Исследование ледовой обстановки Обской губы по современным спутниковым данным в 2007–2017 гг.

The Obskay guba Bay is a region of rapidly developing oil and gas exploration. Knowing the current sea ice conditions including dangerous phenomena e. g. ridges and stamukhas is important for the safety of coastal and underwater construction as well as for ecological risk assessment. With this study, we aim to obtain new data on sea ice seasonal cycle in the southern and central part of the Obskay guba Bay for 10 years (from 2007 to 2017) and to demonstrate the capacity of satellite data in obtaining varying sea ice characteristics in the region. Analyzing daily visual MODIS and available Sentinel-1 SAR imagery, we derived dates of sea ice and fast ice formation, fast ice breakup and melt onset and the onset of ice-free period. For this purpose the satellite data were analyzed manually by sea ice expert. In addition, of sea ice ridges were derived and the sea ice drift data wea automatically processed in order to locate motionless sea ice features — stamukhas. The distribution of sea ice floes and field size in the region was derived from MODIS data. The analysis showed that there is a tendency towards a shorter ice covered period based on the data from 2007 to 2017. Overall, the formation of sea ice starts 9 days later and fast ice breakup occurs 16 days earlier compared to the long-term mean (1947–2010). The majority of ridges were located in the central part of the region and directed along the coast. The analysis confirmed absence of large stamuhas visible to be applied method (with a horizontal size of 100 m). The predominant sea ice field size range lies 500–1500 m. The study shows that a combination of images obtained in the optical range of the survey with radar data makes it possible to supplement the classical visual assessments with the results of automatic methods for detecting fast ice, detecting stamukha, as well as ice drift and deformation.Обская губа — район бурно развивающейся добычи нефти и газа. Знание текущих ледовых условий необходимо для безопасности береговой и подводной инфраструктуры. Целью данного исследования является оценка сроков ледовых явлений и отдельных характеристик (скорость дрейфа, локализация стамух и торосов) в южной и центральной части Обской губы с 2007 по 2017 г. Анализируя ежедневные визуальные данные MODIS и имеющиеся снимки Sentinel-1 SAR, мы определили даты начала устойчивого ледообразования, начало формирования и взлома припая, наступление безледного периода. В целом по данным с 2007 по 2017 г. наблюдается тенденция уменьшения существования ледяного покрова. Образование морского льда начинается позже, а взлом припая — раньше по сравнению со средними многолетними наблюдениями (1947–2010 гг.). Также были определены скорость дрейфа морского льда и распространение торосов. Отсутствие в районе крупных стамух было подтверждено результатами алгоритма автоматической обработки РСА-изображений

Sediment entrainment into sea ice and transport in the Transpolar Drift: a case study from the Laptev Sea (Winter 2011/12)

Highlights • Observations show that formation of sediment-laden sea ice occurs in coastal polynyas in winter. • Sea ice rafted sediments are a significant component of the Laptev Sea’s sediment budget. • No observational evidence for sediment entrainment into sea ice in mid-shelf polynyas at water depth greater than 20 m. Abstract Sea ice is an important vehicle for sediment transport in the Arctic Ocean. On the Laptev Sea shelf (Siberian Arctic) large volumes of sediment-laden sea ice are formed during freeze-up in autumn, then exported and transported across the Arctic Ocean into Fram Strait where it partly melts. The incorporated sediments are released, settle on the sea floor, and serve as a proxy for ice-transport in the Arctic Ocean on geological time scales. However, the formation process of sediment-laden ice in the source area has been scarcely observed. Sediment-laden ice was sampled during a helicopter-based expedition to the Laptev Sea in March/April 2012. Sedimentological, biogeochemical and biological studies on the ice core as well as in the water column give insights into the formation process and, in combination with oceanographic process studies, on matter fluxes beneath the sea ice. Based on satellite images and ice drift back-trajectories the sediments were likely incorporated into the sea ice during a mid-winter coastal polynya near one of the main outlets of the Lena River, which is supported by the presence of abundant freshwater diatoms typical for the Lena River phytoplankton, and subsequently transported about 80 km northwards onto the shelf. Assuming ice growth of 12 to 19 cm during this period and mean suspended matter content in the newly formed ice of 91.9 mg l-1 suggests that a minimum sediment load of 8.4x104 t might have been incorporated into sea ice. Extrapolating these sediment loads for the entire Lena Delta region suggests that at least 65% of the estimated sediment loads which are incorporated during freeze-up, and up to 10% of the annually exported sediment load may be incorporated during an event such as described in this paper