Ocean Response to Super-Typhoon Haiyan

Present paper studies the ocean response to super-typhoon Haiyan based on satellite and Argo float data. First, we show the satellite-based surface wind and sea surface temperature during super-typhoon Haiyan, and evaluate the widely-used atmospheric and oceanic analysis-or-reanalysis datasets. Second, we investigate the signals of Argo float, and find the daily-sampling Argo floats capture the phenomena of both vertical-mixing-induced mixed-layer extension and nonlocal subsurface upwelling. Accordingly, the comparisons between Argo float and ocean reanalysis reveal that, the typhoon-induced upwelling in the ocean reanalysis needs to be further improved, meanwhile, the salinity profiles prior to typhoon arrival are significantly biased.

Impact of Ocean Domain Definition on Sea Level Budget

Total sea level changes from space radar altimetry are mainly decomposed into two contributions of mass addition and volume expansion of oceans, measured by GRACE space gravimeter and Argo float array, respectively. However, the averages of altimetry, mass, and steric sea level changes have been usually examined over the respective data domains, which are different to one another. Errors arise from this area inconsistency is rarely discussed in the previous studies. Here in this study, an alternative definition of ocean domain is applied for examining sea level budgets, and the results are compared with estimates from different ocean areas. It shows that the impact of area inconsistency is estimated by about 0.3 mm/yr of global trend difference, and averages based on a consistent ocean area yield a closer agreement between altimetry and mass + steric in trend. This contribution would explain some discordances of past sea level budget studies.

Argo Float Reveals Biogeochemical Characteristics Along the Freshwater Gradient Off Western Patagonia

The coastal region off Chilean Patagonia has been poorly studied due to the lack of available observations. Here we analyzed, by the very first time, biogeochemical (BGC) data to elucidate the role that biological and physical processes play on nitrate, oxygen, pH and hydrographic variables, along a salinity gradient off central Patagonia. Argo float profiles covering the upper ocean from December 2015 to July 2019 reveal that offshore waters are characterized by low temperatures and high salinities related to high oxygen and medium-high values of pH and nitrate. As the Argo float drifted onshore, freshwater influences the upper 50–100 m with low salinity and high temperature. Waters under the influence of the continental runoff were characterized by medium-to-high oxygen and pH levels, and the lowest nitrate concentrations. Interestingly, oxygen-deficient waters located beneath the freshwater-modified layer showed the lowest pH and highest nitrate. A comprehensive analysis of the temporal and vertical variability of the oxygen:nitrate ratio, in conjunction with biological-related and physical parameters, indicates that the BGC variability seems to be the result of a synergistic interaction between physical and biological processes, where the stratification sets up the environment and promotes the biological response that, in turn, is auto-regulated by modifying the chemical composition in the freshwater-influenced zone. The arrival of future floats with additional sensors (Chlorophyll/Fluorescence, Photosynthetically Active Radiation, Backscatter, etc.) will add new BGC properties that improve our understanding of the coastal marine response to the increasing freshwater input off western Patagonia in the context of climate change.

Respon Kecepatan Angin Terhadap Variabilitas Klorofil-a di Laut Filipina Dan Maluku Bagian Utara

Suplay massa air di Laut Filipina dan Maluku bagian utara berasal dari Samudera Pasifik. Variabilitas klorofil-a (chl-a) dapat dipengaruhi oleh suplay massa air dari suatu wilayah atau pengaruh interaksi atmosfer dan laut. Penelitian bertujuan untuk menjelaskan pengaruh interaksi atmosfer-laut terhadap variabilitas chl-a secara spasial dan temporal. Data yang digunakan yaitu data citra satelit dengan periode 2003-2019 dan argo float. Hasil menunjukkan chl-a di Laut Filipina selalu berada dibawah 0,1 mg/m3 di sepanjang tahun dan Laut Maluku bagian utara mengalami peningkatan saat musim timur (0,27 mg/m3). Kenaikan chl-a di Laut Maluku bagian utara diikuti dengan kenaikan kecepatan angin (musim timur) yang menyebabkan Ekman Mass Transport (EMT). EMT bergerak kearah timur laut yang membawa massa air menjauhi pantai dan terjadi proses coastal upwelling. Coastal upwelling inilah menjadi faktor utama peningkatan chl-a di Laut Maluku bagian utara. Sebaliknya, kenaikan kecepatan angin di Laut Filipina tidak membangkitkan EMT dan tidak meningkatkan chl-a. Chl-a yang stabil di sepanjang tahun di Laut Filipina membuktikan kecepatan angin kuat tidak terlalu dominan untuk mempengaruhi variabilitas chl-a. Rendahnya chl-a kemungkinan disebakan oleh massa air dari Samudera Pasifik yang dibawa oleh Arus Lintas Indonesia (ARLINDO). Water mass supply in the Philippine Sea and northern Maluku derived from the Pasific Ocean. The variability of chlorophyll-a (chl-a) was affected by the supply of water mass from the area or the impact of air and sea interactions. This study aimed to define the effect of air-sea interaction on the spatial and temporal variability of chl-a. The required data in this study was satellite image data with the period 2003-2019 and argo float. The results showed that chl-a in the Philippine Sea was always below 0.1 mg / m3 throughout the year and the northern Maluku Sea increased during the eastern monsoon (0.27 mg / m3). The increasing of chl-a in the northern Maluku Sea was followed by the increasing of wind speed (east monsoon) which impacted the Ekman Mass Transport (EMT). EMT moved to the northeast carrying the water mass away from the coast and turned up coastal upwelling process. Coastal upwelling was the main factor of chl-a increasing in the North Maluku Sea. In otherwise, wind speed increasing in the Philippine Sea caused vertical mixing (west monsoon) but did not increase chl-a. The stable value of chl-a throughout the years in the Philippine Sea verified that strong wind speeds are not too dominant to affect the variability of chl-a.. The low chl-a was probably caused by the water mass from the Pacific Ocean that carried by Indonesian Through Flow (ARLINDO).

Observed variability of monsoon blooms in the north-central Arabian Sea and its implication on oxygen concentration: A Bio-Argo study

<p><span>The central Arabian Sea (CAS) is productive during both the summer and winter monsoons owing to different physical processes. We analysed four years (2013-2016) record of chlorophyll and dissolved oxygen (DO) concentration from a Bio-Argo float deployed in this region. Though the surface blooms were observed during both the monsoons and sub-surface chlorophyll was also persistently observed, the intensity and duration of the bloom have been decreasing over the past few years. Also, the winter blooms were more prominent compared to the summer bloom in the study region. Our analysis shows that the observed inter-annual variability in the summer bloom can be attributed to the variability in wind speed, oceanic stratification and advection of nutrient rich water from the western Arabian Sea. During both the monsoons, stratification played an important role in reducing the productivity in recent years. We also found that during the winter monsoon, the upwelling Rossby wave propagating from the west coast of India influenced productivity as north as 15ºN. The chlorophyll data from Bio-Argo float shows that the total surface chlorophyll concentration has been decreasing during the study period. Consequently the DO concentration has also been </span><span>decreased</span><span>. </span><span>An increase in the deeper water is speculated to be due to the </span><span> decrease in surface productivity. This is in contradiction to the previous studies on intensification of Arabian Sea OMZ. Also, in the event of recent reports on decreasing trend in productivity in the Arabian Sea, the present study provides new insights on the possible effect of declining productivity on the DO concentration under the climate change regime.</span></p>

Atlantic equatorial deep jets in Argo float data

<p>Equatorial deep jets (EDJ) are strong zonal currents in the deep tropical oceans that alternate in direction with depth and<br>time. In the Atlantic below the thermocline, they are the dominant variability on interannual timescales. They propagate<br>energy upwards and are suggested to impact surface climate variables on interannual timescales. They are also<br>important for the distribution of tracer in the mid-depth tropical ocean, for example by enhanced oxygen ventilation of<br>the eastern deep oxygen minimum zones, both through advection by the EDJ themselves and because the EDJ<br>nonlinearly drive time mean flow. Observations of equatorial deep jets are available but scarce, given the EDJs’ location<br>at depth and their long periodicity of several years. In the last few years, Argo floats have added a significant amount of<br>measurements at intermediate depth. We therefore perfomed a new EDJ scale analysis based on Argo float<br>measurements, the results of which we show here. At 1000 m depth, very weak or no EDJ signals can be detected in the<br>Indian and Pacific Oceans. In the Atlantic, however, the EDJ signal is strong at 1000 m depth, allowing us to obtain<br>good estimates of their frequency, amplitude, phase, zonal wavelength, and meridional structure.</p>