Deterioration of symbiont-bearing morozovellid (planktic foraminifera) habitat recorded within the Early Eocene Climatic Optimum: evidence from the Tethys and sub-tropical Atlantic Ocean

2014 ◽  
Vol 31 ◽  
pp. 145-146
Author(s):  
Valeria Luciani
Keyword(s):  
Atlantic Ocean ◽  
Early Eocene ◽  
Tropical Atlantic ◽  
Planktic Foraminifera ◽  
Tropical Atlantic Ocean ◽  
Early Eocene Climatic Optimum ◽  
Climatic Optimum

Dominant dextral to sinistral coiling change in planktic foraminifera Morozovella during the Early Eocene Climatic Optimum in the Atlantic Ocean

2020 ◽  
Author(s):  
Valeria Luciani ◽  
Roberta D'Onofrio ◽  
Wade Bridget S. ◽  
Dickens Jerry R.
Keyword(s):  
Atlantic Ocean ◽  
Stable Carbon Isotopes ◽  
Environmental Parameters ◽  
Single Species ◽  
Early Eocene ◽  
Planktic Foraminifera ◽  
Early Eocene Climatic Optimum ◽  
Climatic Optimum ◽  
Coiling Direction ◽  
Early Paleogene

<p>Coiling direction is a basic characteristic of trochospiral planktic foraminifera. However, although modifications in the coiling direction within ancient planktic foraminiferal populations may reflect important changes in evolution or environment, they remain scarcely discussed. Here we present data on fluctuations in the coiling direction within morphologically defined Morozovella species from successions that span the interval of peak Cenozoic warmth, the Early Eocene Climatic Optimum (EECO; ~53-49 Ma). We selected three widely separated Ocean Drilling Program (ODP) sites in the Atlantic Ocean: the subtropical Site 1051, the equatorial Site 1258 and the temperate south Atlantic Site 1263. The surface-dwelling genus Morozovella is of particular interest because it dominated tropical-subtropical early Paleogene assemblages and  suffered an abrupt and permanent decline in abundance and taxonomic diversity at the start of the EECO. At all ODP sites investigated, morozovellids display a dominant dextral coiling preference during the interval preceding the EECO. However, all species became at all sites prevailing sinistral within the EECO. Specifically, the switch from dominant dextral to sinistral coiling occurred at all sites ~ 300 Kyr after the K/X event (~52.8 Ma). The coiling switch occurred ~550 kyr to ~650 kyr after a distinct drop in abundance. We provide therefore evidence of a coiling variation during the warmest interval of the early Paleogene. Our records highlight that the recorded coiling variations might provide a biostratigraphic tool for correlation of early Eocene marine strata. In order to establish whether this coiling switch was related to changes in morozovellid ecological niche we estimated stable carbon isotopes on dextral and sinistral species from samples located below and above the recorded coiling change. Results suggest that sinistral species moved higher in the mixed-layer after the coiling switch. It is thus possible that only species sinistrally coiled were able to keep the optimal environmental conditions for their survivorship. We need however more effort to understand the meaning of these modifications, such to verify whether variations in sea surface temperature or other parameters directly corresponded to the coiling change. Coiling switches can relate to ecophenotypic adaption (when a single species changes morphology in response to variation in environmental parameters, such as temperature) or genetic variance (when two almost identical morphotypes have different genetic signatures so they represent ‘cryptic’ species from a morphological point of view). Previous interpretations of coiling flips in planktic foraminifera in the early Eocene, especially including morozovellids, have favoured a genetic explanation rather than an ecological response. Our present data cannot validate or disprove this idea, but should stimulate renewed thought on the matter.</p>

scholarly journals Demise of the Planktic Foraminifer Genus Morozovella during the Early Eocene Climatic Optimum: New Records from ODP Site 1258 (Demerara Rise, Western Equatorial Atlantic) and Site 1263 (Walvis Ridge, South Atlantic)

Geosciences ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 88 ◽  
Author(s):  
Roberta D’Onofrio ◽  
Valeria Luciani ◽  
Gerald R. Dickens ◽  
Bridget S. Wade ◽  
Sandra Kirtland Turner
Keyword(s):  
Planktonic Foraminifera ◽  
Early Eocene ◽  
Equatorial Atlantic ◽  
Ocean Drilling Program ◽  
Planktic Foraminifera ◽  
Ocean Drilling ◽  
Early Eocene Climatic Optimum ◽  
Dominant Component ◽  
Climatic Optimum ◽  
Early Paleogene

Here we present relative abundances of planktic foraminifera that span the Early Eocene Climatic Optimum (EECO) at Ocean Drilling Program (ODP) Site 1258 in the western equatorial Atlantic. The EECO (~53.3−49.1 Ma) represents peak Cenozoic warmth, probably related to high atmospheric CO2, and when planktic foraminifera, a dominant component of marine sediment, exhibit a major biotic response. Consistent with previous work, the relative abundance of the genus Morozovella, which dominated early Paleogene tropical-subtropical assemblages, markedly and permanently declined from a mean percentage of ~32% to less than ~7% at the beginning of the EECO. The distinct decrease in Morozovella abundance occurred at Site 1258 within ~20 kyr before a negative excursion in δ13C records known as the J event and which defines the beginning of EECO. Moreover, all morozovellid species except M. aragonensis dropped in abundance permanently at Site 1258, and this is related to a reduction in test-size. Comparing our data with that from other locations, the remarkable switch in planktonic foraminifera assemblages appears to have begun first with unfavourable environmental conditions near the Equator and then extended to higher latitudes. Several potential stressors may explain observations, including some combination of algal photosymbiont inhibition (bleaching), a sustained increase in temperature, or an extended decrease in pH.

scholarly journals Massive and permanent decline of symbiont bearing morozovellids and δ<sup>13</sup>C perturbations across the Early Eocene Climatic Optimum at the Possagno section (Southern Alps of northeastern Italy)

2015 ◽  
Vol 11 (2) ◽  
pp. 671-712
Author(s):  
V. Luciani ◽  
J. Backman ◽  
E. Fornaciari ◽  
L. Giusberti ◽  
C. Agnini ◽  
...  
Keyword(s):  
Climate Change ◽  
Relative Abundance ◽  
Early Eocene ◽  
Planktic Foraminifera ◽  
Early Eocene Climatic Optimum ◽  
Water Column Stratification ◽  
Stable Isotopic ◽  
Northeastern Italy ◽  
Climatic Optimum ◽  
Early Paleogene

Abstract. The Early Eocene Climatic Optimum (EECO) records the highest prolonged global temperatures over the past 70 Ma. Understanding the causes and timing of Eocene climate change remains a major challenge in Cenozoic paleoceanography, which includes the biotic response to climate variability and the changes among planktic foraminiferal assemblages across the EECO. The symbiont bearing and shallow dwelling genera Morozovella and Acarinina were important calcifiers in the tropical-subtropical early Paleogene oceans but almost completely disappeared at about 38 Ma, near the Bartonian/Priabonian boundary. We show here that morozovellids record a first critical step across the EECO through a major permanent decline in relative abundance from the Tethyan Possagno section and ODP Site 1051 in the western subtropical North Atlantic. Possible causes may include increased eutrophication, weak water column stratification, changes in ocean chemistry, loss of symbiosis and possible complex interaction with other microfossil groups. Relative abundances of planktic foraminiferal taxa at Possagno parallel negative shifts in both δ13C and δ18O of bulk sediment from Chron C24r to basal Chron C20r. The post-EECO stable isotopic excursions towards lighter values are of modest intensity. Significant though ephemeral modifications in the planktic foraminiferal communities occur during these minor isotopic excursions. These modifications are marked by pronounced increases in relative abundance of acarininids, in a manner similar to their behaviour during pre-EECO hyperthermals in the Tethyan settings, which suggest a pronounced biotic sensitivity to climate change of planktic foraminifera even during the post-EECO interval.

scholarly journals Correction to: Weakened SST variability in the tropical Atlantic Ocean since 2000

2021 ◽  
Author(s):  
Arthur Prigent ◽  
Joke F. Lübbecke ◽  
Tobias Bayr ◽  
Mojib Latif ◽  
Christian Wengel
Keyword(s):  
Atlantic Ocean ◽  
Tropical Atlantic ◽  
Tropical Atlantic Ocean ◽  
Sst Variability

scholarly journals Simulated Dust Aerosol Impacts on Western Sahelian Rainfall: Importance of Ocean Coupling

2018 ◽  
Vol 31 (22) ◽  
pp. 9107-9124 ◽  
Author(s):  
Asha K. Jordan ◽  
Anand Gnanadesikan ◽  
Benjamin Zaitchik
Keyword(s):  
Atlantic Ocean ◽  
North Africa ◽  
Negative Impact ◽  
Positive Impact ◽  
Geophysical Fluid Dynamics Laboratory ◽  
Tropical Atlantic ◽  
Tropical Atlantic Ocean ◽  
Ocean Atmosphere ◽  
Sahel Region ◽  
Dust Precipitation

North Africa is the world’s largest source of mineral dust, and this dust has potentially significant impacts on precipitation. Yet there is no consensus in published studies regarding the sign or magnitude of dust impacts on rainfall in either the highly climate-sensitive Sahel region of North Africa or the neighboring tropical Atlantic Ocean. Here the Geophysical Fluid Dynamics Laboratory (GFDL) Climate Model 2 (GFDL CM2.0) with Modular Ocean Model, version 4.1 (MOM4.1), run at coarse resolution (CM2Mc) is applied to investigate one poorly characterized aspect of dust–precipitation dynamics: the importance of sea surface temperature (SST) changes in mediating the atmospheric response to dust. Two model experiments were performed: one comparing Dust-On to Dust-Off simulations in the absence of ocean–atmosphere coupling, and the second comparing Dust-On to Dust-Off with the ocean fully coupled. Results indicate that SST changes in the coupled experiment reduce the magnitude of dust impacts on Sahel rainfall and flip the sign of the precipitation response over the nearby ocean. Over the Sahel, CM2Mc simulates a net positive impact of dust on monsoon season rainfall, but ocean–atmosphere coupling in the presence of dust decreases the inflow of water vapor, reducing the amount by which dust enhances rainfall. Over the tropical Atlantic Ocean, dust leads to SST cooling in the coupled experiment, resulting in increased static stability that overrides the warming-induced increase in convection observed in the uncoupled experiment and yields a net negative impact of dust on precipitation. These model results highlight the potential importance of SST changes in dust–precipitation dynamics in North Africa and neighboring regions.

scholarly journals Impact of intraseasonal wind bursts on sea surface temperature variability in the far eastern tropical Atlantic Ocean during boreal spring 2005 and 2006: focus on the mid-May 2005 event

Ocean Science ◽  
2018 ◽  
Vol 14 (4) ◽  
pp. 849-869 ◽  
Author(s):  
Gaëlle Herbert ◽  
Bernard Bourlès
Keyword(s):  
Atlantic Ocean ◽  
Surface Temperature ◽  
Kelvin Waves ◽  
Sea Surface ◽  
Tropical Atlantic ◽  
Gulf Of Guinea ◽  
Atmospheric Conditions ◽  
Tropical Atlantic Ocean ◽  
Boreal Spring ◽  
Wind Bursts

Abstract. The impact of boreal spring intraseasonal wind bursts on sea surface temperature variability in the eastern tropical Atlantic Ocean in 2005 and 2006 is investigated using numerical simulation and observations. We especially focus on the coastal region east of 5° E and between the Equator and 7° S that has not been studied in detail so far. For both years, the southerly wind anomalies induced cooling episodes through (i) upwelling processes, (ii) vertical mixing due to the vertical shear of the current, and for some particular events (iii) a decrease in incoming surface shortwave radiation. The strength of the cooling episodes was modulated by subsurface conditions affected by the arrival of Kelvin waves from the west influencing the depth of the thermocline. Once impinging the eastern boundary, the Kelvin waves excited westward-propagating Rossby waves, which combined with the effect of enhanced westward surface currents contributed to the westward extension of the cold water. A particularly strong wind event occurred in mid-May 2005 and caused an anomalous strong cooling off Cape Lopez and in the whole eastern tropical Atlantic Ocean. From the analysis of oceanic and atmospheric conditions during this particular event, it appears that anomalously strong boreal spring wind strengthening associated with anomalously strong Hadley cell activity prematurely triggered the onset of coastal rainfall in the northern Gulf of Guinea, making it the earliest over the 1998–2008 period. No similar atmospheric conditions were observed in May over the 1998–2008 period. It is also found that the anomalous oceanic and atmospheric conditions associated with the event exerted a strong influence on rainfall off northeast Brazil. This study highlights the different processes through which the wind power from the South Atlantic is brought to the ocean in the Gulf of Guinea and emphasizes the need to further document and monitor the South Atlantic region.

The barrier layer in the western tropical Atlantic Ocean

1999 ◽  
Vol 26 (14) ◽  
pp. 2069-2072 ◽  
Author(s):  
K. Pailler ◽  
B. Bourlès ◽  
Y. Gouriou
Keyword(s):  
Atlantic Ocean ◽  
Barrier Layer ◽  
Tropical Atlantic ◽  
Tropical Atlantic Ocean
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