the open Southern Ocean. These conditions were favorable to high ice permeability and cyclic events of brine movements within the sea ice cover (brine tubes), favoring relatively high chlorophyll-a (Chl-a) concentrations. We discuss the timing of this algal activity showing that arguments can be presented in favor of continued activity during the winter due to the specific physical conditions. Large-scale sea ice model simulations also suggest a context of increasingly deep snow, warm ice, and large brine fractions across the three observational years, despite the fact that the model is forced with a snowfall climatology. This lends support to the claim that more severe Antarctic sea ice conditions, characterized by a longer ice season, thicker, and more concentrated ice are sufficient to increase the snow depth and, somehow counterintuitively, to warm the ice.
  • Qasim, Muhammad Suleman; Lampi, Mirka; Heinonen, Minna-Maria Kristiina; Garrido-Zabala, Berta; Bamford, Dennis; Käkelä, Reijo; Roine, Elina; Sarin, Peter (2021)
  • Oikkonen, Annu (Finnish Meteorological Institute, 2017)
    Finnish Meteorological Institute Contributions 138
    The state of the sea ice cover results from an interplay between thermodynamics and dynamics. Changes in the ice cover further affect the way in which the ice responds to forcing, both thermodynamic and dynamic. This thesis discusses several aspects of sea ice thermodynamics and dynamics, and their contribution to the evolution of ice pack, and particularly to changes in the Arctic sea ice cover. The main focus is on the ice dynamics in different types of ice zones and under different conditions, which also enables the examination of the impact of thermodynamic forcing on sea ice dynamics. Changes in the Arctic sea ice thickness distribution during the period 1975-2000 are studied in detail, and the contribution of thermodynamics and dynamics as driving forcing is discussed. The results show that the shape of the sea ice thickness distribution has changed: the peak of the distribution has generally narrowed and shifted towards thinner ice. A prevalent feature is the loss of thick, mostly deformed ice, which has had a significant role in the decrease in the mean and modal ice thickness. The results also show a decrease in the seasonal variability of the mean ice thickness, but with strong regional differences. Also, the regional variability of the sea ice thickness has decreased, since the thinning has been the most pronounced in regions which formerly had the thickest ice cover. The observed changes in the regional ice draft distributions cannot be explained by local warming of the atmosphere, but changes in the ice drift patterns have had an essential impact. These results emphasize the importance of the description of sea ice dynamics in the models. Sea ice dynamics, and especially deformation, strongly affect the evolution of ice volume and properties of ice cover. There has still been a need for better understanding of the highly local and intermittent deformation process, as well as its variability that rises from different types of conditions and regions. Several aspects of these questions are covered in this thesis. With coastal and ship radar images, the study of the length scale dependency of sea ice deformation rate is extended to smaller length scales (from 100 m to 10 km) and time scales (from 10 min to 24 h) than were previously possible. Sea ice deformation rate is shown to exhibit a power law with respect to both length scale and time scale at all the scales covered. Both the overall deformation rate and the length scale dependency of deformation rate are found to depend strongly on the time scale considered. Small scale deformation is studied in different type of ice regions (coastal boundary zone, compact Arctic ice pack and marginal ice zone), and under different weather conditions. One of the key findings is the connection between air temperature and deformation rate: during warm days deformation rates are generally higher than during cold days. The deformation rate is found to respond to changes in air temperature in a time scale of days, which is clearly faster than previously assumed. This response is most likely connected to the effectiveness of the healing process. However, despite of the most effective healing during the coldest winter, the previously damaged areas are found to remain the weak points in the ice cover. This confirms that the deformation history is an important factor in determining how the ice cover responds to dynamic forcing.
  • Wang, Qingkai; Li, Zhijun; Lu, Peng; Cao, Xiaowei; Leppäranta, Matti (2018)
    The kinetic coefficient of friction μk was measured for sea ice, stainless steel, and coated steel sliding on a natural sea ice cover. The effects of normal stress (3.10–8.11 kPa), ice columnar grain orientation (vertical and parallel to the sliding direction), sliding velocity (0.02–2.97 m·s–1), and contact material were investigated. Air temperature was higher than −5.0 °C for the test duration. The results showed a decline of μk with increasing normal stress with μk independent of ice grain orientation. The μk of different materials varied, partly due to distinct surface roughnesses, but all cases showed a similar increasing trend with increasing velocity because of the viscous resistance of melt-water film. The velocity dependence of μk was quantified using the rate- and state- dependent model, and μk was found to increase logarithmically with increasing velocity. In addition, μk obtained at higher air temperatures was greater than at lower temperatures. The stick-slip phenomenon was observed at a relatively high velocity compared with previous studies, which was partly due to the low-stiffness device used in the field. Based on the experimental data, the calculation of physical models can be compared.
  • van Leeuwe, Maria A.; Tedesco, Letizia; Arrigo, Kevin R.; Assmy, Philipp; Campbell, Karley; Meiners, Klaus M.; Rintala, Janne-Markus; Selz, Virginia; Thomas, David N.; Stefels, Jacqueline (2018)
    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.
  • Campbell, Karley; Matero, Ilkka; Bellas, Christopher; Turpin-Jelfs, Thomas; Anhaus, Philipp; Graeve, Martin; Fripiat, Francois; Tranter, Martyn; Landy, Jack Christopher; Sanchez-Baracaldo, Patricia; Leu, Eva; Katlein, Christian; Mundy, C. J; Rysgaard, Søren; Tedesco, Letizia; Haas, Christian; Nicolaus, Marcel (Royal Swedish Academy of Sciences, 2022)
    Sea ice continues to decline across many regions of the Arctic, with remaining ice becoming increasingly younger and more dynamic. These changes alter the habitats of microbial life that live within the sea ice, which support healthy functioning of the marine ecosystem and provision of resources for human-consumption, in addition to influencing biogeochemical cycles (e.g. air–sea CO2 exchange). With the susceptibility of sea ice ecosystems to climate change, there is a pressing need to fill knowledge gaps surrounding sea ice habitats and their microbial communities. Of fundamental importance to this goal is the development of new methodologies that permit effective study of them. Based on outcomes from the DiatomARCTIC project, this paper integrates existing knowledge with case studies to provide insight on how to best document sea ice microbial communities, which contributes to the sustainable use and protection of Arctic marine and coastal ecosystems in a time of environmental change.
  • Zu, Y.; Lu, P.; Leppäranta, Matti; Cheng, B.; Li, Z. (2021)
    The bottom topography of ridged sea ice differs greatly from that of other sea-ice types. The form drag of ridge keels has an important influence on sea-ice drift and deformation. In this study, both laboratory experiment (LabE) and fluid dynamics numerical simulation (FDS) have been carried out for a physical ridge model in a tank to better understand the quantitative characteristics of the form drag. The LabEs covered both laminar and turbulent conditions. The local form drag coefficient of a keel, C-dw, varied with the keel depth h(w) and the slope angle alpha(w) in the turbulent regime. After validated by the LabE measurements, the FDSs were employed to extend the parameterization from the finite water depth to deep water. The results gave C-dw = 0.68 center dot ln (alpha(w)/7.8 degrees), R-2 = 0.998, 10 degrees = 0.01), the variation of the local form drag coefficient and its contribution to total drag coefficient were sensitive to the keel slope angle. Assuming the log-normal distribution for this angle, the average value of the local form drag coefficient was 0.75, recommended for sea-ice dynamic models.
  • Jokinen, Pauli; Pirinen, Pentti; Kaukoranta, Juho-Pekka; Kangas, Antti; Alenius, Pekka; Eriksson, Patrick; Johansson, Milla; Wilkman, Sofia (Ilmatieteen laitos - Finnish Meteorological Institute, 2021)
    Raportteja - Rapporter - Reports 2021:8
    Tässä raportissa on ilmanpaineen, lämpötilan, suhteellisen kosteuden, sademäärän, lumensyvyyden, tuulen, auringonpaisteen ja kokonaissäteilyn ilmastotilastoja vertailukaudelta 1991–2020. Lisäksi on ensimmäistä kertaa tuotettu vertailukaudelle meritilastoja vedenkorkeudesta, veden pintalämpötilasta ja merijäästä. Havaintoasemien ja hila-aineiston perusteella on uuden 1991–2020 vertailukauden Suomen keskilämpötila noin 0,6 astetta edellistä 1981–2010 vertailukautta lämpimämpi. Verrattuna jaksoon 1961–1990 on uusi vertailukausi noin 1,3 astetta lämpimämpi. Ilmastollisia ja merellisiä tilastoja voidaan hyödyntää esimerkiksi ajankohtaisen sää- ja meriolosuhteiden laittamisessa historialliseen viitekehykseen. Lisäksi tilastoista on apua muun muassa kuukausien päähän ulottuvien sääriippuvaisten päätösten tekemisessä sekä ilmastonmuutoksen etenemisen seurannassa. Vertailukauden tilastot ovat tuotettu Maailman ilmatieteen järjestön (WMO) ohjeiden mukaisesti. Edellisten vertailukausien tapaan on esimerkiksi puuttuvien havaintojen määrässä käytetty kansallisesti tiukempia rajoja kuin WMO:n ohjeissa on kehotettu. Jakso 1991–2020 on sekä kansainvälisesti että Suomessa virallinen vertailukausi ennen kuin seuraava vertailukausi eli 2001–2030 otetaan käyttöön.