Improved Chlorophyll-a Algorithm for the Satellite Ocean Color Data in the Northern Bering Sea and Southern Chukchi Sea

이상헌,류종성,박정우,권재일,Jingping Zhao,손승현 한국해양과학기술원 2018 Ocean science journal Vol.53 No.3

The Bering and Chukchi seas are an important conduit to the Arctic Ocean and are reported to be one of the most productive regions in the world’s oceans in terms of high primary productivity that sustains large numbers of fishes, marine mammals, and sea birds as well as benthic animals. Climate-induced changes in primary production and production at higher trophic levels also have been observed in the northern Bering and Chukchi seas. Satellite ocean color observations could enable the monitoring of relatively long term patterns in chlorophyll-a (Chl-a) concentrations that would serve as an indicator of phytoplankton biomass. The performance of existing global and regional Chl-a algorithms for satellite ocean color data was investigated in the northeastern Bering Sea and southern Chukchi Sea using in situ optical measurements from the Healy 2007 cruise. The model-derived Chl-a data using the previous Chl-a algorithms present striking uncertainties regarding Chl-a concentrations – for example, overestimation in lower Chl-a concentrations or systematic overestimation in the northeastern Bering Sea and southern Chukchi Sea. Accordingly, a simple two band ratio (Rrs(443)/Rrs(555)) algorithm of Chl-a for the satellite ocean color data was devised for the northeastern Bering Sea and southern Chukchi Sea. The MODIS-derived Chl-a data from July 2002 to December 2014 were produced using the new Chl-a algorithm to investigate the seasonal and interannual variations of Chl-a in the northern Bering Sea and the southern Chukchi Sea. The seasonal distribution of Chl-a shows that the highest (spring bloom) Chl-a concentrations are in May and the lowest are in July in the overall area. Chl-a concentrations relatively decreased in June, particularly in the open ocean waters of the Bering Sea. The Chl-a concentrations start to increase again in August and become quite high in September. In October, Chl-a concentrations decreased in the western area of the Study area and the Alaskan coastal waters. Strong interannual variations are shown in Chl-a concentrations in all areas. There is a slightly increasing trend in Chl-a concentrations in the northern Bering Strait (SECS). This increasing trend may be related to recent increases in the extent and duration of open waters due to the early break up of sea ice and the late formation of sea ice in the Chukchi Sea.

베링해 해빙 상태와 척치해 해빙 변화 간의 연관성 분석: 정보 엔트로피 접근

오민기,김현철 대한원격탐사학회 2018 大韓遠隔探査學會誌 Vol.34 No.6

본 연구에서는 위성영상 기반의 북극의 해빙 농도 시계열 데이터를 이용하여 베링해의 해빙 상태가 척치해 해빙 농도 변화의 전조로서 작용할 수 있는지를 실험하였다. 해빙 농도 자료는 1982년부터 2017년의 36년간의 월평균 시계열 데이터로 이뤄져 있으며, 베링해의 해빙 농도와 척치해 해빙 농도 사이의 관계성을 전송 엔트로피 측정을 통해 분석하였다. 전송 엔트로피는 두 개의 확률변수 또는 신호 간의 비선형적 연관성을 파악하게 해주는 동시에 변수 사이의 시간 간격 조절을 통해 인과관계를 추정할 수 있는 측정이다. 해빙 농도를 대상으로 한 측정 결과, 베링해의 과거 3, 5, 6개월 전의 해빙 농도값이 척치해 해빙의 변화에 관련되어 있음을 알수 있었다. 특히, 베링해의 해빙 농도값이 극소를 나타냈을 때, 5개월 후의 척치해의 해빙 농도는 감소될 확률이 약 70%로 나타났다. 이는 태평양에서 베링해협을 통해 북극해로 유입되는 해류가 베링해의 해빙 농도를 감소시킨 후 해협을 통해 척치해로 이동하여 해빙을 녹이는 과정에 비롯한 것으로 사료된다. 향후 위성데이터에 정보 이론으로 접근하는 이 연구를 더 발전시켜 어떤 시점과 시간적 스케일로 특이 패턴이 발생하는지 조사하고 그 기간에 관련된 해양-대기의 패턴 또는 사건들을 분석하여, 떨어진 두 지역의 해빙 농도 상태에 내재된 연관성에 대한 심층적 이해가 가능할 것이다. We examined if a state of sea-ice in Bering Sea acts as a prelude of variation in that of Chukchi Sea by using satellites-based Arctic sea-ice concentration time series. Datasets consist of monthly values of sea-ice concentration during 36 years (1982-2017). Time series analysis armed with Transfer entropy is performed to describe how sea-ice data in Chukchi Sea is affected by that in Bering Sea, and to explain the relationship. The transfer entropy is a measure which identifies a nonlinear coupling between two random variables or signals and estimates causality using modification of time delay. We verified this measure checked a nonlinear coupling for simulated signals. With sea-ice concentration datasets, we found that sea-ice in Bering Sea is influenced by that in Chukchi Sea 3, 5, 6 months ago through the transfer entropy measure suitable for nonlinear system. Particularly, when a seaice concentration of Bering Sea has a local minimum, sea ice concentration around Chukchi Sea tends to decline 5 months later with about 70% chance. This finding is considered to be a process that inflow of Pacific water through Bering strait reduces sea-ice in Chukchi Sea after lowering the concentration of sea-ice in Bering Sea. This approach based on information theory will continue to investigate a timing and time scale of interesting patterns, and thus, a coupling inherent in sea-ice concentration of two remote areas will be verified by studying ocean-atmosphere patterns or events in the period.

북극권의 진출로 오호츠크 해와 베링 해 지역연구: 선적활동과 장애요인

한종만 배재대학교 한국-시베리아센터 2018 한국시베리아연구 Vol.22 No.1

Global warming in the Arctic region is twice as fast as that in other regions. Arctic sea ice in summer keeps renewing its lowest extent every year since 2010, which has been monitored by satellite observations since 1970s. This decrease of Arctic sea ice is expected to benefit the usage of the Arctic route, and developments and utilizations of energy, fishery, and ecotourism resources in the Arctic Circle. The vessels in the Russian Far East and the vessels of Korea, China, and Japan using Arctic shipping route, which includes the Northeast Passage, the Northwest Passage, and the Transpolar Sea Route, trail the Bering Strait, through the East Sea, the Sea of Okhotsk, and the Bering Sea. Therefore, developments in the Arctic region and shipping activities across the Bering Strait are expected to increase steadily. Although the developments and increased shipping activities can raise risks of accidents and harm the ecosystem, not only infrastructure for prevention and post-management of accidents is lacking, but also national, bilateral, and multilateral governance system for environmental protection has not been settled. Sustainable ecosystems should be taken into account in the developments, uses of the Arctic route, and the governance. In this article, Chapter 2 outlines the physical and human geographical characteristics of the Sea of Okhotsk and the Bering Sea. Chapter 3, the current status and analysis of marine activity in the study area, contemplates the trade structure and current status of importation and exportation, ports, and shipment through the Aleutian Islands and the Bering Strait. Chapter 4 explores the obstacles to the Arctic route and activation strategies for the route. 북극 지역의 온난화는 기타 지역보다 2배나 빠르게 상승하고 있으며, 1970년대 인공위성 관측을 시작한 이래 2010년부터 여름철 북극해 얼음 규모는 매번 최소치를 갱신하고 있다. 북극해의 해빙으로 북극항로의 이용과 북극권의 자원/에너지 개발, 수산자원의 활동, 생태관광자원의 이용가능성을 높여주고 있다. 러시아 극동지역과 한중일의 선박은 동해 , 오호츠크 해, 베링 해를 거쳐 베링해협을 통과해야만 가능한 북극항로는 북동항로, 북서항로, 북 극점 경유 항로로 구분된다. 북극개발과 베링해협 통과 선적활동은 꾸 준히 증가할 것으로 예상된다. 북극권 개발과 선적활동과 증가로 야기되는 여러 형태의 사고 위험 성과 부정적 생태계의 변화 가능성도 병행되고 있으며, 사전 및 사후 사고 예방을 위한 인프라 시설의 부족과 부재뿐만 아니라 환경보호를 위한 국가별, 쌍무간, 다자간 거버넌스 시스템도 정착되지 않은 상황이 다. 개발과 항로 이용과 거버넌스는 지속가능한 생태계에 기반을 둔 차 원에서 이루어져야만 한다. 이러한 맥락에서 본 논문 제2장은 오호츠크 해, 베링해협과 베링 해 남부와 북부 지역의 자연 및 인문 지리적 특성을 개관한 후 제3장 연 구공간 해양활동의 현황과 분석에서는 수출입 현황과 구조, 항구 현황, 알류샨열도와 베링해협 통과 선적 현황을 고찰한다. 제4장에서는 북극 항로의 장애요인과 활성화 방안을 모색한다.

Latitudinal variation of phytoplankton communities in the western Arctic Ocean

Min Joo, H.,Lee, S.H.,Won Jung, S.,Dahms, H.U.,Hwan Lee, J. Pergamon Press 2012 Deep-sea research. Part II, Topical studies in oce Vol.81 No.-

Recent studies have shown that photosynthetic eukaryotes are an active and often dominant component of Arctic phytoplankton assemblages. In order to explore this notion at a large scale, samples were collected to investigate the community structure and biovolume of phytoplankton along a transect in the western Arctic Ocean. The transect included 37 stations at the surface and subsurface chlorophyll a maximum (SCM) depths in the Bering Sea, Chukchi Sea, and Canadian Basin from July 19 to September 5, 2008. Phytoplankton (>2μm) were identified and counted. A cluster analysis of abundance and biovolume data revealed different assemblages over the shelf, slope, and basin regions. Phytoplankton communities were composed of 71 taxa representing Dinophyceae, Cryptophyceae, Bacillariophyceae, Chrysophyceae, Dictyochophyceae, Prasinophyceae, and Prymnesiophyceae. The most abundant species were of pico- to nano-size at the surface and SCM depths at most stations. Nano- and pico-sized phytoplankton appeared to be dominant in the Bering Sea, whereas diatoms and nano-sized plankton provided the majority of taxon diversity in the Bering Strait and in the Chukchi Sea. From the western Bering Sea to the Bering Strait, the abundance, biovolume, and species diversity of phytoplankton provided a marked latitudinal gradient towards the central Arctic. Although pico- and nano-sized phytoplankton contributed most to cell abundance, their chlorophyll a contents and biovolumes were less than those of the larger micro-sized taxa. Micro-sized phytoplankton contributed most to the biovolume in the largely ice-free waters of the western Arctic Ocean during summer 2008.

Late Pliocene to early Pleistocene (2.4-1.25Ma) paleoproductivity changes in the Bering Sea: IODP expedition 323 Hole U1343E

Kim, S.,Khim, B.K.,Takahashi, K. Pergamon Press 2016 Deep-sea research. Part II, Topical studies in oce Vol.125 No.-

Late Pliocene to early Pleistocene paleoproductivity changes in the Bering Sea were reconstructed using geochemical concentrations and mass accumulation rates (MARs) of CaCO<SUB>3</SUB>, biogenic opal, and total organic carbon (TOC), and sedimentary nitrogen isotope ratios (δ<SUP>15</SUP>N) at IODP Expedition 323 Hole U1343E, drilled in the northern slope area (1956m deep) of the Bering Sea. CaCO<SUB>3</SUB> concentration is generally low, but prominent CaCO<SUB>3</SUB> peaks occur intermittently due to subseafloor authigenic carbonate formation rather than biogenic accumulation, regardless of glacial-interglacial variations. Biogenic opal concentrations reflect orbital-scale glacial-interglacial variations. However, TOC concentration did not show clear glacial-interglacial variation, probably due to poor preservation. The sedimentary δ<SUP>15</SUP>N values vary synchronously with biogenic opal concentration on orbital timescales. The co-varying pattern of opal productivity and δ<SUP>15</SUP>N values at Hole U1343E is a result of nutrient utilization controlled by diatom productivity in the Bering slope area where Fe is not a limiting factor. Biogenic opal and TOC MARs showed a temporal shift at around 1.9Ma from a high productivity period under nutrient-enriched conditions to a low productivity period under relatively nutrient-depleted conditions. High diatom productivity with low δ<SUP>15</SUP>N values before 1.9Ma is associated with abundant nutrient supply by upwelling in relation to strong surface current system. This productivity decrease at about 1.9Ma was also found in the southern Bering Sea (Site U1341) and may be related to global opal reorganization.

Orbital-scale benthic foraminiferal oxygen isotope stratigraphy at the northern Bering Sea Slope Site U1343 (IODP Expedition 323) and its Pleistocene paleoceanographic significance

Asahi, H.,Kender, S.,Ikehara, M.,Sakamoto, T.,Takahashi, K.,Ravelo, A.C.,Alvarez Zarikian, C.A.,Khim, B.K.,Leng, M.J. Pergamon Press 2016 Deep-sea research. Part II, Topical studies in oce Vol.125 No.-

A continuous composite oxygen isotope (δ<SUP>18</SUP>O) stratigraphy from benthic foraminifera in the Bering Sea was reconstructed in order to provide insight into understanding sea-ice evolution in response to Northern Hemisphere Glaciation. Oxygen isotope records from multiple species of benthic foraminifera at Integrated Ocean Drilling Program (IODP) Expedition 323 Site U1343 (54<SUP>o</SUP>33.4'N, 176<SUP>o</SUP>49.0'E, water depth 1950m) yield a highly refined orbital-scale age model spanning the last 1.2Ma, and a refined age model between 1.2 and 2.4Ma. An inter-species calibration was used to define species offsets and to successfully obtain a continuous composite benthic δ<SUP>18</SUP>O record, correlated with the global composite benthic δ<SUP>18</SUP>O stack curve LR04 to construct an orbital-scale age model. The consistency of the benthic δ<SUP>18</SUP>O stratigraphy with biostratigraphy and magnetostratigraphy confirms the reliability of both methods for constraining age. The time difference between cyclic changes in sedimentary physical properties and glacial-interglacial cycles since 0.8Ma is notable, and suggests that physical properties alone cannot be used to construct an orbital-scale age model. Amplitude changes in physical properties and a significant drop in the linear sedimentation rate during glacials after 0.9Ma indicate that the glacial sea-ice edge extended beyond the Bering Sea Slope (Site U1343) at this time.

Biomass of Bacterioplankton and Protists and Their Ecological Importance in the Bering Sea

He, Jianfeng,Chen, Bo,Kang, Sung-Ho,Zeng, Yinxin,Cai, Minghong Korea Institute of Ocean ScienceTechnology 2004 Ocean and Polar Research Vol.26 No.2

The abundance, biomass and distribution of phytoplankton, bacterioplankton and heterotrophic protists in the Bering Sea were investigated from July to August 1999. Chlorophyll a concentrations in the surface waters ranged from 0.16 to $3.79{\mu}g\;l^{-1}$ Nano-phytoplankton were found to constitute from 63 to 98% of the total phytoplankton biomass, and were clearly the dominant primary producers. The biomass of bacterioplankton in the surface layers varied from 1.46 to $20.2{\mu}g\;C\;l^{-1}$ and accounted for 30% of the total phytoplankton biomass. The biomass of bacterioplankton integrated over a depth of 0 to 100m averaged 65.4% of the total phytoplankton biomass. The surface biomass of heterotrophic protists ranged from 1.2 to $27.4{\mu}g\;C\;l^{-1}$, and was within the same order of magnitude as that of bacterioplankton. Of the total biomass of heterotrophic protists in the upper 100m of the water column, 65% was attributed to protists in the nano-size class. The results of this study suggest that bacteria and nano-protists are important components of the planktonic community in the Bering Sea during the summer season. The abundance of bacterioplankton and planktonic protists decreased from the western to northeastern and eastern regions of the Bering Sea. The abundance of these organisms also decreased with depth. The available evidence suggests that variation in the abundance and distribution of these organisms may be affected by water currents and vertical temperature variation in the Bering Sea.

High Organic Carbon Deposition in the Northern Margin of the Aleutian Basin (Bering Sea) before the Last Deglaciation

김부근,김성한,Masao Uchida,Takuya Itaki 한국해양과학기술원 2010 Ocean science journal Vol.45 No.4

High-resolution geochemical, isotope and elemental data from core PC23A in the northern margin of the Aleutian Basin (Bering Sea) were used to reconstruct distinct paleoceanographic features of the last deglaciation (pre-Boreal[PB], Bølling-Allerød[BA], Younger Dryas[YD]). The PB and BA intervals are characterized by increased siliceous (diatom) and calcareous (coccolithophores and foraminifers) productivity represented by high biogenic opal and CaCO3 contents, respectively. The enhanced productivity can plausibly be attributed to an elevated sea-surface nutrient supply from increased melt-water input and enhanced Alaskan Stream injection under warm, restricted sea-ice conditions. High Corg/N ratios and low δ13C values of sediment organic matter during the PB and BA intervals reflect the contribution of terrestrial organic matters. The PB and BA intervals were also identified by laminated sediment layers of core PC23A, characterized by high Mo/Al and Cd/Al ratios, indicating that the bottom water condition remained anoxic. High δ15N values during the same period were attributed mainly to the increased nutrient utilization and subsequent denitrification of seawater nitrate. Part of high δ15N values may also be due to incorporation of inorganic nitrogen in the clay minerals. It is worthy of note that high total organic carbon (TOC) deposition occurred approximately 3,000 years before onset of the last deglaciation. Simultaneous high Corg/N ratios and low δ13C values clearly suggest that the high TOC content should be related to terrestrial organic carbon input. Low δ15N values during the high TOC interval also confirm the contribution of terrigenous organic matter. Although abundant calcareous phytoplankton production under cold, nutrient-poor conditions represented by Baex data was reported for high TOC deposition preceding the last deglaciation in an earlier study of the Okhotsk Sea, the main reason for the enhanced TOC deposition in the Bering Sea is an increased terrigenous input from the submerged continental shelves (Beringia) with a sea-level rise; this is further supported by Al enrichment of bulk sediments during the high TOC deposition.

반구대 암각화의 작살잡이와 우미악(Umiak)

송화섭(Song, Hwa-Seob) 비교민속학회 2012 비교민속학 Vol.0 No.49

울산 반구대 암각화에는 고래 문양이 매우 사실적으로 묘사되었다. 반구대의 고래암각화는 고래에 대한 생태 지식과 관찰력이 매우 뛰어난 집단의 작품임을 쉽게 판명할 수 있다. 고래 문양의 조각 기법과 표현 양식이 매우 정교하고 회화성(繪?性)이 매우 우수하기 때문이다. 이와 같은 그림은 고래잡이 전문집단의 작품으로 추정한다. 고래잡이 전문 사냥꾼들은 바다에서 고래잡이를 생업으로 하는 해양수렵 집단이라 할 수 있다. 해양수렵은 바다동물을 전문적으로 사냥하는 집단의 생활방식을 말한다. 북아시아 내륙에서는 유목과 사냥을 하는 유목수렵민들이 있듯이, 북아시아 해안, 바다에도 바다동물을 사냥하는 해양수렵민들이 있다. 해양수렵민들은 1년 내내 바다에서 이동생활을 하면서 고래, 바다표범, 바다코끼리 등 포유류의 바다동물을 사냥하는 관습을 갖고 있다. 상시적으로 바다에서 포유류를 사냥할 수 있는 곳은 북극해(北極海)이다. 북극해는 자연 환경과 기후 여건상 雪原과 얼음지대로 덮혀있는 툰드라(tundra) 지대이기에 바다동물을 사냥하는 방법 외에 달리 생업 조건이 형성되지 않는다. 이러한 기후환경의 바다에서 포유류를 사냥하는데 고안된 배가 우미악(umiak)이다. 우미악은 바다표범의 가죽으로 만든 가죽배이다. 우미악은 바다에서 고래잡이하는데 매우 용이하게 만들어졌다. 신석기시대에 북극해에서 우미악으로 고래잡이하는 작살잡이 암각화가 백해(white sea)에서 발견되었다. 반구대 암각화는 북태평양의 고래생업지대에 속한다. 북태평양의 고래생업지대는 알래스카와 베링해협인데, 이 해역의 고래들이 가을에 새끼를 번식하고 양육하기 위하여 溫帶 바다로 이동해와 겨울을 지낸다. 북태평양 아시아권에서는 베링해와 오호츠크해에서 서식하는 고래가 한반도 울산만으로 이동해와 겨울을 지내고서 다시 회유하는 고래 생태 현상을 발견할 수 있다. 고래 이동에 따라 북아시아 고래사냥꾼들이 울산만으로 내려와 고래잡이를 하였다는 기록이 반구대 암각화에 나타난다. 반구대 암각화의 배 그림은 우미악을 표현한 것이며, 우미악을 이용하여 작살잡이하는 그림은 북아 시아 고래잡이 암각화와 같은 계통이다. 따라서 반구대 암각화는 베링해협에서 고래잡이 전문집단이 도래하여 제작한 것으로 보인다. A whale is sculpted in detail in the petroglyph in Bangudae, Ulsan. The petroglyph shows that it is a work of people who had a knowledge on whales and observed them keenly. Collectively, it is considered to be a work of a group of professional whale hunters since the sculpturing techniques and expressions used in the petroglyph were very delicate and excellent. For the people hunting whales was their profession. In the inland of North Asia, there were nomadic people who lived by hunting land animals while there were people who hunted sea animals in the coast area of North Asia. People who hunted sea animals moved and caught whales, seals, walrus in the Artic Ocea around the year. There is tundra in the Artic regions which has no trees but snow and ice so the residents had to hunt sea animals. This environment made them develop Umiak, a special ship to hunt sea animals. Umiak is made of harbour seal skin and it was convenient to catch whales. There is a petroglyph on people who hunted a whale using Umiak in the Artic Ocean in the Stone Age. The Bangudae petroglyph is included into the art in whale hunting areas of the Artic Ocean which are Alaska and the straits of Bering. The whales live there give birth in the fall and move to the warm latitude in the winter to raise their babies. There are whales who come to Ulsan gulf for winter from the Bering Sea and Sea of Okhotsk and go back there after the winter in the Pacific Ocean near Asia. The Bangudae petroglyph also shows that whale hunters from North Asia came to the Ulsan gulf to catch whales. The ship in the Bangudae petroglyph is Umiak and it suggests that the petroglyph is classified as the same one found in the North Asia. Consequently, the Bangudae petroglyph is assumed to be sculpted by a group of professional whale hunters who were from the straits of the Bering.

Genetic Stock Identification of Immature Chum Salmon (Oncorhynchus keta) in the Western Bering Sea, 2004

강민호,김수암,Loh-Lee Low 한국해양과학기술원 2016 Ocean science journal Vol.51 No.2

Genetic stock identification studies have been widely applied to Pacific salmon species to estimate stock composition of complex mixed-stock fisheries. In a September−October 2004 survey, 739 chum salmon (Oncorhynchus keta) specimens were collected from 23 stations in the western Bering Sea. We determined the genetic stock composition of immature chum salmon based on the previous mitochondria DNA baseline. Each regional estimate was computed based on the conditional maximum likelihood method using 1,000 bootstrap resampling and then pooled to the major regional groups: Korea - Japan - Primorie (KJP) / Russia (RU) / Northwest Alaska (NWA) / Alaska Peninsula - Southcentral Alaska - Southeast Alaska - British Columbia - Washington (ONA). The stock composition of immature chum salmon in the western Bering Sea was a mix of 0.424 KJP, 0.421 RU, 0.116 NWA, and 0.039 ONA stocks. During the study period, the contribution of Asian chum salmon stocks gradually changed from RU to KJP stock. In addition, North American populations from NWA and ONA were small but present near the vicinity of the Russian coast and the Commander Islands, suggesting that the study areas in the western Bering Sea were an important migration route for Pacific chum salmon originating both from Asia and North America during the months of September and October. These results make it possible to better understand the chum salmon stock composition of the mixed-stock fisheries in the western Bering Sea and the stock-specific distribution pattern of chum salmon on the high-seas.