scholarly journals Radiocarbon Reservoir Age Variations in the South Peruvian Upwelling During the Holocene

Radiocarbon ◽  
2004 ◽  
Vol 46 (2) ◽  
pp. 531-537 ◽  
Author(s):  
Michel Fontugne ◽  
Matthieu Carré ◽  
Ilhem Bentaleb ◽  
Michèle Julien ◽  
Danièle Lavallée
Keyword(s):  
Ocean Circulation ◽  
Coastal Upwelling ◽  
Sea Surface ◽  
Intermediate Depth ◽  
The Holocene ◽  
Middle Holocene ◽  
Age Variations ◽  
The Difference ◽  
Upwelling Intensity ◽  
Reservoir Age

In Quebrada de los Burros in coastal southern Peru (Tacna department), human settlements containing shells and charcoal deposits have been excavated since 1995. The sea surface 14C reservoir ages, estimated by calculating the difference of 14C age between marine shells and terrestrial organic materials, exhibit high values during the lower and middle Holocene and decrease abruptly after 4000 cal BP. The increase of reservoir age at around 7000–8000 cal BP suggests an enhancement of Peruvian coastal upwelling intensity and changes in ocean circulation at intermediate depth.

scholarly journals Middle Holocene expansion of Pacific Deep Water into the Southern Ocean

2019 ◽  
Vol 117 (2) ◽  
pp. 889-894
Author(s):  
Torben Struve ◽  
David J. Wilson ◽  
Tina van de Flierdt ◽  
Naomi Pratt ◽  
Kirsty C. Crocket
Keyword(s):  
Southern Ocean ◽  
Ocean Circulation ◽  
Deep Water ◽  
Water Masses ◽  
Ocean Dynamics ◽  
Global Ocean ◽  
Circulation System ◽  
The Holocene ◽  
Middle Holocene ◽  
Deep Mixing

The Southern Ocean is a key region for the overturning and mixing of water masses within the global ocean circulation system. Because Southern Ocean dynamics are influenced by the Southern Hemisphere westerly winds (SWW), changes in the westerly wind forcing could significantly affect the circulation and mixing of water masses in this important location. While changes in SWW forcing during the Holocene (i.e., the last ∼11,700 y) have been documented, evidence of the oceanic response to these changes is equivocal. Here we use the neodymium (Nd) isotopic composition of absolute-dated cold-water coral skeletons to show that there have been distinct changes in the chemistry of the Southern Ocean water column during the Holocene. Our results reveal a pronounced Middle Holocene excursion (peaking ∼7,000–6,000 y before present), at the depth level presently occupied by Upper Circumpolar Deep Water (UCDW), toward Nd isotope values more typical of Pacific waters. We suggest that poleward-reduced SWW forcing during the Middle Holocene led to both reduced Southern Ocean deep mixing and enhanced influx of Pacific Deep Water into UCDW, inducing a water mass structure that was significantly different from today. Poleward SWW intensification during the Late Holocene could then have reinforced deep mixing along and across density surfaces, thus enhancing the release of accumulated CO2 to the atmosphere.

scholarly journals Spatial and temporal variability of the dimethylsulfide to chlorophyll ratio in the surface ocean: an assessment based on phytoplankton group dominance determined from space

2010 ◽  
Vol 7 (10) ◽  
pp. 3215-3237 ◽  
Author(s):  
I. Masotti ◽  
S. Belviso ◽  
S. Alvain ◽  
J. E. Johnson ◽  
T. S. Bates ◽  
...  
Keyword(s):  
Coastal Upwelling ◽  
Spatial Scales ◽  
Horizontal Resolution ◽  
Sea Surface ◽  
Spatial And Temporal Variability ◽  
Phytoplankton Assemblages ◽  
The Pacific ◽  
Significant Difference ◽  
The Difference ◽  
Phytoplankton Group

Abstract. Dimethylsulfoniopropionate (DMSP) is produced in surface seawater by phytoplankton. Phytoplankton culture experiments have shown that nanoeucaryotes (NANO) display much higher mean DMSP-to-Carbon or DMSP-to-Chlorophyll (Chl) ratios than Prochlorococcus (PRO), Synechococcus (SYN) or diatoms (DIAT). Moreover, the DMSP-lyase activity of algae which cleaves DMSP into dimethylsulfide (DMS) is even more group specific than DMSP itself. Ship-based observations have shown at limited spatial scales, that sea surface DMS-to-Chl ratios (DMS:Chl) are dependent on the composition of phytoplankton groups. Here we use satellite remote sensing of Chl (from SeaWiFS) and of Phytoplankton Group Dominance (PGD from PHYSAT) with ship-based sea surface DMS concentrations (8 cruises in total) to assess this dependence on an unprecedented spatial scale. PHYSAT provides PGD (either NANO, PRO, SYN, DIAT, Phaeocystis (PHAEO) or coccolithophores (COC)) in each satellite pixel (1/4° horizontal resolution). While there are identification errors in the PHYSAT method, it is important to note that these errors are lowest for NANO PGD which we typify by high DMSP:Chl. In summer, in the Indian sector of the Southern Ocean, we find that mean DMS:Chl associated with NANO + PHAEO and PRO + SYN + DIAT are 13.6±8.4 mmol g−1 (n=34) and 7.3±4.8 mmol g−1 (n=24), respectively. That is a statistically significant difference (P<0.001) that is consistent with NANO and PHAEO being relatively high DMSP producers. However, in the western North Atlantic between 40° N and 60° N, we find no significant difference between the same PGD. This is most likely because coccolithophores account for the non-dominant part of the summer phytoplankton assemblages. Meridional distributions at 22° W in the Atlantic, and 95° W and 110° W in the Pacific, both show a marked drop in DMS:Chl near the equator, down to few mmol g−1, yet the basins exhibit different PGD (NANO in the Atlantic, PRO and SYN in the Pacific). In tropical and subtropical Atlantic and Pacific waters away from the equatorial and coastal upwelling, mean DMS:Chl associated with high and low DMSP producers are statistically significantly different, but the difference is opposite of that expected from culture experiments. Hence, in a majority of cases PGD is not of primary importance in controlling DMS:Chl variations. We therefore conclude that water-leaving radiance spectra obtained simultaneously from ocean color sensor measurements of Chl concentrations and dominant phytoplankton groups can not be used to predict global fields of DMS.

scholarly journals Paired 14C and 230Th/U Dating of Surface Corals from the Marquesas and Vanuatu (Sub-Equatorial Pacific) in the 3000 to 15,000 Cal Yr Interval

Radiocarbon ◽  
2004 ◽  
Vol 46 (2) ◽  
pp. 551-566 ◽  
Author(s):  
Martine Paterne ◽  
Linda K Ayliffe ◽  
Maurice Arnold ◽  
Guy Cabioch ◽  
Nadine Tisnérat-Laborde ◽  
...  
Keyword(s):  
Surface Waters ◽  
Sea Surface ◽  
Marquesas Islands ◽  
Rapid Changes ◽  
Mean Sea Surface ◽  
The Absolute ◽  
The Difference ◽  
Surface Reservoir ◽  
Reservoir Age ◽  
Submerged Reefs

Paired radiocarbon and 230Th/U dating was performed on 13 surface corals from submerged reefs in the Marquesas and from raised terraces in Vanuatu. The absolute ages of the corals analyzed ranged from 3000 to 15,000 cal yr. Estimates of the difference between the absolute and 14C ages of these corals are in agreement with previous determinations up until 11,500 cal yr. The resulting mean sea surface reservoir age R is determined at 390 ± 60 yr for the Marquesas region (9°S), which is slightly higher than the R value at 280 ± 50 yr for the Tahiti Islands (18°S). Multiple 14C analyses of 2 corals from the Marquesas present scattered 14C ages at ~12,000 and ~15,100 cal yr. This could be attributed to rapid changes of the 14C content of surface waters around the Marquesas Islands or to a subtle submarine diagenesis.

scholarly journals Modeling variations of marine reservoir ages during the last 45 000 years

2008 ◽  
Vol 4 (2) ◽  
pp. 125-136 ◽  
Author(s):  
J. Franke ◽  
A. Paul ◽  
M. Schulz
Keyword(s):  
Ocean Circulation ◽  
Circulation Model ◽  
Temporal Variations ◽  
Global Ocean ◽  
Large Reservoir ◽  
Tropical Regions ◽  
Age Variations ◽  
Temporal And Spatial ◽  
Global Ocean Circulation ◽  
Reservoir Age

Abstract. When dating marine samples with 14C, the reservoir-age effect is usually assumed to be constant, although atmospheric 14C production rate and ocean circulation changes cause temporal and spatial reservoir-age variations. These lead to dating errors, which can limit the interpretation of cause and effect in paleoclimate data. We used a global ocean circulation model forced by transient atmospheric Δ14C variations to calculate reservoir ages for the last 45 000 years for a present day-like and a last glacial maximum-like ocean circulation. A ~30% reduced Atlantic meridonal overturning circulation leads to increased reservoir ages by up to ~500 years in high latitudes. Temporal variations are proportional to the absolute value of the reservoir age; regions with large reservoir age also show large variation. Temporal variations range between ~300 years in parts of the subtropics and ~1000 years in the Southern Ocean. For tropical regions, which are generally assumed to have nearly stable reservoir ages, the model suggests variations of several hundred years.

scholarly journals Surface expression of Mediterranean Water dipoles and their contribution to the shelf/slope – open ocean exchange

Ocean Science ◽  
2010 ◽  
Vol 6 (1) ◽  
pp. 191-209 ◽  
Author(s):  
N. Serra ◽  
I. Ambar ◽  
D. Boutov
Keyword(s):  
Ocean Circulation ◽  
Coastal Upwelling ◽  
Model Simulation ◽  
Chlorophyll Concentration ◽  
Surface Expression ◽  
Open Ocean ◽  
Sea Surface ◽  
Shelf Slope ◽  
The Impact ◽  
Mediterranean Water

Abstract. The generation of dipolar eddies within the Mediterranean Water (MW) layers, at the Portuguese continental slope, was observed using subsurface RAFOS floats. The surface expression of these mid-depth dipoles is here characterized with remote sensing data, namely with sea surface temperature, chlorophyll concentration and sea surface height measurements. Two cases are presented demonstrating the remote detection of these underwater structures in the Gulf of Cadiz during 1998 and 2001. The presence of subsurface MW dipoles in the Iberian coastal zone is shown to influence the development of coastal upwelling filaments. The surface circulation induced by the dipoles causes the upwelling filaments to extend offshorewards and thus to enhance the transport of physical, chemical and biological properties into the open ocean. A numerical model simulation of the ocean circulation around the Iberian Peninsula forced by heat and freshwater fluxes (computed using the NCEP reanalysis atmospheric state) and by the overflow of MW at the Strait of Gibraltar, corroborates the connection between the surface and the mid-depth flows. The high-resolution numerical experiment is used to help clarifying the occurrence of the MW dipoles surface expression and the impact of these dipoles on the eddy kinetic energy of the upper ocean and on the exchange of volume and salt between the shelf/slope and the open ocean.

scholarly journals Surface expression of Mediterranean Water dipoles and their contribution to the shelf/slope – open ocean exchange

2009 ◽  
Vol 6 (3) ◽  
pp. 2579-2623 ◽  
Author(s):  
N. Serra ◽  
I. Ambar ◽  
D. Boutov
Keyword(s):  
Ocean Circulation ◽  
Coastal Upwelling ◽  
Model Simulation ◽  
Chlorophyll Concentration ◽  
Surface Expression ◽  
Open Ocean ◽  
Sea Surface ◽  
Shelf Slope ◽  
The Impact ◽  
Mediterranean Water

Abstract. The generation of dipolar eddies within the Mediterranean Water (MW) layers, at the Portuguese continental slope, was observed using subsurface RAFOS floats. The surface expression of these mid-depth dipoles is here characterized with remote sensing data, namely with sea surface temperature, chlorophyll concentration and sea surface height measurements. Two cases are presented demonstrating the remote detection of these underwater structures in the Gulf of Cadiz during 1998 and 2001. The presence of subsurface MW dipoles in the Iberian coastal zone is shown to influence the development of coastal upwelling filaments. The surface circulation induced by the dipoles causes the upwelling filaments to extend offshorewards and thus to enhance the transport of physical, chemical and biological properties into the open ocean. A numerical model simulation of the ocean circulation around the Iberian Peninsula forced by heat and freshwater fluxes (computed using the NCEP reanalysis atmospheric state) and by the overflow of MW at the Strait of Gibraltar, corroborates the connection between the surface and the mid-depth flows. The high-resolution numerical experiment is used to help clarifying the occurrence of the MW dipoles surface expression and the impact of these dipoles on the eddy kinetic energy of the upper ocean and on the exchange of volume and salt between the shelf/slope and the open ocean.

scholarly journals Responses of Summer Upwelling to Recent Climate Changes in the Taiwan Strait

2021 ◽  
Vol 13 (7) ◽  
pp. 1386
Author(s):  
Caiyun Zhang
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Coastal Upwelling ◽  
Taiwan Strait ◽  
Sea Surface ◽  
Enso Events ◽  
Upwelling System ◽  
Recent Climate ◽  
Upwelling Intensity ◽  
The Taiwan Strait

The response of a summer upwelling system to recent climate change in the Taiwan Strait has been investigated using a time series of sea surface temperature and wind data over the period 1982–2019. Our results revealed that summer upwelling intensities of the Taiwan Strait decreased with a nonlinear fluctuation over the past four decades. The average upwelling intensity after 2000 was 35% lower than that before 2000. The long-term changes in upwelling intensities show strong correlations with offshore Ekman transport, which experienced a decreasing trend after 2000. Unlike the delay effect of canonical ENSO events on changes in summer upwelling, ENSO Modoki events had a significant negative influence on upwelling intensity. Strong El Niño Modoki events were not favorable for the development of upwelling. This study also suggested that decreased upwelling could not slow down the warming rate of the sea surface temperature and would probably cause the decline of chlorophyll a in the coastal upwelling system of the Taiwan Strait. These results will contribute to a better understanding of the dynamic process of summer upwelling in the Taiwan Strait, and provide a sound scientific basis for evaluating future trends in coastal upwelling and their potential ecological effects.

scholarly journals Modeling variations of marine reservoir ages during the last 45 000 years

2008 ◽  
Vol 4 (1) ◽  
pp. 81-110 ◽  
Author(s):  
J. Franke ◽  
A. Paul ◽  
M. Schulz
Keyword(s):  
Ocean Circulation ◽  
Circulation Model ◽  
Temporal Variations ◽  
Global Ocean ◽  
Large Reservoir ◽  
Tropical Regions ◽  
Age Variations ◽  
Temporal And Spatial ◽  
Global Ocean Circulation ◽  
Reservoir Age

Abstract. When dating marine samples with 14C, the reservoir-age effect is usually assumed to be constant, although atmospheric 14C production rate and ocean circulation changes cause temporal and spatial reservoir-age variations. These lead to dating errors, which can limit the interpretation of cause and effect in paleoclimate data. We used a global ocean circulation model forced by transient atmospheric Δ14C variations to calculate reservoir ages for the last 45 000 years for a present day-like and a last glacial maximum-like ocean circulation. A ~30% reduced Atlantic meridonal overturning circulation leads to increased reservoir ages by up to ~500 years in high latitudes. Temporal variations are proportional to the absolute value of the reservoir age; regions with large reservoir age also show large variation. Temporal variations range between ~300 years in parts of the subtropics and ~1000 years in the Southern Ocean. For tropical regions, which are generally assumed to have nearly stable reservoir ages, the model suggests variations of several hundred years.

scholarly journals Environmental Effects on the Spatiotemporal Variability of Fish Larvae in the Western Guangdong Waters, China

2021 ◽  
Vol 9 (3) ◽  
pp. 316
Author(s):  
Yuting Feng ◽  
Lijun Yao ◽  
Hui Zhao ◽  
Jing Yu ◽  
Zhaojin Lin
Keyword(s):  
Environmental Effects ◽  
Coastal Upwelling ◽  
Fish Larvae ◽  
Additive Models ◽  
Sea Surface ◽  
Sea Surface Salinity ◽  
Spatiotemporal Variability ◽  
Aquatic Life ◽  
Positive Effects ◽  
Fishery Resources

Spawning grounds occupy an important position in the survival and reproduction of aquatic life, which plays an important role in the replenishment of fishery resources, especially in the China coasts where fishery resources are depleting. This study investigated environmental effects on the spatiotemporal variability of fish larvae in the western Guangdong waters (WGWs), on the basis of generalized additive models (GAMs) and center of gravity (CoG). Satellite data including sea surface salinity (SSS), sea surface temperature (SST), and in situ observations for fish larvae from April to June in 2014–2015 were used. Results showed that 40.3% of the total variation in fish larvae density was explained. SST, SSS, and depth showed positive effects in 23–24 °C and 27–30 °C, 24–32 PSU, and 0–60 m, and showed negative effects in 24–27 °C, 32–34.2 PSU, 60–80 m. Based on the stepwise GAMs, the most important factor was month, with a contribution of 10.6%, followed by longitude, offshore distance, depth, and latitude, with contributions of 7.0%, 7.0%, 6.3%, 4.2%, 3.9%, and 1.3%, respectively. Fish larvae CoG shifted northward by 0.6° N and eastwards by 0.13° E from April to June. The distribution of fish larvae in the WGWs was affected by complex submarine topography in the Qiongzhou Strait, coastal upwelling in the WGWs, and runoff from the Pearl River.

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