Identification of Density-Stratified Waters in the Late-Pleistocene North Atlantic: A faunal Derivation

1983 ◽  
Vol 20 (3) ◽  
pp. 374-386 ◽  
Author(s):  
Joseph J. Morley
Keyword(s):  
Late Pleistocene ◽  
North Atlantic ◽  
Sea Of Okhotsk ◽  
Species Abundance ◽  
High Abundance ◽  
Northwest Pacific ◽  
The Sea Of Okhotsk ◽  
The North ◽  
The North Atlantic ◽  
Subsurface Temperatures

An expanded study of the radiolarian Cycladophora davisiana in late-Pleistocene North Atlantic marine sediments shows that over the last several hundred thousand years this species exhibits large variations in relative abundance. The C. davisiana curves in the North Atlantic cores are quite similar, with easily recognizable features common to all records. Minor deviations from the general pattern of this species' abundance apparently reflect the response of C. davisiana to specific oceanographic conditions characteristic of a particular area within the North Atlantic. C. davisiana occurs today in high abundance (>20%) only in the Sea of Okhotsk. Extensive winter and early spring sea-ice cover coupled with low surface-water salinities during summer and fall is responsible for maintaining near-freezing subsurface temperatures in this northwest Pacific marginal sea as well as relatively stable temperatures and salinities at depths below a shallow subsurface temperature minimum. During periods in the late Pleistocene, high C. davisiana abundances (>20%) in the North Atlantic were probably associated with oceanographic properties similar to those that exist in the Sea of Okhotsk today. Because of the relationship between relatively stable subsurface temperatures and salinities and high abundance levels of C. davisiana, analysis of this species' abundance pattern at several locations throughout the high-latitude North Atlantic should assist in identifying source areas of deep-water formation and determining the duration of deep convective processes at these sites.

Phylogenetic relationships of Polysiphonia (Rhodomelaceae, Rhodophyta) and its relatives based on anatomical and nuclear small-subunit rDNA sequence data

2001 ◽  
Vol 79 (12) ◽  
pp. 1465-1476 ◽  
Author(s):  
Han-Gu Choi ◽  
Myung-Sook Kim ◽  
Michael D Guiry ◽  
Gary W Saunders
Keyword(s):  
North Atlantic ◽  
Sequence Data ◽  
Small Subunit ◽  
Total Evidence ◽  
Northwest Pacific ◽  
Diagnostic Features ◽  
Dna Sequence Data ◽  
The North ◽  
Small Subunit Rdna ◽  
The North Atlantic

The aim of this study was to reassess monophyly of the genus Polysiphonia and determine the phylogenetic affinities of its component lineages among related red algae belonging to the Rhodomelaceae. Our "total evidence" approach, combining 28 anatomical characters and small-subunit ribosomal DNA sequence data for 25 ceramialean algae including 14 species of Polysiphonia sensu lato (including two species of the recently described genus Neosiphonia) and nine related Rhodomelaceae, indicates that Polysiphonia sensu lato consists of three strongly supported clades, Polysiphonia group, Neosiphonia group, and a "multipericentral" group, and a single taxon lineage consisting of Womersleyella setacea. The type species of the genus, Polysiphonia urceolata (= Polysiphonia stricta) from the north Atlantic, formed a distinct clade with Polysiphonia morrowii and Polysiphonia pacifica from the northwest and northeast Pacific, respectively. The Neosiphonia group included Neosiphonia japonica and Neosiphonia savatieri from the northwest Pacific, as originally proposed, Polysiphonia harveyi from the north Atlantic, which shares diagnostic features with this genus, and the anomalous Polysiphonia elongata and Polysiphonia virgata from the north Atlantic and South Africa, respectively. Boergeseniella and Vertebrata from the north Atlantic and Enelittosiphonia from the northwest Pacific associated solidly with the multipericentral Polysiphonia fucoides and Polysiphonia nigra from the north Atlantic. The implications for the taxonomy of Polysiphonia sensu lato and related genera within the Rhodomelaceae are discussed.Key words: Neosiphonia, nuclear small-subunit rDNA, phylogeny, Polysiphonia, Rhodomelaceae, Rhodophyta, systematics.

scholarly journals Subsurface North Atlantic warming as a trigger of rapid cooling events: evidence from the early Pleistocene (MIS 31–19)

2015 ◽  
Vol 11 (4) ◽  
pp. 687-696 ◽  
Author(s):  
I. Hernández-Almeida ◽  
F.-J. Sierro ◽  
I. Cacho ◽  
J.-A. Flores
Keyword(s):  
Water Column ◽  
Carbon Isotopes ◽  
North Atlantic ◽  
Planktonic Foraminifera ◽  
Meridional Overturning Circulation ◽  
Early Pleistocene ◽  
Subsurface Water ◽  
The North ◽  
The North Atlantic ◽  
Subsurface Temperatures

Abstract. Subsurface water column dynamics in the subpolar North Atlantic were reconstructed in order to improve the understanding of the cause of abrupt ice-rafted detritus (IRD) events during cold periods of the early Pleistocene. We used paired Mg / Ca and δ18O measurements of Neogloboquadrina pachyderma (sinistral – sin.), deep-dwelling planktonic foraminifera, to estimate the subsurface temperatures and seawater δ18O from a sediment core from Gardar Drift, in the subpolar North Atlantic. Carbon isotopes of benthic and planktonic foraminifera from the same site provide information about the ventilation and water column nutrient gradient. Mg / Ca-based temperatures and seawater δ18O suggest increased subsurface temperatures and salinities during ice-rafting, likely due to northward subsurface transport of subtropical waters during periods of weaker Atlantic Meridional Overturning Circulation (AMOC). Planktonic carbon isotopes support this suggestion, showing coincident increased subsurface ventilation during deposition of IRD. Subsurface accumulation of warm waters would have resulted in basal warming and break-up of ice-shelves, leading to massive iceberg discharges in the North Atlantic. The release of heat stored at the subsurface to the atmosphere would have helped to restart the AMOC. This mechanism is in agreement with modelling and proxy studies that observe a subsurface warming in the North Atlantic in response to AMOC slowdown during Marine Isotope Stage (MIS) 3.

scholarly journals Dominant Modes of China Summer Heat Waves Driven by Global Sea Surface Temperature and Atmospheric Internal Variability

2019 ◽  
Vol 32 (12) ◽  
pp. 3761-3775 ◽  
Author(s):  
Kaiqiang Deng ◽  
Song Yang ◽  
Mingfang Ting ◽  
Ping Zhao ◽  
Zunya Wang
Keyword(s):  
North Atlantic ◽  
High Pressures ◽  
Heat Waves ◽  
Southern China ◽  
Wave Train ◽  
Internal Variability ◽  
Northwest Pacific ◽  
The North ◽  
Summer Heat ◽  
The North Atlantic

AbstractThis study applies the maximum temperatures at more than 2000 Chinese stations to investigate the dominant modes of China summer heat waves (HWs). The first empirical orthogonal function (EOF) mode of the HW days reflects an increased frequency of HWs in northern China (NC), while the second and third modes represent two distinct interannual modes, with key regions over the Yangtze River valley (YRV) and southern China (SC), respectively. The NC HWs are possibly associated with the Atlantic–Eurasian teleconnection, showing zonally propagating wave trains over the North Atlantic and Eurasian continent. The YRV HWs are proposed to be linked to the North Atlantic Oscillation, which may trigger a southeastward-propagating wave train over northern Russia and East Asia that results in a high pressure anomaly over the YRV. The SC HWs are obviously dominated by the Indian Ocean and northwest Pacific warm SSTs owing to the transition from the preceding El Niño to La Niña, which excites above-normal highs over SC. The anomalously high pressures over NC, the YRV, and SC are usually accompanied by descending air motions, clear skies, decreased precipitation, and increased solar radiation, which jointly cause a drier and hotter soil condition that favors the emergence of HWs. The GFDL HiRAM experiments are able to reproduce the historical evolution of NC and SC HWs, but fail to capture the YRV HWs. The correlation coefficient between model PC1 (PC2) and observed PC1 (PC3) for the period of 1979–2008 is 0.65 (0.38), which significantly exceeds the 95% (90%) confidence level, indicating that this model has a more faithful representation for the SST-forced HWs.

Reversed Magnetozone in the Late Pleistocene Sediments from the Pacific Coast of Odaka, Northeast Japan

1977 ◽  
Vol 7 (3) ◽  
pp. 372-379 ◽  
Author(s):  
Ken-Ichi Manabe
Keyword(s):  
Late Pleistocene ◽  
North Atlantic ◽  
Deep Sea ◽  
Pacific Coast ◽  
Marine Terrace ◽  
The North ◽  
The Pacific ◽  
The North Atlantic ◽  
Sea Cliff ◽  
Peak Field

Paleomagnetic measurements have been carried out on 103 specimens taken at about 15 cm intervals in a sea cliff exposing the marine terrace formation. Secondary components were removed by partial demagnetization in a peak field of 200 Oe. Two short reversed magnetozones are recognized. Geological and biostratigraphical evidence indicates that they are equivalent to the Blake event, which was first reported by Smith and Foster (1969) (Science 163 , 565–567) from the North Atlantic deep-sea cores. The present result suggests a split nature for the Blake Event.

Spectral Analysis of Late Pleistocene-Holocene Sediments

1973 ◽  
Vol 3 (1) ◽  
pp. 3-9 ◽  
Author(s):  
Nicklas G. Pisias ◽  
J.Paul Dauphin ◽  
Constance Sancetta
Keyword(s):  
Spectral Analysis ◽  
Late Pleistocene ◽  
North Atlantic ◽  
Deep Sea ◽  
Significant Peak ◽  
The North ◽  
Holocene Sediments ◽  
Deep Sea Sediments ◽  
The North Atlantic ◽  
Random Fluctuations

AbstractSpectral analysis of deep-sea sediments indicates that the fluctuations in compositional parameters are not random fluctuations with time. Spectra show significant peaks representing periodicities in the data of 380, 1300, and 2600 years. Two of these periods are similar to periods reported in 14C fluctuations. Analysis of a paleotemperature curve from the North Atlantic shows that the characteristics of the fluctuations within interglacial and glacial stages of the climate are similar, and that the spectrum has a significant peak at 2600 years.

scholarly journals Climate‐Induced Variability in Mediterranean Outflow to the North Atlantic Ocean During the Late Pleistocene

2020 ◽  
Vol 35 (9) ◽  
Author(s):  
Matthew D. Nichols ◽  
Chuang Xuan ◽  
Simon Crowhurst ◽  
David A. Hodell ◽  
Carl Richter ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Late Pleistocene ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
The North ◽  
Mediterranean Outflow ◽  
The North Atlantic

scholarly journals Stationary Waves and Upward Troposphere-Stratosphere Coupling in S2S Models

2021 ◽  
Author(s):  
Chen Schwartz ◽  
Chaim I. Garfinkel ◽  
Priyanka Yadav ◽  
Wen Chen ◽  
Daniela Domeisen
Keyword(s):  
North Atlantic ◽  
Strong Relationship ◽  
Stationary Wave ◽  
Northwest Pacific ◽  
Stationary Waves ◽  
Western North America ◽  
Model Errors ◽  
The North ◽  
The North Atlantic ◽  
The Waves

Abstract. The simulated Northern Hemisphere stationary wave (SW) field is investigated in 11 subseasonal-to-seasonal (S2S) models. It is shown that while most models considered can well-simulate the stationary wavenumbers 1 and 2 during the first two weeks of integration, they diverge from observations following week 3. Those models with a poor resolution in the stratosphere struggle to simulate the waves, both in the troposphere and the stratosphere, even during the first two weeks, and biases extend from the troposphere all the way up to the stratosphere. Focusing on the tropospheric regions where SWs peak in amplitude reveals that the models generally do a better job in simulating the Northwest Pacific stationary trough, while certain models struggle to simulate the stationary ridges both in Western North America and the North Atlantic. In addition, a strong relationship is found between regional biases in the stationary height field and model errors in simulated upward propagation of planetary waves into the stratosphere. In the stratosphere, biases mostly are in wave-2 in those models with high stratospheric resolution, whereas in those models with low resolution in the stratosphere, a wave-1 bias is evident, which leads to a strong bias in the stratospheric mean zonal circulation due to the predominance of wave-1 there. Finally, biases in both amplitude and location of mean tropical convection and the subsequent subtropical downwelling, are identified as possible contributors to biases in the regional SW field in the troposphere.

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