Application of Remote Sensing to the Estimation of Sea Ice Thickness Distribution

Non

Sea ice thickness estimated from passive microwave radiometers

This study presents the findings of research into the correlation between sea ice thickness and passive microwave radiation. In-situ sea ice thickness samples were obtained from video observations by the icebreaker Soya during 1996-1998 and surface feature observations in 1997 by the visible and near-infrared radiometer AVNIR mounted on the ADEOS satellite. These sea ice thickness data were binned into grid cell data of the satellite microwave radiometer SSM/I for the same location, and averaged to provide an average ice thickness for a grid cell. In order to survey the relationship between sea ice thickness and microwave radiation, two sea ice classification parameters for SSM/I were investigated as to their ability to estimate sea ice thickness. One sea ice classification parameter is the Polarization Ratio (PR), which was developed for a seasonally ice covered area and can distinguish three ice types: new ice, young ice, and first-year ice. Another parameter is the ratio between 37GHz vertical polarization and 85GHz vertical polarization (R_). It can distinguish fast ice in addition to the three ice types that can be distinguished by the PR. These parameters showed correlation coefficients with in-situ sea ice thickness, -0.77 and 0.67, respectively, in this study. Estimated sea ice thickness derived from multiple regression analysis using PR and R_ showed good correlation (R=0.81) with in-situ sea ice thickness

In-situ ice and meteorological observations in the southern Sea of Okhotsk in 2001 winter: ice structure, snow on ice, surface temperature, and optical environments

The 2001-ice season in the Sea of Okhotsk was characterized by extraordinarily developed ice extent. During the period February 17 to 21, we conducted in-situ observations in the southern ice area with the icebreaker \u27Soya\u27. In this paper, we show the observational results, concerning the core sampling of about 1.3 m-thick ice, snow sampling, surface temperature, and solar radiation under clear sky conditions. It is shown that (1) the sampled ice core is composed entirely of granular ice, (2) the 30 cm-thick snow pack overlying sea ice is composed mainly of depth hoar and significant vertical gradients of δ^O and temperature are found within the snow, probably associated with the depth hoar formation, (3) surface temperatures as low as about -30°C are detected on snow-covered sea ice floes at nighttime under almost clear and light breeze conditions, (4) from the estimation of the turbidity coefficient, the atmosphere over the ice-covered area is considered to be significantly clean. Furthermore, the NOAA/AVHRR satellite data are used to estimate the surface temperature distribution in the southern Sea of Okhotsk. It is shown that these data are useful for discriminating thick ice floes

Sea ice melt affects algal photosynthesis and growth: A laboratory study on an ice algal community from the Sea of Okhotsk

The Tenth Symposium on Polar Science/Ordinary sessions: [OB] Polar Biology, Wed. 4 Dec. / 3F Multipurpose conference room, National Institute of Polar Researc

Analysis on the crystals of sea ice cores derived from Weddell Sea, Antarctica

In order to understand the sea ice types and its region of origin frozen in Weddell Sea, 27 ice cores were taken from Weddell Sea, Antarctica during September and October, 2006. Their crystals were analyzed, and their ice forming processes were evaluated based on the crystals. Photos of the thin sections from two whole ice cores, and from polygonal granular superimposed ice were taken as well as corresponding stratigraphy descriptions. Vertical profiles of salinity, density and grain size were also obtained. Based on ice core structural texture, the findings include that: 1) although large and smooth ice floes were selected as the investigation sites, the ice sheet at the sampling position may be formed by rafted ice, consolidated ice ridges and second-year ice which were affected by dynamic and thermodynamic processes together subsequently. Ice formed in pure thermal growth comprises minority. The polygonal granular superimposed ice from refrozen wetted dense snow is one type of the ice in Antarctica. 2) Of the all 27 ice cores, the granular, mixed granular-columnar and columnar crystals in sea ice occupy 28.7%, 14.4% and 55.2%, respectively. 3) The pure thermal growth ice is predominant in marginal sea ice zone; the rafted ice and consolidated ice ridges, even second-year ice and polygonal granular superimposed ice from dynamic and thermal effects were found in front of Larsen A Ice Shelf; the thermal growth ice froze in the polynyas of Larsen A, and was transferred outwards

Lake ice formation processes and thickness evolution at Lake Abashiri, Hokkaido, Japan

第6回極域科学シンポジウム[OM] 極域気水圏11月16日（月）　国立極地研究所１階交流アトリウ

Observation of anomalous spectral downshifting of waves in the Okhotsk Sea Marginal Ice Zone

Waves in the Marginal Ice Zone in the Okhotsk Sea are less studied compared to the Antarctic and Arctic. In February 2020, wave observations were conducted for the first time in the Okhotsk Sea, during the observational program by Patrol Vessel Soya. A wave buoy was deployed on the ice, and in situ wave observations were made by a ship-borne stereo imaging system and Inertial Measurement Unit. Sea ice was observed visually and by aerial photographs by drone, while satellite synthetic aperture radar provided basin-wide spatial distribution. On 12 February, a swell system propagating from east northeast was detected by both the stereo imaging system and the buoy-on-ice. The wave system attenuated from 0.34 m significant wave height to 0.25 m in about 90 km, while the wave period increased from 10 s to 15–17 s. This anomalous spectral downshifting was not reproduced by numerical hindcast and by applying conventional frequency-dependent exponential attenuation to the incoming frequency spectrum. The estimated rate of spectral downshifting, defined as a ratio of momentum and energy losses, was close to that of uni-directional wave evolution accompanied by breaking dissipation: this indicates that dissipation-driven nonlinear downshifting may be at work for waves propagating in ice

ナンタイヨウ ニ オケル コウセツ ノ サンソ アンテイ ドウイタイヒ ノ ケイド ブンプ ト キセツ ヘンカ

降雪の酸素安定同位体比(δ^O)の緯度分布と季節変化の存在はよく知られているが,極域海洋上での降雪のδ^O の報告はほとんどない.本研究では,南大洋高緯度域において,夏季と冬季の4つの現場海洋観測の機会を利用し,船上に降った雪を採取し分析した.また,通年のデータとして,2008年における昭和基地での降雪のサンプルを分析した.これらに基づいて,南大洋上の降雪のδ^O の緯度分布と季節変化について考察する.全般に高緯度ほど低く,また夏季より冬季の方が低いδ^O の分布が得られた.また,緯度変化の傾きは冬季の方が強い.夏季および冬季のδ^O は,60°Sにおいて-5.4‰と-11.3‰であるのに対し,66°Sにおいて-10.5‰と-20.8‰であった.これらの結果は,南極海での塩分分布やその変化のメカニズムを解明する上での手助けになると考えられる.The stable oxygen isotope ratio(δ^O) in precipitation is known to have important meridional and seasonal variations, but there are almost no measurements of δ^O in precipitation over polar oceans. The present research took advantage of 4 opportunities for in situ observations in summer and winter at high latitudes in the Southern Ocean. In addition, we analyzed samples of precipitation at Syowa Station in 2008 to obtain year-round data. Based on these data, we consider the meridional and seasonal variations of δ^O in precipitation over the Southern Ocean. In general, δ^O decreases with increasing latitude, and is lower in winter than in summer. The latitude gradient is stronger in winter. At 60°S, δ^O is -5.4‰ and -11.3‰ in summer and winter, respectively, while the corresponding figures at 66°S are -10.5‰ and -20.8‰. These results will help us understand the mechanisms of the salinity distribution and its variation in the Antarctic Ocean