For selected locations in the Atlantic and Pacific Ocean, we compared surface ocean chlorophyll time series extracted from SeaWiFS imagery from 1997-2004 with the results of an ocean coupled circulation and biogeochemical model covering the period 1958-2004. During the 1997-2004 time period, linear trends in model and satellite time series were significantly correlated at most of the 44 sites we studied. Eleven sites were selected for further study, and we used the longer time series of the model to assess whether trends observed during the SeaWiFS period at these 11 sites were unusual in relation to those observed over the longer historical period covered by the model. The results show that the trends observed during the SeaWiFS period were not unusual and fell well within the range in magnitude of linear trends observed in other 8-year periods of model output. This result implies that the SeaWiFS satellite ocean color time series is not yet sufficiently long, on its own, to directly observe any long term changes in phytoplankton chlorophyll that may be occurring in the surface waters of the open ocean as a result of increased ocean stratification linked to global climate changed.

Wave energy resource assessment and trends around Indonesian’s ocean has been carried out by means of analyzing satellite observations. Wave energy flux or wave power can be approximated using parameterized sea states derived from satellite data. Unfortunately, only some surface parameters can be measured from remote sensing satellites, for example for ocean surface waves: significant wave height. Others, like peak wave period and energy period are not available, but can instead be estimated using empirical models. The results have been assessed by meteorological season. The assessment shows clearly where and when the wave power resource is promising around Indonesian’s ocean. The most striking result was found from June to August, in which about 30-40 kW/m (the 90th percentile: 40-60 kW/m, the 99th percentile: 50-70 kW/m) wave power energy on average has been found around south of the Java Island. The significant trends of wave energy at the 95% level have also been studied and it is found that the trends only occurred for the extreme cases, which is the 99th percentile (i.e., highest 1%). Wave power energy could increase up to 150 W/m per year. The significant wave heights and wave power have been compared with the results obtained from global wave model hindcast carried out by wave model WAVEWATCH Ⅲ. The comparisons indicated excellent agreements.

Knowledge of sea surface temperature (SST) behaviour is vital for long-term climate scenarios. This study highlights essential outcomes about the distinguishable and unsurprising warming of the SST along the southern border of the Levantine Basin. The analysis is based on monthly SST data for the period 1948–2018. The southern Levantine Basin has undergone SST increase, during the last 71 years. In this study, a consistent warming trend has been found for the analysed SST data series, with a rate of 0.04°C/a, i.e., 0.4°C/(10 a). From 1975 to 1991 the mean annual SST was 17.1°C, and this increased to be 19.2°C, over the period 2002–2018. Results revealed two opposite trends of variability: a decreasing trend (–0.06°C/a) over the period 1975–1991, and an increasing trend (0.2°C/a) from 2002 to 2018. Over the period 1948–2018, positive mean annual SST anomalies had an average of 1.8°C, and negative anomalies had an average of –1.1°C. The lowest SST total increase was found from January to April, with values about 0.03°C, while the highest warming appeared from June to September. The driving mechanisms behind the SST changes need to be more investigated, to understand the future trends and impacts of climate change in the Levantine Basin.

Chlorophyll a concentration (CHL) is an important proxy of the marine ecological environment and phytoplankton production. Long-term trends in CHL of the South China Sea (SCS) reflect the changes in the ecosystem’s productivity and functionality in the regional carbon cycle. In this study, we applied a previously reconstructed 15-a (2005−2019) CHL product, which has a complete coverage at 4 km and daily resolutions, to analyze the long-term trends of CHL in the SCS. Quantile regression was used to elaborate on the long-term trends of high, median, and low CHL values, as an extended method of conventional linear regression. The results showed downward trends of the SCS CHL for the 75th, 50th, and 25th quantile in the past 15 a, which were −0.004 0 mg/(m³·a) (−1.62% per year), −0.002 3 mg/(m³·a) (−1.10% per year), and −0.001 9 mg/(m³·a) (−1.01% per year). The negative trends in winter (November to March) were more prominent than those in summer (May to September). In terms of spatial distribution, the downward trend was more significant in regions with higher CHL. These led to a reduced standard deviation of CHL over time and space. We further explored the influence of various dynamic factors on CHL trends for the entire SCS and two typical systems (winter Luzon Strait (LZ) and summer Vietnam Upwelling System (SV)) with single-variate linear regression and multivariate Random Forest analysis. The multivariate analysis suggested the CHL trend pattern can be best explained by the trends of wind speed and mixed-layer depth. The divergent importance of controlling factors for LZ and SV can explain the different CHL trends for the two systems. This study expanded our understanding of the long-term changes of CHL in the SCS and provided a reference for investigating changes in the marine ecosystem.

The main purpose of this study is to highlight, on the basis of statistical tests, the significant long-term changes of the Mediterranean Sea level, through the analysis of historical tide gauge records. In this framework, 14 tide gauge monthly series selected from the Permanent Service of the Mean Sea Level (PSMSL) database were used. The search for the presence or not of trends within these series, that have a temporal coverage from 59 to 142 years, was carried out using the Mann-Kendall test and the Sen’s slope estimator. The obtained results show that the Split Rt Marjana series are the only ones which does not exhibit a significant trend. The other 13 series show significant increasing trends. This result seems sufficient to suppose the presence, in the past century, of a new climatic phase on the scale of the Mediterranean basin, where the rising sea level is one of the consequences.

The concentration and composition of nutrients, such as N, P, and Si, respond to biogeochemical processes and in turn, impact the phytoplanktons’ community structure and primary production. In this study, historical data was systematically analyzed to identify long-term variations in nutrient trends, red tide frequency, phytoplankton community abundance, and dominant species succession in the southern Yellow Sea (SYS). Results showed that N/P concentration ratios dramatically increased as a function of increasing dissolved inorganic nitrogen concentrations, and Si/N concentration ratios were generally larger than 1, indicating that N limitation morphed to P limitation and potentially to Si limitation, which impacted the phytoplankton community. Furthermore, inter-annual trends over the past 50 years show that phytoplankton community abundance has been higher in spring and summer, relative to autumn and winter. Moreover, with respect to red tide frequency, diatom abundance gradually decreased, while that of dinoflagellates gradually increased. Dominant species succession showed that the phytoplankton community exhibited an evident tendency to transform from diatoms to dinoflagellates. These research results clearly depict the presence of an important correlation between the phytoplankton community and nutrient structure in the SYS.

本文使用高分辨率卫星数据研究了2003-2017年南海海表温度及海表温度锋面的变化趋势。研究表明海盆平均的SST增温趋势为0.031℃/年，并且越南东南海域增温最为显著。南海夏季和冬季海盆平均的SST增温趋势基本一致，然而SST增温的空间分布却有明显的季节性差异。夏季吕宋海峡西侧增温幅度最大，高于0.06℃/年。冬季最大的增温则出现在越南东南海域。研究发现大陆沿岸的海表温度锋面强度有增加趋势，这一变化趋势与局地风应力增强有关。南海SST异常和海表温度锋面异常与Niño3.4指数具有较好的相关性，表明南海SST以及海表温度锋面的变化趋势会受到厄尔尼诺过程的影响，具有大尺度特征。

基于几种客观分析数据集和两个再分析数据集，本文研究了南海上层海温的年代际变化特征。在20世纪90年代后期，南海海表面温度由升温趋势转变为降温趋势。通过热收支分析，研究发现1984至1999年期间南海上混合层的升温趋势主要是由水平热输送和向上的长波辐射减少导致的；由于感热通量和潜热通量的增多，净热通量对升温趋势起抑制作用。另一方面，引起2000至2009年期间上混合层降温趋势的主要因素是净热通量，其中辐射通量的变化起主要作用。本文探究出一个导致上述现象可能机制：北太平洋海表面气压的异常变化会影响南海上层盛行风，进而通过改变水平热输送项和热通量项改变南海SST的变化趋势。

The variability in global oceanic evaporation data sets was examined for the period 1988-2000.These data sets are satellite estimates based on bulk aerodynamic formulations and include the NASA/Goddard Space Flight Center Satellite-based Surface Turbulent Flux version 2 (GSSTF2), the Japanese-ocean flux using remote sensing observations (J-OFURO), and the Hamburg Ocean-Atmosphere Parameters and Fluxes from Satellite version 2 (HOAPS2).The National Center for Environmental Prediction (NCEP) reanalysis is also included for comparison.An increase in global average surface latent heat flux (SLHF) can be observed in all the data sets.Empirical mode decomposition (EMD) shows long-term increases that started around 1990 for all remote sensing data sets.The effect of Mt.Pinatubo eruption in 1991 is clearly evident in HOAPS2 but is independent of the long-term increase.Linear regression analyses show increases of 9.4%, 13.0%, 7.3%, and 3.9% for GSSTF2, J-OFURO, HOAPS2 and NCEP, for the periods of the data sets.Empirical orthogonal function (EOF) analyses show that the pattern of the first EOF of all data sets is consistent with a decadal variation associated with the enhancement of the tropical Hadley circulation, which is supported by other satellite observations.The second EOF of all four data sets is an ENSO mode, and the correlations between their time series and an SOI are 0.74, 0.71, 0.59, and 0.61 for GSSTF2, J-OFURO, HOAPS2, and NCEP in that order.When the Hadley modes are removed from the remote sensing data, the residue global increases are reduced to 2.2%, 7.3%, and <1% for GSSTF2, J-OFURO and HOAPS, respectively.If the ENSO mode is used as a calibration standard for the data sets, the Hadley mode is at least comparable to, if not larger than, the ENSO mode during our study period.

An obvious trend shift in the annual mean and winter mixed layer depth (MLD) in the Antarctic Circumpolar Current (ACC) region was detected during the 1960–2021 period. Shallowing trends stopped in mid-1980s, followed by a period of weak trends. The MLD deepening trend difference between the two periods were mainly distributed in the western areas in the Drake Passage, the areas north to Victoria Land and Wilkes Land, and the central parts of the South Indian sector. The newly formed ocean current shear due to the meridional shift of the ACC flow axis between the two periods is the dominant driver for the MLD trends shift distributed in the western areas in the Drake Passage and the central parts of the South Indian sector. The saltier trends in the regions north to Victoria Land and Wilkes Land could be responsible for the strengthening mixing processes in this region.