Article
Optics
Siqi Zhang, Peng Chen
Summary: This study observed the subsurface phytoplankton vertical structure in the South China Sea (SCS) during the onset of the summer monsoon using lidar for the first time. A hybrid retrieval method based on lidar data was proposed to determine the vertical structure of seawater chlorophyll-a concentrations. Comparison with ocean color data revealed spatial and diurnal variations in the subsurface chlorophyll-a maximum layer (SCML). The changes in SCML depth in the SCS were attributed to variations in light availability and nutrient supply. The preliminary findings demonstrated the potential of lidar measurements in understanding submesoscale oceanic dynamics mechanisms.
Article
Oceanography
Cara Wilson
Summary: The study investigated the development of summer blooms of chlorophyll in the oligotrophic North Pacific Ocean, specifically near Hawaii, and found evidence of episodic injections of subsurface nutrients stimulating these blooms. Data from Biogeochemical-Argo floats revealed that during injection events, perturbations to the vertical nitrate distribution extended down to 300 m depth and lasted up to 3.5 months, spanning hundreds of kilometers. Additionally, the injection events within cyclonic eddies were followed by a surface increase in chlorophyll in the surrounding area as observed in satellite data.
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
(2021)
Article
Oceanography
Peter G. G. Strutton, Thomas W. W. Trull, Helen E. E. Phillips, Earl R. R. Duran, Sylvia Pump
Summary: Eddies in the southeast Indian Ocean play a role in modulating open ocean productivity, with their impact depending on their source and evolution. These eddies can stimulate and sustain phytoplankton, allowing their effects to persist over long distances. Measurements from autonomous floats show that chlorophyll and particulate organic carbon become concentrated at the base of the mixed layer as eddies are transported westward. The subsurface biomass maxima in both anticyclonic and cyclonic eddies remain active over several months, suggesting a mechanism for long-distance transfer of eddy plankton communities not captured by satellite remote sensing.
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
(2023)
Article
Geosciences, Multidisciplinary
Jiaoyang Su, Peter G. Strutton, Christina Schallenberg
Summary: Mesoscale eddies in the Southern Ocean play a key role in redistributing momentum, potential vorticity, heat, and salt, and also have an impact on subsurface biological structures. Eddy pumping, eddy-induced Ekman pumping, and deep vertical mixing are the main mechanisms sustaining high chlorophyll in eddies.
JOURNAL OF MARINE SYSTEMS
(2021)
Article
Environmental Sciences
Ya-nan Ding, Fei Yu, Qiang Ren, Feng Nan, Ran Wang, Yansong Liu, Ying Tang
Summary: The physical and biogeochemical properties within the subsurface anticyclonic eddy (SSAE) and in the surrounding water are distinct due to the unique physical processes of mesoscale eddies. The central potential density structure of a long-standing SSAE exhibits distinct seasonal variations, which may be related to the subduction of low-potential vorticity mode water. Chlorophyll (CHL) and dissolved oxygen (DO) are significantly enhanced in the core of the SSAE, while elevated CHL and DO levels and reduced nitrate levels are observed along the periphery of the eddy. The strength of the SSAE is enhanced due to the eddy kinetic energy provided by the positive baroclinic conversion rate during the Kuroshio path transition period.
FRONTIERS IN MARINE SCIENCE
(2022)
Article
Environmental Sciences
Wenlong Xu, Guifen Wang, Xuhua Cheng, Xiaogang Xing, Jianhuang Qin, Guidi Zhou, Long Jiang, Bingzhang Chen
Summary: In this study, the influence of mesoscale eddies on the subsurface chlorophyll maximum (SCM) layers in the South China Sea was examined using a coupled model. The results showed that eddies play a significant role in shaping the depth, thickness, and magnitude of SCM layers. The effects of eddies on SCM layers are most pronounced near the center of eddies and also influence the phytoplankton community structure.
JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
(2023)
Article
Oceanography
D. Ito, T. Kodama, Y. Shimizu, T. Setou, K. Hidaka, D. Ambe, S. Sogawa
Summary: The study investigates the contribution of oceanic front and its strengthening to subsurface chlorophyll a (CHL) concentration near the Kuroshio. It is found that frontogenesis leads to the shoaling of the nitracline and an increase in subsurface CHL concentration. Additionally, the study demonstrates that the strengthening of fronts can be estimated using satellite-derived data to determine the distribution of CHL concentration.
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
(2023)
Review
Oceanography
Qingyou He, Dennis J. McGillicuddy Jr, Xiaogang Xing, Shuqun Cai, Weikang Zhan, Yinghui He, Jiexin Xu, Haigang Zhan
Summary: This study reveals a decoupling between subsurface phytoplankton biomass and surface chlorophyll in cyclonic and anticyclonic eddies in the South Indian Ocean. The cyclonic eddy exhibits a subsurface phytoplankton bloom with a decrease in surface chlorophyll, while the anticyclonic eddy shows homogeneous phytoplankton biomass with a deep mixed layer. This phenomenon is confirmed by global biogeochemical-Argo measurements, highlighting the importance of considering subsurface phytoplankton abundance and productivity in satellite measurements.
PROGRESS IN OCEANOGRAPHY
(2023)
Article
Oceanography
L. W. Juranek, B. Hales, N. L. Beaird, M. A. Goni, E. Shroyer, J. G. Allen, A. E. White
Summary: This study finds that middepth waters in Arctic marginal seas play a significant role in regional productivity, as indicated by the presence of subsurface chlorophyll maxima (SCM) and large oxygen excess. The SCM coincides with a compensation point for balanced growth and loss, and is associated with turbulence minima and increased light attenuation. The vertical and spatial patterns of SCM and productivity are influenced by stratification, turbulence, light availability, and seasonal water mass formation.
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
(2023)
Article
Microbiology
Peiqing He, Huan Wang, Jie Shi, Ming Xin, Weimin Wang, Linping Xie, Qinsheng Wei, Mu Huang, Xuefa Shi, Yaqin Fan, Hao Chen
Summary: Oceanic oxygen levels are decreasing due to global climate change, and this study investigates the microbial response to dissolved oxygen in the tropical Pacific Ocean. The results show that various factors, including nitrate, temperature, pH, silicate, phosphate, chlorophyll a, dissolved oxygen, and salinity, significantly influence the microbial community composition. Specific microbial ecotypes were observed to be associated with distinct vertical niches. Additionally, it was found that low dissolved oxygen favors the growth of Thaumarchaeota and the production of nitrate.
Article
Oceanography
S. Itoh, H. Kaneko, S. Kouketsu, T. Okunishi, E. Tsutsumi, H. Ogawa, I. Yasuda
Summary: This study conducted direct microstructure measurements in the upper 300 m of the open Pacific during summer, revealing different diffusivity patterns in various geographical regions. Improving estimations of material transport based on diffusivity distributions will contribute to better understanding biogeochemical cycles in the stratified upper ocean.
JOURNAL OF OCEANOGRAPHY
(2021)
Article
Limnology
Yoshimi M. Rii, Logan M. Peoples, David M. Karl, Matthew J. Church
Summary: The study examined the variability and resilience of the picoeukaryotic community in the euphotic zone based on time-series observations in the North Pacific Subtropical Gyre. Results suggest that the picoeukaryotic communities in this habitat are resilient on timescales of days to weeks in response to physical disturbances, highlighting the need for spatially and temporally resolved assessment of community response and resilience to different scales of disturbances. The study emphasizes the value of examining recent physical forcing of the upper ocean for understanding the influences of physical habitat alterations on the plankton community.
LIMNOLOGY AND OCEANOGRAPHY
(2022)
Article
Multidisciplinary Sciences
Taketoshi Kodama, Tsuyoshi Watanabe, Yukiko Taniuchi, Akira Kuwata, Daisuke Hasegawa
Summary: Primary productivity is changing in the oligotrophic North Pacific Subtropical Gyre (NPSG), prompting a re-evaluation of the micro-size plankton community structure. Dinoflagellates were the most abundant micro-size plankton, with other classes not always detected. Generalized additive models and principal coordination analyses indicated heterogeneity in habitats and assemblages, with unique communities observed at different depths. Diazotrophic Cyanophyceae may contribute to this heterogeneity in the western NPSG.
Article
Oceanography
Hitoshi Kaneko, Ichiro Yasuda, Sachihiko Itoh, Shin-ichi Ito
Summary: Vertical turbulent nitrate fluxes were estimated in the western North Pacific during the summer of 2008. Subsurface fluxes showed increasing trend with nitrate gradient in different water regions. Enhancement of fluxes was observed in the subarctic area and the frontal areas, with different mechanisms contributing to the turbulence.
JOURNAL OF OCEANOGRAPHY
(2021)
Article
Environmental Sciences
Sandra Tippenhauer, Markus Janout, Manita Chouksey, Sinhue Torres-Valdes, Allison Fong, Thorben Wulff
Summary: The study conducted a coordinated frontal survey in Fram Strait in summer 2016 using an AUV along with shipboard and zodiac-based hydrographic measurements. They observed a front between warm Atlantic Water and cold Polar Water, and identified a high chlorophyll subsurface patch potentially sustained by upward nitrate fluxes. The observations highlight the complex hydrographic and biogeochemical structure in the region, emphasizing the importance of submesoscale dynamics in driving subsurface phytoplankton blooms.
FRONTIERS IN MARINE SCIENCE
(2021)
Editorial Material
Oceanography
Tal Ezer, Fanghua Xu, Zhiyu Liu, Emil Stanev, Shanlin Wang, Jun Wei
Article
Limnology
Kuanbo Zhou, Claudia R. Benitez-Nelson, Jie Huang, Peng Xiu, Zhenyu Sun, Minhan Dai
Summary: Mesoscale eddies in the North Pacific Subtropical Gyre were found to enhance nutrient injection into the photic zone, affecting the magnitude and composition of particle export to depth. Biogenic silica fluxes were significantly higher at both the cores and edges of cyclonic eddies, with peak values occurring during the mature stage. During the bloom season, all elemental fluxes were reduced in cyclonic eddies compared to non-eddy references.
LIMNOLOGY AND OCEANOGRAPHY
(2021)
Article
Oceanography
Jie Huang, Robert S. Pickart, Frank Bahr, Leah T. McRaven, Fanghua Xu
Summary: The study investigates the ventilation of overflow water feeding Denmark Strait in the western Iceland and Greenland Seas. Warm, saline Atlantic-origin Overflow Water (AtOW) and cold, fresh Arctic-origin Overflow Water (ArOW) are the two main classes of overflow water studied. The research focuses on the modification of water properties in the East Greenland Current and the interior of the Iceland and Greenland Seas, as well as the impact of a cold-air outbreak and atmospheric forcing on the ventilation of overflow water components.
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
(2021)
Article
Physics, Multidisciplinary
Fei Gao, Fang-Hua Xu, Zheng-Lin Li
Summary: This paper investigates the effects of mesoscale eddies on spatial coherence in the subsurface of deep water. It is found that cold/warm mesoscale eddies affect spatial coherence by changing the locations and width of the convergence zone. In the shadow zone, the horizontal and vertical correlation radius increase with range and decrease with depth, and they are increased by warm eddies and decreased by cold eddies, mainly due to variations in the multipath structure.
Article
Geosciences, Multidisciplinary
Xueyang Zhang, Fanghua Xu, Jishi Zhang, Yanluan Lin
Summary: Tropical cyclones are an important source of turbulent mixing in the low latitude upper ocean, resulting in sea surface cooling and subsurface warming. A new estimate shows a decreasing trend in both sea surface cooling and upper ocean diffusivity caused by tropical cyclones globally, which is influenced by global warming and changes in tropical cyclone characteristics.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Oceanography
Hong Li, Fanghua Xu, Guihua Wang, Ruizi Shi
Summary: This study aims to investigate the tilting of mesoscale eddies observed in oceans through a series of ideal numerical experiments. The simulated eddies display a nonlinear behavior near the surface and gradually transform into Rossby waves with depth, consistent with previous observations. The tilting of eddies occurs in nearly every experiment and is associated with the decrease in planetary rotation and the increase in ocean stratification. The results suggest that the eddy tilt is influenced by the depth-dependent propagation speed of eddies and warrant further investigation.
DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS
(2023)
Article
Meteorology & Atmospheric Sciences
Ian A. A. Renfrew, Jie Huang, Stefanie Semper, Christopher Barrell, Annick Terpstra, Robert S. S. Pickart, Kjetil Vage, Andrew D. D. Elvidge, Thomas Spengler, Anna-Marie Strehl, Alexandra Weiss
Summary: Marine cold-air outbreaks (CAOs) refer to the sudden attack of cold air towards the equator over the ocean, causing a significant loss of oceanic heat in the subpolar seas of the North Atlantic during winter. This study presents coupled observations of the atmosphere and ocean during a CAO event in the subpolar North Atlantic region in 2018. The observations reveal substantial changes in temperature, humidity, and wind throughout the atmospheric boundary layer during the CAO event. The ocean's response to the CAO is dependent on location, with cooling and deepening of the mixed layer in the Iceland Sea interior and warming in the boundary current region.
QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY
(2023)
Article
Multidisciplinary Sciences
Jie Huang, Robert S. Pickart, Zhuomin Chen, Rui Xin Huang
Summary: This study reveals the different roles of air-sea heat exchange in the transformation of Atlantic Water along the two northward-flowing warm currents in the Nordic Seas, which needs to be considered to understand high-latitude response to climate change.
NATURE COMMUNICATIONS
(2023)
Article
Environmental Sciences
Shuyi Zhou, Fanghua Xu, Ruizi Shi
Summary: Accurate calculation of whitecap fraction is important for estimating air-sea momentum flux, heat flux, and sea-salt aerosol flux in Earth system models. Past parameterizations mostly used wind speed as the sole factor, which led to difficulties in explaining the variability of whitecap fraction. In this study, a new multivariate parameterization using deep neural network was constructed, which reduced computational error by 15% compared with a recent parameterization by Albert et al. The importance of input variables such as significant wave height and sea surface temperature in the parameterization of whitecap fraction was ranked through a permutation test.
Article
Oceanography
Hong Li, Fanghua Xu, Guihua Wang
Summary: Oceanic mesoscale eddies are prevalently vertically tilted, with anticyclonic eddies tilted westward and poleward, and cyclonic eddies tilted westward and equatorward. The horizontal tilting distance of eddies is significantly correlated with the Burger number, indicating a strong constraint of Earth's rotation and ocean stratification on eddy vertical tilt. The maximum vertical velocity in tilted circular eddies is at least one order of magnitude larger than that in non-tilted circular eddies, which improves the estimates of eddy-induced vertical motion, ventilation, and heat/salt and biogeochemical responses.
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
(2022)
Article
Oceanography
Hong Li, Fanghua Xu, Guihua Wang, Ruizi Shi
Summary: Vertical tilt of mesoscale eddies has been frequently observed in world oceans. This study finds that the tilt increases with time, indicating a change in translation speed with depth. The classic linear Rossby wave theory fails to explain the tilt, leading to the development of a new dispersion relation that predicts the observed tilt structure effectively. This new theory shows promise in predicting the vertical tilt of mesoscale eddies in oceans.
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
(2022)
Article
Environmental Sciences
Ruizi Shi, Qinya Zhang, Fanghua Xu, Xueyang Zhang, Yanluan Lin, Jishi Zhang
Summary: Tropical cyclones have had a significant decline in their ability to absorb ocean heat in recent decades, resulting in a reduction of approximately 15% in poleward heat transport, particularly in the Northwest Pacific. This decline is consistent with the strengthening of ocean stratification, shallower mixed layer depth, and smaller cold wake size. Additionally, the decline in ocean heat uptake may offset about 28% of upper ocean warming in the subtropical Northwest Pacific.
ENVIRONMENTAL RESEARCH LETTERS
(2023)
Article
Oceanography
Jie Huang, Robert S. Pickart, Nicholas Foukal, Michael A. Spall, Peigen Lin
Summary: Barrow Canyon in the northeast Chukchi Sea is a critical choke point for Pacific-origin water entering the interior Arctic. Two shipboard surveys in 2018 revealed that the distribution of Pacific water differed between summer and late fall, which can be attributed to differences in wind forcing. A cyclone-like circulation in the canyon was observed during both surveys.
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
(2023)
Article
Geosciences, Multidisciplinary
Ruizi Shi, Fanghua Xu, Li Liu, Zheng Fan, Hao Yu, Hong Li, Xiang Li, Yunfei Zhang
Summary: This article describes the implementation of a coupling between a global forecast model and a wave model and investigates the effects of ocean surface waves on the air-sea interface. Through experiments and comparisons with observational data, it is found that the interaction between waves and the atmosphere in the new framework significantly improves the prediction of various parameters related to sea surface temperature, air temperature, mixed layer depth, wind speed, and wave height.
GEOSCIENTIFIC MODEL DEVELOPMENT
(2022)
Article
Oceanography
Wei Zhou, Jinghui Li, Fanghua Xu, Yeqiang Shu, Yang Feng
Summary: The study applied an ensemble optimal interpolation (EnOI) data assimilation method to investigate the impact of ocean data assimilations on seasonal forecasts in an idealized twin experiment framework. It was found that joint assimilation of all variables significantly improved prediction accuracy, with a crucial role of assimilating T/S profiles in reducing subsurface deficiencies. Surface data assimilation was more important at higher latitudes, particularly near the western boundary currents.
ACTA OCEANOLOGICA SINICA
(2021)