• Ocean and Polar Research
• /
• 제23권4호
• /
• pp.433-440
• /
• 2001

Marine organisms in Antarctica live in an environment which exhibits variability in physical processes over a wide range of temporal scales, from seconds to millennia. This time scale tends to be correlated with the spatial scale over which a given process operates, though this relationship is influenced by biology. The way organisms respond to variability in the physical environment depends on the time-scale of that variability in relation to life-span. Short-term variations are perceived largely as noise and probably have little direct impact on ecology. Of much greater importance to organisms in Antarctica are seasonal and decadal variations. Although seasonality has long been recognised as a key feature of polar environments, the realization that decadal scale variability is important is relatively recent. Long-term change has always been a feature of polar environments and may be a key factor in the evolution of the communities we see today.

• 한국제4기학회:학술대회논문집
• /
• 한국제4기학회 2006년도 춘계학술대회
• /
• pp.53-56
• /
• 2006

• Ocean and Polar Research
• /
• 제40권1호
• /
• pp.1-13
• /
• 2018

Previous studies have indicated a great regional difference in Sea Level Rise (SLR) in the Pacific and it has been suggested that this is linked to climate variability over the past two decades. In this study, we seek to identify the possible linkage between regional sea level and Pacific climate variability from altimetry-based sea level data (1993-2012) and further investigate how the Pacific sea level has changed spatially and temporally over the past 60 years from long-term sea level reconstruction data (1953-2008). Based on the same method as Zhang and Church (2012), the Inter-annual Climate Index (ICI) associated with the El $Ni{\tilde{n}}o-Southern$ Oscillation (ENSO) and the Decadal Climate Index (DCI) associated with Pacific Decadal Oscillation (PDO) are defined and then the multiple variable linear regression is used to analyze quantitatively the impact of inter-annual and decadal climate variability on the regional sea levels in the Pacific. During the altimeter period, the ICI that represents ENSO influence on inter-annual time scales strongly impacts in a striking east-west "see-saw mode" on sea levels across the tropical Pacific. On the other hand, the decadal sea level pattern that is linked to the DCI has a broad meridional structure that is roughly symmetric in the equator with its North Pacific expression being similar to the PDO, which largely contributes to a positive SLR trend in the western Pacific and a negative trend in the eastern Pacific over the two most recent decades. Using long-term sea level reconstruction data, we found that the Pacific sea levels have fluctuated in the past over inter-annual and decadal time scales and that strong regional differences are presented. Of particular interest is that the SLR reveals a decadal shift and presents an opposite trend before and after the mid-1980s; i.e., a declining (rising) trend in the western (eastern) Pacific before the mid-1980s, followed by a rising (declining) trend from the mid-1980s onward in the western (eastern) Pacific. This result indicates that the recent SLR patterns revealed from the altimeters have been persistent at least since the mid-1980s.

• 대기
• /
• 제18권4호
• /
• pp.485-492
• /
• 2008

This study confirms that a decadal variation of the SST (Sea Surface Temperature) in the WNP (Western North Pacific) has an influence on the genesis and passage ofa Tropical Cyclone. The decadal mode was obtained by calculating the SST anomaly on the domain $150^{\circ}E-190^{\circ}E$, and $5^{\circ}S-5^{\circ}N$. Such decadal variation was subsequently analyzed to confirm that it is a dominant mode in central Pacific region. Next, after classifying the years into relatively positive years and relatively negative years, the characteristics of Tropical Cyclone in each year, such as a genesis and passage frequency, were investigated. Compared to the relatively negative years, during the relatively positive years, the location of Tropical Cyclone genesis was biased toward South-Eastern region, while the characteristics of the cyclone were more distinct during late season of the year trom September to December than in mid season from June to August. Examining the movement passage through the observation of passage fiequency, there was a significant difference between positive year and negative year in their passages at a 90% confidence level. Moreover, the number of Tropical Cyclone, maximum wind, and life time also showed higher values in positive years than in negative years. These features were confirmed by examining the 850hPa cyclonic flow field, vorticity field, and vertical wind shear field, all of which contribute to the genesis of a Tropical Cyclone.

• 한국지구과학회지
• /
• 제36권3호
• /
• pp.199-209
• /
• 2015

북대서양 자오면 순환(AMOC)은 그린란드 부근에서 고밀도 해수의 침강으로 유도되는데, 이것은 열과 물질을 수송시키기 때문에 기후 시스템의 중요한 요소이다. 이 연구는 전 지구 기후모델 중 하나인 HadGEM2-AO 모델에서 모의된 AMOC의 특징과 장기변동 메커니즘을 분석하였다. AMOC 지수를 이용한 지연 상관 분석을 통해 AMOC의 수십 년 변화는 해양 자체유지 변동으로 간주할 수 있었다. 즉 AMOC의 장기 변화는 남북 수온 경도와 해양 순환의 위상차로 인해 발생하는 불안정성에 의한 것으로 분석되었다. AMOC가 강해지면서 열의 북향 수송에 의해 남북 수온 경도가 작아지고, 따라서 해수의 순환과 열 수송이 줄어드는데, 이와 함께 고위도에서는 냉각이 유도되어 결과적으로 다시 AMOC가 강해지게 된다. 이 메커니즘은 저위도로부터 이류되는 열의 양에 따라 고위도 지역의 밀도 변화가 결정되기 때문에 AMOC의 변동을 염분 유도가 아닌 열적 유도 과정으로 이해할 수 있다.

• 대기
• /
• 제31권1호
• /
• pp.61-71
• /
• 2021

The relationship between the Arctic Oscillation (AO) and surface air temperature (SAT) over Korea is re-examined using the long-term observation and reanalysis datasets for the period of December 1958 to February 2020. Over the entire period, Korean SAT is positively correlated with the AO index with a statistically significant correlation coefficient, greater than 0.4, only in the boreal winter. It is found that this correlation is not static but changes on the decadal time scale. While the 15-year moving correlations are as high as 0.6 in 1980s and 1990s, they are smaller than 0.3 in the other decades. It is revealed that this decadal variation is partly due to the AO structure change over the North Pacific. In the period of 1980s-1990s, the AO-related sea level pressure fluctuation is strong and well defined over the western North Pacific and the related temperature advection effectively changes the winter SAT over Korea. In the other periods, the AO-related circulation anomaly is either weak or mostly confined within the central North Pacific. This result suggests that Korean SAT-AO index relationship, which becomes insignificant in recent decades is highly dependent on mean flow change in the North Pacific.

• 한국해양학회지:바다
• /
• 제24권4호
• /
• pp.509-518
• /
• 2019

다양한 표층 수온 자료를 통해 1979년부터 2018년 기간 동안의 가을철 동해 공간 평균 표층 수온이 태평양 순년 진동과 높은 상관관계를 나타내는 것을 확인하였다. 이 해역에서 제트류의 활동이 가장 강한 200 hPa에서의 바람과 동해 표층 수온의 회귀 분석 결과, 가을철 동해 표층 수온이 상승할 때 제트류의 중심축이 북상하면서 전반적으로 제트류가 약화하는 경향을 보이며, 동해 수온이 하강할 때는 제트류의 중심축이 남하하면서 제트류가 강화되는 경향을 보였다. 이러한 분석 결과는 제트류의 강도 변화와 중심축의 남북 진동이 동해 표층 수온과 태평양 순년 진동의 커플링과 관련되어 있음을 시사한다. 여름철의 약한 제트류와 겨울철 및 이른 봄철의 강한 동아시아 동계계절풍 효과는 동해와 태평양 순년 진동의 커플링이 가을철 외의 다른 계절에 잘 나타나지 않게 하는 이유로 생각해볼 수 있다.

• Ocean Science Journal
• /
• 제41권1호
• /
• pp.1-10
• /
• 2006

Total sea surface temperature (SST) in a coupled GCM is diagnosed by separating the variability into signal variance and noise variance. The signal and the noise is calculated from multi-decadal simulations from the COLA anomaly coupled GCM and the interactive ensemble model by assuming both simulations have a similar signal variance. The interactive ensemble model is a new coupling strategy that is designed to increase signal to noise ratio by using an ensemble of atmospheric realizations coupled to a single ocean model. The procedure for separating the signal and the noise variability presented here does not rely on any ad hoc temporal or spatial filter. Based on these simulations, we find that the signal versus the noise of SST variability in the North Pacific is significantly different from that in the equatorial Pacific. The noise SST variability explains the majority of the total variability in the North Pacific, whereas the signal dominates in the deep tropics. It is also found that the spatial characteristics of the signal and the noise are also distinct in the North Pacific and equatorial Pacific.

• 한국지역지리학회지
• /
• 제16권3호
• /
• pp.216-223
• /
• 2010

본 연구는 북한 혜산시의 1957년에서 2006년 사이의 강수량 데이터를 이용하여 Z지수를 지표로 가뭄과 홍수의 변화 과정을 분석하였다. 50년 동안 혜산시 지역의 가뭄과 홍수 출현 빈도를 연도별 및 사계절별로 구분하여 소파형 기법으로 분석하였다. 분석 결과 혜산시의 연도별 및 사계절별 가뭄과 홍수의 발생빈도는 24% 이상으로서 가뭄과 홍수 재해가 빈번하였다. 다항식접합(Polynomial Fit)과 주기분석 결과, 가을철의 가뭄과 홍수는 수십년간(inter-decadal) 특징이 뚜렷하고 연도별 및 봄, 여름 및 겨울에는 수년간(inter-annual) 특징이 잘 나타난다. 최근에는 가을에 가뭄이 많고 연도별과 봄, 여름 및 겨울에는 홍수가 많았다.

• Ocean and Polar Research
• /
• 제34권1호
• /
• pp.29-35
• /
• 2012

We investigated the interannual relationship between chlorophyll concentrations in the western North Pacific and tropical cyclones (TCs) in the western North Pacific by analyzing data collected for >12 years. Despite the short-term scale (2~3 weeks) in the contribution of tropical cyclones to phytoplankton, the current study revealed that the long-term chlorophyll variability in the western North Pacific is profoundly related to long-term variability in the frequency of TCs. It was also found that the Pacific decadal oscillation (PDO) tends to control such relationships between the 2 bio-physical systems. This result suggests a significant climatic relationship between TC activity and marine phytoplankton, and also suggests the possibility of more accurate estimations of primary production in the western North Pacific.