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 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.

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.

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.

Explosive Cyclogenesis: A Global Climatology Comparing Multiple Reanalyses

2010 ◽  
Vol 23 (24) ◽  
pp. 6468-6484 ◽  
Author(s):  
John T. Allen ◽  
Alexandre B. Pezza ◽  
Mitchell T. Black
Keyword(s):  
North Atlantic ◽  
Reanalysis Data ◽  
Formative Period ◽  
Northwest Pacific ◽  
The North ◽  
Explosive Cyclones ◽  
The North Atlantic ◽  
Positive Correlations ◽  
Almost All ◽  
Interseasonal Variability

Abstract A global climatology for rapid cyclone intensification has been produced from the second NCEP reanalysis (NCEP2), the 25-yr Japanese Reanalysis (JRA-25), and the ECMWF reanalyses over the period 1979–2008. An improved (combined) criterion for identifying explosive cyclones has been developed based on preexisting definitions, offering a more balanced, normalized climatological distribution. The combined definition was found to significantly alter the population of explosive cyclones, with a reduction in “artificial” systems, which are found to compose 20% of the population determined by earlier definitions. Seasonally, winter was found to be the dominant formative period in both hemispheres, with a lower degree of interseasonal variability in the Southern Hemisphere (SH). Considered over the period 1979–2008, little change is observed in the frequency of systems outside of natural interannual variability in either hemisphere. Significant statistical differences have been found between reanalyses in the SH, while in contrast the Northern Hemisphere (NH) was characterized by strong positive correlations between reanalyses in almost all examined cases. Spatially, explosive cyclones are distributed into several distinct regions, with two regions in the northwest Pacific and the North Atlantic in the NH and three main regions in the SH. High-resolution and modern reanalysis data were also found to increase the climatology population of rapidly intensifying systems. This indicates that the reanalyses have apparently undergone increasing improvements in consistency over time, particularly in the SH.

The Currents of the North Atlantic

1892 ◽  
Vol 34 (872supp) ◽  
pp. 13940-13941
Author(s):  
Richard Beynon
Keyword(s):  
North Atlantic ◽  
The North ◽  
The North Atlantic

NATO adaptation to current challenges and mechanisms of Ukraine’s cooperation with the North Atlantic Treaty Organization

2019 ◽  
pp. 73-81
Author(s):  
Oleh Poshedin
Keyword(s):  
North Atlantic ◽  
Task Force ◽  
Response Force ◽  
Cyber Attack ◽  
Adaptation Measures ◽  
Joint Force ◽  
Security Environment ◽  
The North ◽  
The North Atlantic ◽  
Area Of Influence

The purpose of the article is to describe the changes NATO undergoing in response to the challenges of our time. Today NATO, as a key element of European and Euro-Atlantic security, is adapting to changes in the modern security environment by increasing its readiness and ability to respond to any threat. Adaptation measures include the components required to ensure that the Alliance can fully address the security challenges it might face. Responsiveness NATO Response Force enhanced by developing force packages that are able to move rapidly and respond to potential challenges and threats. As part of it, was established a Very High Readiness Joint Task Force, a new Allied joint force that deploy within a few days to respond to challenges that arise, particularly at the periphery of NATO’s territory. NATO emphasizes, that cyber defence is part of NATO’s core task of collective defence. A decision as to when a cyber attack would lead to the invocation of Article 5 would be taken by the North Atlantic Council on a case-by-case basis. Cooperation with NATO already contributes to the implementation of national security and defense in state policy. At the same time, taking into account that all decision-making in NATO based on consensus, Ukraine’s membership in the Alliance quite vague perspective. In such circumstances, in Ukraine you often can hear the idea of announcement of a neutral status. It is worth reminding that non-aligned status did not save Ukraine from Russian aggression. Neutral status will not accomplish it either. All talks about neutrality and the impossibility of Ukraine joining NATO are nothing but manipulations, as well as recognition of the Ukrainian territory as Russian Federation area of influence (this country seeks to sabotage the Euro-Atlantic movement of Ukraine). Think about it, Moldova’s Neutrality is enshrined in the country’s Constitution since 1994. However, this did not help Moldova to restore its territorial integrity and to force Russia to withdraw its troops and armaments from Transnistria.

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