Drop In Sea Surface Temperature Research Articles

Tide‐Induced Periodic Sea Surface Temperature Drops in the Coral Reef Area of Nanwan Bay, Southern Taiwan

AbstractTidal current‐induced cyclonic eddies cause cold‐water upwelling and periodic sea surface temperature (SST) drops around the coral reef area in Nanwan Bay, which is located at the southern tip of Taiwan. This study used Himawari‐8 satellite data and tide gauge and coastal ocean dynamics application radar (CODAR) data to analyze the characteristics of the SST drops and cyclonic eddy propagation and used an oceanic general circulation model (OGCM) to simulate the tidal current flowing process. According to the CODAR data analysis, the mixed primary semidiurnal tide had an average current velocity of 0.3–0.4 m s−1 throughout the bay, and the average life cycle of a cyclonic eddy is 6.6 hr, with a propagation speed of 0.35 m s−1. The SST drop during the spring tide period was greater than that during the neap tide period, and the SST dropped in both summer and winter. The average daily SST drop in the summer reached 2 °C with a maximum observed value of 4.7 °C, and the SST drop rate was 0.3–0.5 °C hr−1. The annual mean chlorophyll‐a concentration was 0.25 mg m−3. This study explored the special properties of the Nanwan Bay coral reef area from the perspective of ocean physics to allow ecologists to facilitate the implementation of long‐term conservation and monitoring programs.

Upwelling spike and marked SST drop after the arrival of cyclone Dorian to the Atlantic Canadian coast

In intertidal environments, temperature changes at hourly scales are ecologically relevant because of the physiological stress that organisms must endure as a result. Tides constitute the main source of such changes, as low tides periodically expose intertidal habitats to aerial conditions, which can exhibit extreme high and low temperatures in summer and winter, respectively. This study identifies a source of strong hourly thermal variation that acts upon seawater temperature. Hours after the arrival of cyclone Dorian to the Atlantic Canadian coast in September 2019, intertidal loggers revealed that sea surface temperature (SST) decreased by 10–12 °C. Online data indicated that neither tidal amplitude nor air temperature were responsible for this marked SST drop. Conversely, data on wind speed and direction strongly suggest that a pronounced spike in coastal upwelling caused by this cyclone drove the sharp drop in intertidal SST. Bakun's upwelling index, for instance, peaked at 689 m3 s−1 (100 m of coastline)−1 a few hours after Dorian's landfall. It remains to be seen how this marked SST drop may have affected intertidal organisms, as they were then acclimated to summer conditions. As the frequency and intensity of cyclones are predicted to increase with climate change in temperate latitudes, cyclone-related intertidal thermal ecology might deserve further attention.

An abrupt cooling event recorded around 73 kyr in western South Atlantic

This paper presents the record of sea surface temperature and planktonic foraminifera cold species for the last 130 kyr of a deep sea marine piston core (GL-854) from western South Atlantic. Our data shows a prominent and consistent feature around 73 kyr when an abrupt drop in sea surface temperature, both artificial neural network and oxygen isotope-based, was recorded. Additionally, our oxygen isotope curve presents a positive excursion and two cold-water planktonic foraminifera (Globoconella inflata and Neogloboquadrina incompta) remarkably increased their abundances. The benthic oxygen isotope record did not indicate any change while planktonic indicators were intensely disturbed. This cooling episode should be explained by a strong and abrupt mechanism able to promptly affect the surface ocean but not the deep ocean. It seems to be one of the coldest intervals during the last 130 kyr. Here, we discuss some hypothesis for this abrupt cooling recorded in the South Atlantic, including the speculative climatic impact of Toba super-eruption.

Satellite Evidence of Upper Ocean Responses to Cyclone Nilofar

ABSTRACTCyclone Nilofar was the third-strongest cyclone in the Arabian Sea. It was a category 4 cyclone that arrived in last week of October 2014. It lingered in the Arabian Sea for 10 days and caused a significant phytoplankton bloom that was detected by satellite observation. In this study, the authors investigated the ocean biological and physical responses to cyclone Nilofar using chlorophyll a (chl a) concentration, sea surface temperature (SST), sea surface height anomaly (SSHA), sea surface wind measurements derived from different satellites, and in situ data. The maximum chl a concentration (>3.34 mg m−3) increased about 28 times in the Arabian Sea after the passage of the cyclone in comparison with the chl a concentration (0.12–0.92 mg m−3) before the passage of cyclone. Using the relationship of wind stress curl and upwelling, the authors found that during the cyclone the speed of upwelling increased more than 18 times compared with the speed in the period before the cyclone. Moreover, the mixed layer deepened by about 40 m. These findings reveal that the enhancement of chl a concentration was triggered by strong vertical mixing and upwelling. Along the track of the cyclone, the maximum sea surface cooling (4°–5°C) took place in the Arabian Sea along segments A–B and D–F where the translation speed of the cyclone was only 0.9–1.3 m s−1, and the mixed-layer depth was about 10 m in the pre-cyclone period. However, the drop in SST along segment C–D was only 1°–2°C, whereas in the pre-cyclone period the translation speed of the cyclone was 3.1–4.4 m s−1, and the mixed-layer depth was about 25 m in. So, the extent of the SST drop was probably due to the translation speed of the cyclone and the depth of the mixed layer. In addition, the region with the largest decline in SSHA can indicate the location of maximum cooling.

New Possibilities In The Study Of Coastal Upwellings In The Southeastern Baltic Sea With Using Thermistor Chain

The article gives an analysis of a unique data of the thermistor chain, which installed on the D-6 oil platform in the coastal zone of the Baltic Sea. In total 10 temperature sensors were installed at different depths with a recording interval of 1 min, the depth at the installation site was 29 m. Based on satellite data, ship measurements and thermistor chain observation the characteristics and dynamics of the sharp decrease in water temperature which registered in the south-eastern Baltic Sea (Gdansk Bay area), during June 5-12, 2016 are analyzed. The temperature decreasing caused by the simultaneous action of at least two factors: wind-driven Ekman upwelling and advection of cold water. Scales of temporal and spatial variability of water temperature in a coastal zone of the south-eastern Baltic Sea near the coast of the Kaliningrad region are described. This event led to the considerable SST (sea sur face temperature) drop by more than 8 °C for two days. The rate of reduction of its temperature during certain upwelling periods can reach 0.3-0.4 o С per hour, but the maximum warming rate between phases varies from 0.25 to 0.28 o С per hour. This dramatically changed the conditions of the thermal balance of the sea sur face. The width of the upwelling, as seen in the SST data, was about 25 km. Satellite data were supplemented with data of a thermistor chain and C TD measurements. The high correlation between water temperature variability and changes in wind parameters: when the wind speed has decreased and its direction has changed, the response of the vertical thermal structure has occurred very quickly, sometimes within 1 hour. Thermistor chain data allow to evaluate the vertical temperature distribution and get more detailed analysis of temporal variability and short pulsations of upwelling.

Field investigations of coastal sea surface temperature drop after typhoon passages

Abstract. Sea surface temperature (SST) variability affects marine ecosystems, fisheries, ocean primary productivity and human activities and is the primary influence on typhoon intensity. SST drops of a few degrees in the open ocean after typhoon passages have been widely documented; however, few studies have focused on coastal SST variability. The purpose of this study is to determine typhoon-induced SST drops in the near-coastal area (within 1 km of the coast) and understand the possible mechanism. The results of this study were based on extensive field data analysis. Significant SST drop phenomena were observed at the Longdong Buoy in northeastern Taiwan during 43 typhoons over the past 20 years (1998–2017). The mean SST drop (ΔSST) after a typhoon passage was 6.1 ∘C, and the maximum drop was 12.5 ∘C (Typhoon Fungwong in 2008). The magnitude of the SST drop was larger than most of the observations in the open ocean. The mean duration of the SST drop was 24 h, and on average, 26.1 h were required for the SST to recover to the original temperature. The coastal SST drops at Longdong were correlated with the moving tracks of typhoons. When a typhoon passes south of Longdong, the strong and persistent longshore winds induce coastal upwelling and pump cold water up to the surface, which is the dominant cause of the SST drops along the coast. In this study, it was determined that cold water mainly intruded from the Kuroshio subsurface into the Okinawa Trough, which is approximately 50 km from the observation site. The magnitude of coastal SST drops depends on the area of overlap between typhoons generating strong winds and the Kuroshio. The dataset used in this study can be accessed from https://doi.org/10.1594/PANGAEA.895002.

WSPÓŁCZESNE OCHŁODZENIE REJONU SZETLANDÓW POŁUDNIOWYCH I PÓŁNOCNO-ZACHODNICH KRAŃCÓW PÓŁWYSPU ANTARKTYCZNEGO

Artykuł omawia zmiany warunków hydro-klimatycznych w rejonie Szetlandów Południowych i NW części Półwyspu Antarktycznego w latach 1979-2016. Są one istotne dla oceny zmian zachodzących w ekosystemach morskich i nadmorskich. Ogólną ich cechą jest przejście od fazy silnego ocieplenia do fazy ochładzania, co nastąpiło około 2000 r. Przedstawiono zmiany rocznej i sezonowej temperatury powietrza, temperatury powierzchni morza (SST) oraz powierzchni lodów morskich na morzach Bellingshausena i Weddella. Najsilniejszy spadek temperatury powietrza zaznacza się w okresie antarktycznego lata, na wszystkich stacjach zaznacza się spadek temperatury rocznej. Spadek SST następuje we wszystkich miesiącach roku, jest on wysoce istotny. Najsilniejszy spadek SST następuje również latem. Roczna powierzchnia zlodzona na Morzu Weddella systematycznie rośnie, zaznacza się szczególnie szybki przyrost powierzchni lodów w okresie luty-marzec. Roczna powierzchnia lodów na Morzu Bellingshausena po 2000 r. przestała spadać i zaznacza się w jej przebiegu słaby trend dodatni.

Remote Sensing of Coastal Upwelling in the South-Eastern Baltic Sea: Statistical Properties and Implications for the Coastal Environment

A detailed study of wind-induced coastal upwelling (CU) in the south-eastern Baltic Sea is presented based on an analysis of multi-mission satellite data. Analysis of moderate resolution imaging spectroradiometer (MODIS) sea surface temperature (SST) maps acquired between April and September of 2000–2015 allowed for the identification of 69 CU events. The Ekman-based upwelling index (UI) was applied to evaluate the effectiveness of the satellite measurements for upwelling detection. It was found that satellite data enable the identification of 87% of UI-based upwelling events during May–August, hence, serving as an effective tool for CU detection in the Baltic Sea under relatively cloud-free summer conditions. It was also shown that upwelling-induced SST drops, and its spatial properties are larger than previously registered. During extreme upwelling events, an SST drop might reach 14 °C, covering a total area of nearly 16,000 km2. The evolution of an upwelling front during such intensive events is accompanied by the generation of transverse filaments extending up to 70 km offshore. An analysis of the satellite optical data shows a clear decline in the chlorophyll-a concentration in the coastal zone and in the shallow Curonian Lagoon, where it drops down by an order of magnitude. It was also shown that a cold upwelling front alters the stratification in the atmospheric boundary layer, leading to a sudden drop of air temperature and near-surface winds.

Extraordinary cold episodes during the mid-Holocene in the Yangtze delta: Interruption of the earliest rice cultivating civilization

In the estuary region of the Yangtze River (China), the oldest Neolithic civilization based on paddy rice cultivation flourished in the mid-Holocene (7.5–4.2 cal. kyr BP). However, although it is known that this Neolithic civilization collapsed at around 4.2 cal. kyr BP, the reason behind the collapse remains controversial. A sedimentary core (MD06-3040) collected from the inner shelf of the East China Sea, off the southeast coast of China, provides an excellent insight into estimate the Holocene regional paleoenvironment, including the alkenone based sea surface temperature (SST), atmospheric temperature (AT), and paleoproductivity. Extraordinarily severe abrupt cold episodes (i.e., 3–4 °C drop in SST) occurred frequently in the Yangtze delta region during 4.4–3.8 cal. kyr BP. These episodes could have been related to the global climatic transition called the “4.2 ka event”, when the East Asian monsoon hydrological regime might have been altered. The cold episodes could be sufficiently severe to damage rice cultivation and their occurrence constitutes a plausible explanation for the demise of the Yangtze Neolithic civilization.

Daily movement patterns of red snapper (Lutjanus campechanus) on a large artificial reef

Red snapper (Lutjanus campechanus) are at the center of many artificial reef efforts in the Gulf of Mexico. To elucidate red snapper use of artificial structure for fisheries management, their fine-scale movements need to be examined further. Much effort until now has focused on examining movement patterns of red snapper at isolated reef structures, yet fish may behave differently on reefs covering larger areas. To address this, 15 red snapper were internally tagged with V9P transmitter tags and tracked with VR2W receivers for three months at a large artificial reef (PS-1047, 0.8 km2, bottom depth range 21 m–23 m) that was comprised of a tugboat and over 4800 concrete culverts deployed randomly around the area. Ten receivers were arranged on the reef to calculate center of activity and depth for each fish every 20 min. Kernel densities (KDE) were calculated at 95% (77,905.04 ± 1843.27 m2) and 50% (16,797.25 ± 413.02 m2) to address home range and core area use, respectively. There were differences in KDE and depth per day, and depth exhibited diel patterns. There were significant decreases in KDE and increases in depth use after a drastic drop in sea surface temperature. Overall fish use of PS-1047 resulted in two key areas (50% KDE), which comprised of two main groups of fish without overlap and highlighted two different structure areas (tugboat vs. culvert). Home range and core area values were more than 4 times larger than reported in other studies on red snapper.

Upper Ocean and Subsurface Variability in the Bay of Bengal During Cyclone ROANU: A Synergistic View Using In Situ and Satellite Observations

In this study, the upper ocean and subsurface variability during the different phases of the cyclonic storm ROANU along the western Bay of Bengal (BoB) in May 2016 are investigated by using the moored buoys, Argos, HF radar and satellite datasets in the proximity of the cyclone track. The moored buoy observations recorded a decrease of sea surface temperature (SST) by ~ 1 °C all over the track, whereas increase in salinity by ~ 1.5 PSU was detected along with the highest wind speed of 16 m s−1, pressure drop of 14 hPa and air temperature drop of 4 °C. The cooling at the cyclone centers from the satellite data indicated higher (lower) SST drops when translation speed of the cyclone was low (high) and took more (less) time to recover to its pre-cyclone state in southern (northern) BoB. Mostly, higher SST drop was observed along the right side of the cyclone track. Interestingly, the opposite phenomenon occurred before landfall, where SST drop was higher on the left due to upwelling in the head bay as observed both from wave rider buoy (WRB) at Digha and satellite SST. The WRB near Vizag showed the maximum increase in significant wave heights by ~ 2.4 m during the passage of cyclone. Argos also captured cyclone-induced drop in temperature due to upwelling and entrainment reasonably well. In the southwestern bay, significant upwelling was observed from the Argos with drop in temperature and increase in salinity in the upper layers. However, a strong stratification was observed from Argos in the northwestern BoB due to lesser salinity and higher precipitation. The currents from in situ as well as HF radar datasets measured the increase in current magnitude during the passage of ROANU. Rotary spectral analysis showed strong inertial currents with frequency ~ 2.1 days at BD11 location, with higher amplitudes of the clockwise component during the cyclone period.

Typhoon-induced ocean subsurface variations from glider data in the Kuroshio region adjacent to Taiwan

Underwater gliders are used to investigate the variations on the ocean surface and subsurface during the 14 typhoons that passed over the Kuroshio region near Taiwan in 2010–2013. Typhoon-induced subsurface layer warming, which was formed on the basis of the heat pump effect of the vertical mixing process, is observed in this study. In addition, the gliders observe the variations in salinity during the passage of the typhoons. Typhoons, accompanied by heavy rainfall, introduce a considerable amount of fresh water into the upper ocean, diluting the surface salinity. The diluted salinity accompanied deepening of the mixed layer which moved downward to the subsurface by vertical mixing, supplying fresh water to both the surface and subsurface layers. Additionally, because of vertical mixing, maximum temperature variations occur at the bottom of the mixed layer or at a level deeper than the mixed layer. Changes of the heat content show that a series of vertical mixing events occurs in the upper ocean. Pairs of salinity profiles indicate comprehensive vertical mixing in the upper ocean and yield schematics to compare typhoons with or without heavy rainfall. Higher sustained wind speeds may contribute to a considerable drop in sea surface temperature, but possibly not to the magnitude of the subsurface warming. The upper ocean thermocline gradient before a typhoon is an important factor to determine the magnitude of subsurface warming. This study concludes a glider observational result that typhoons cause subsurface layer warming and freshening in the Kuroshio region near Taiwan.

Evaluation of Satellite-Derived SST Products in Identifying the Rapid Temperature Drop on the West Florida Shelf Associated With Hurricane Irma

AbstractSatellite-derived daily sea surface temperature (SST) products are compared with moored SST observations on the West Florida Shelf during the time period of Hurricane Irma. Most of the SST products compare reasonably well with the moored data at the location of 25-m depth, where SST dropped by about 1°C after the hurricane passage. However, most of the SST products did not show the rapid SST drop at the location of 50-m depth where the surface water was cooled by about 4°C within 1 day in response to the hurricane passage. This finding has important implications to air-sea interaction studies and hurricane simulations, in which SST data play an important role. The limitations of the popular satellite products call for additional coastal ocean observations as well as proper inclusion of the real-time observations in satellite-derived products.

Cretaceous calcareous dinoflagellate cysts as recorder of δ44/40Caseawater and paleo-temperature using Sr/Ca thermometry

We evaluate the potential of calcareous dinoflagellates as archives for Sr/Ca-based paleo-temperature reconstructions and δ44/40Caseawater fluctuations on sediments from Ocean Drilling Program Expedition 113 (Hole 690C, Weddell Sea, Southern Ocean). Between 73 and 68 Ma, Sr/Ca ratios of two Cretaceous dinoflagellate species, Pirumella krasheninnikovii and Orthopithonella globosa show a pronounced decrease, consistent with a significant drop in sea-surface temperature as reflected by the δ18O of planktic foraminifers. The apparent temperature sensitivity of the dinoflagellate cysts' Sr/Ca is ~0.06 and ~0.08 mmol/mol °C−1, using δ18O-derived paleo sea-surface temperatures, which is significant and large enough to resolve paleoenvironmental temperature changes at current analytical precision. As the chemical composition of the cyst calcite appears to have a good preservation, the Sr/Ca of calcareous dinoflagellates has a potential to serve as paleo-temperature proxy, although the chemical composition of the Cretaceous seawater and potential impacts on the cyst geochemistry is pending further inspection.The Ca isotope composition of the two dinoflagellate species shows identical trends of increasing δ44/40Ca between 73 and 67 Ma. The planktic foraminifer Archaeoglobigerina australis and the benthic foraminifer Nuttallides truempyi reveal the same increase of about 0.4‰ but are offset relative to the dinoflagellates by about +0.5‰, presumably due to species-specific Ca isotope fractionation. Bulk carbonate sediment shows significant scatter, likely caused by changes in faunal composition and does not reproduce the trend revealed by the dinoflagellate and foraminifer records. These observations demonstrate the importance of taxon-specific records and careful determination of fractionation factors of selected archives and highlight complications arising from utilizing less suitable archives, such as bulk sediments, for δ44/40Caseawater reconstructions. Our records indicate strong changes in the marine Ca cycle associated with the global temperature decrease towards the end of the Cretaceous.

A Madden‐Julian Oscillation event remotely accelerates ocean upwelling to abruptly terminate the 1997/1998 super El Niño

AbstractThe termination of the superintense 1997/1998 El Niño was extraordinarily abrupt. The May 1998 Madden‐Julian Oscillation (MJO), a massive complex of stormy tropical clouds, is among possible contributors to the abrupt termination. Despite having been sensationally proposed 18 years ago, the role of the MJO remained controversial and speculative because of the difficulty of sufficiently simulating the El Niño and MJO simultaneously. An ensemble simulation series using a newly developed, fully ocean‐coupled version of a global cloud system resolving numerical model replicated the specific atmosphere and ocean conditions of May 1998 in unprecedented detail, extending the prediction skill of the MJO to 46 days. Simulation ensemble members with stronger MJO activities over the Maritime Continent experienced quicker sea surface temperature drop in the eastern Pacific, confirming that the easterly winds associated with the remote MJO accelerated ocean upwelling to abruptly terminate the El Niño.

Effects of typhoon events on chlorophyll and carbon fixation in different regions of the East China Sea

Typhoons play an important role in the regulation of phytoplankton biomass and carbon fixation in the ocean. Data from the moderate-resolution imaging spectroradiometer (MODIS) on 35 typhoon events during 2002–2011 are analyzed to examine the effects of typhoon events on variations in sea surface temperature (SST), chlorophyll-a (Chl-a), and depth-integrated primary productivity (IPP) in the East China Sea (ECS). For all 35 typhoon cases, the average SST drops by 0.1 °C in the typhoon influenced regions, and the maximal decrease is 2.2 °C. During the same period, average Chl-a increases by 0.1 mg m−3, with the maximal increase reaching up to 1 mg m−3, and average IPP increases by 32.9 mg C m−2·d−1, with the largest increase being 221 mg C m−2·d−1. The IPP are significantly correlated with SST and Chl-a data, and the correlations become stronger after typhoon passage. On average, nearly one-third of the ECS is affected by typhoons during the 10 year period, and the resident time of the typhoons in the area reach to 38.2 h. Effects of the typhoon events on SST, Chl-a, and IPP manifest differently in the three key sea areas, namely, the coastal water (depths <50 m), continental shelf (depths 50–200 m), and open sea (depths >200 m) regions in the ECS. Specifically, stronger responses are observed in shallow water than in deeper depths. The comparisons between the pre- and post-typhoon periods show that IPP in the post-typhoon period increases by 19.7% and 12.2% in the coastal and continental shelf regions, respectively, but it decreases by 9.4% in the open sea region. Overall, our results reveal that there is a close coupling between Chl-a, SST, and IPP in shallow areas and that typhoon events can have strong effects on carbon fixation in coastal regions.

Monsoonal upwelling in the western Arabian Sea since the middle Miocene

Research Article| July 01, 2017 Monsoonal upwelling in the western Arabian Sea since the middle Miocene Guangsheng Zhuang; Guangsheng Zhuang 1Department of Geology and Geophysics, Louisiana State University, Baton Rouge, Louisiana 70803, USA Search for other works by this author on: GSW Google Scholar Mark Pagani; Mark Pagani 2Department of Geology and Geophysics, Yale University, New Haven, Connecticut 06520, USA Search for other works by this author on: GSW Google Scholar Yi Ge Zhang Yi Ge Zhang 3Department of Oceanography, Texas A&M University, College Station, Texas 77843, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Guangsheng Zhuang 1Department of Geology and Geophysics, Louisiana State University, Baton Rouge, Louisiana 70803, USA Mark Pagani 2Department of Geology and Geophysics, Yale University, New Haven, Connecticut 06520, USA Yi Ge Zhang 3Department of Oceanography, Texas A&M University, College Station, Texas 77843, USA Publisher: Geological Society of America Received: 01 Feb 2017 Revision Received: 21 Mar 2017 Accepted: 21 Mar 2017 First Online: 28 Jun 2017 Online Issn: 1943-2682 Print Issn: 0091-7613 © 2017 Geological Society of America Geology (2017) 45 (7): 655–658. https://doi.org/10.1130/G39013.1 Article history Received: 01 Feb 2017 Revision Received: 21 Mar 2017 Accepted: 21 Mar 2017 First Online: 28 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Guangsheng Zhuang, Mark Pagani, Yi Ge Zhang; Monsoonal upwelling in the western Arabian Sea since the middle Miocene. Geology 2017;; 45 (7): 655–658. doi: https://doi.org/10.1130/G39013.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The Asian monsoon has long been argued to be a product of the Himalaya–Tibetan Plateau, and simulation experiments have confirmed the key role of the Himalaya–Tibetan Plateau in transforming regional atmospheric and oceanic circulations. However, temporal constraints on the strengthening of the Asian monsoon inferred from foraminifer isotopic and faunal data and terrestrial climatic and ecological records are inconsistent with each other, which has obscured the tectonic-climatic linkage. In particular, discriminating the post-middle Miocene global cooling from the monsoon upwelling cooling is critical, but poorly understood due to the lack of adequate constraints for monsoonal upwelling. Here we present new middle to late Miocene biomarker-based reconstructions of sea-surface temperature (SST) for the western Arabian Sea. Our new SSTs capture a long-term ocean cooling since ca. 14.8 Ma and a major drop in SST in the period 11–10 Ma after which the SSTs reached similar values as the Holocene. The new SST record is consistent with planktonic foraminifer, siliceous biota, and geochemical tracer studies, suggestive of ocean cooling and high productivity associated with monsoonal upwelling. The 11–10 Ma ocean cooling is not clearly expressed in other tropical oceans, indicating that the ocean cooling in the western Arabian Sea is not a simple reflection of global cooling. We interpret the 11–10 Ma ocean cooling as representing the establishment of monsoonal upwelling in the western Arabian Sea, triggered by strong cyclonic activities as a result of the Neogene outward expansion of the Himalaya–Tibetan Plateau. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The impacts of 2008 snowstorm in China on the ecological environments in the Northern South China Sea

ABSTRACTAt the beginning of 2008, disastrous weather with snowstorms truck South China. Analysis of satellite and in situ data revealed obvious changes in ecological environments in the northern South China Sea after snowstorms. The sea surface temperature (SST) data from NOAA and Moderate Resolution Imaging Spectroradiometer (MODIS) from 2000 to 2013, and the chlorophyll-a (Chla) concentration from MODIS are analysed. In the study area, the multiple-day-averaged SST dropped by 20.01% and Chla concentration increased by 22.42% during and after snowstorm. SST decreased more significantly and Chla increased in the coastal waters, while suspended sediment concentration (SSC) increased more remarkably offshore. The biggest drop of SST reached 6°C and striking elevation in Chla with 52.55% in the Taiwan Strait, and SSC changed significantly near to the Taiwan bank after the snowstorm. Further analysis indicated that the remarkable reductions in SST were caused by large cold water input from Min-Zhe coastal water and the Pearl River Estuary, as a result of strong sea-land-air interaction in the coastal waters during the snowstorm. The increase in Chla may be related to the abundant nutrients from the plenty of cold water, a strong front and vertical mixing in the coastal waters.

Ocean atmosphere thermal decoupling in the eastern equatorial Indian ocean

Eastern equatorial Indian ocean (EEIO) is one of the most climatically sensitive regions in the global ocean, which plays a vital role in modulating Indian ocean dipole (IOD) and El Nino southern oscillation (ENSO). Here we present evidences for a paradoxical and perpetual lower co-variability between sea-surface temperature (SST) and air-temperature (Tair) indicating instantaneous thermal decoupling in the same region, where signals of the strongly coupled variability of SST anomalies and zonal winds associated with IOD originate at inter-annual time scale. The correlation minimum between anomalies of Tair and SST occurs in the eastern equatorial Indian ocean warm pool region (≈70°E–100°E, 5°S–5°N), associated with lower wind speeds and lower sensible heat fluxes. At sub-monthly and Madden–Julian oscillation time scales, correlation of both variables becomes very low. In above frequencies, precipitation positively contributes to the low correlation by dropping Tair considerably while leaving SST without any substantial instant impact. Precipitation is led by positive build up of SST and post-facto drop in it. The strong semi-annual response of SST to mixed layer variability and equatorial waves, with the absence of the same in the Tair, contributes further to the weak correlation at the sub-annual scale. The limited correlation found in the EEIO is mainly related to the annual warming of the region and ENSO which is hard to segregate from the impacts of IOD.

Elucidating the potential squid habitat responses in the central North Pacific to the recent ENSO flavors

The effects of the El Nino Southern Oscillation (ENSO)-mediated environmental changes to marine resources were long recognized; however, species-specific responses were also reported to vary, possibly more so, under the emerging event-to-event diversity of the ENSO conditions. Hence, the objective of this study is to characterize the potential impacts of the ENSO-regulated environmental variability to squid habitat in the central North Pacific under the different ENSO flavors, using habitat models developed from at least a decade of fishery-dependent dataset and environmental parameters. Our findings revealed that the potential squid habitats were largely influenced by ENSO-forced environmental changes during the squid’s spawning and nursery periods, resulting in substantial reduction/enhancement of available habitats in the succeeding summers of Central Pacific El Nino/La Nina, where the latter led to an expansion of favorable spawning and nursery grounds. However, the autumn–winter periods of weaker and short-lived Eastern Pacific El Nino showed elevated potential habitats due to minimal sea surface temperature drop and close proximity of spawning and nursery grounds to optimal feeding environments. The quick, albeit variable, squids’ responses to ENSO flavors accentuate their promising potential as ecological beacons under climate changes, aiding the development of adaptive management strategies for commercially exploited fisheries.