scholarly journals A simple conceptual model of abrupt glacial climate events

2007 ◽  
Vol 14 (6) ◽  
pp. 709-721 ◽  
Author(s):  
H. Braun ◽  
A. Ganopolski ◽  
M. Christl ◽  
D. R. Chialvo
Keyword(s):  
Conceptual Model ◽  
Stochastic Resonance ◽  
Statistical Significance ◽  
Nonlinear Resonance ◽  
Characteristic Time Scale ◽  
The North ◽  
The Stability ◽  
Climate Events ◽  
Threshold Process ◽  
Glacial Climate

Abstract. Here we use a very simple conceptual model in an attempt to reduce essential parts of the complex nonlinearity of abrupt glacial climate changes (the so-called Dansgaard-Oeschger events) to a few simple principles, namely (i) the existence of two different climate states, (ii) a threshold process and (iii) an overshooting in the stability of the system at the start and the end of the events, which is followed by a millennial-scale relaxation. By comparison with a so-called Earth system model of intermediate complexity (CLIMBER-2), in which the events represent oscillations between two climate states corresponding to two fundamentally different modes of deep-water formation in the North Atlantic, we demonstrate that the conceptual model captures fundamental aspects of the nonlinearity of the events in that model. We use the conceptual model in order to reproduce and reanalyse nonlinear resonance mechanisms that were already suggested in order to explain the characteristic time scale of Dansgaard-Oeschger events. In doing so we identify a new form of stochastic resonance (i.e. an overshooting stochastic resonance) and provide the first explicitly reported manifestation of ghost resonance in a geosystem, i.e. of a mechanism which could be relevant for other systems with thresholds and with multiple states of operation. Our work enables us to explicitly simulate realistic probability measures of Dansgaard-Oeschger events (e.g. waiting time distributions, which are a prerequisite for statistical analyses on the regularity of the events by means of Monte-Carlo simulations). We thus think that our study is an important advance in order to develop more adequate methods to test the statistical significance and the origin of the proposed glacial 1470-year climate cycle.

scholarly journals Recent Trends in the Recurrence of North Atlantic Atmospheric Circulation Patterns

Complexity ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Pascal Yiou ◽  
Julien Cattiaux ◽  
Aurélien Ribes ◽  
Robert Vautard ◽  
Mathieu Vrac
Keyword(s):  
Atmospheric Circulation ◽  
North Atlantic ◽  
Atmospheric Circulation Patterns ◽  
The North ◽  
Emerging Trends ◽  
Circulation Patterns ◽  
Long Term Trends ◽  
Recent Trends ◽  
The Stability ◽  
Climate Events

A few types of extreme climate events in the North Atlantic region, such as heatwaves, cold spells, or high cumulated precipitation, are connected to the recurrence of atmospheric circulation patterns. Understanding those extreme events requires assessing long-term trends of the atmospheric circulation. This paper presents a set of diagnostics of the intra- and interannual recurrence of atmospheric patterns. Those diagnostics are devised to detect trends in the stability of the circulation and the return period of atmospheric patterns. We detect significant emerging trends in the winter circulation, pointing towards a potential increased predictability. No such signal seems to emerge in the summer. We find that the winter trends in the dominating atmospheric patterns and their recurrences do not depend of the patterns themselves.

Are Cryosphere-Driven Feedbacks a Requisite for Abrupt Climate Events? (Site U610, DSDP Leg. 94)

2021 ◽  
Author(s):  
Dakota Holmes ◽  
David De Vleeschouwer ◽  
Audrey Morley
Keyword(s):  
Meridional Overturning Circulation ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
North Atlantic Current ◽  
Planktic Foraminifera ◽  
Climate Change Research ◽  
The North ◽  
Depth Scale ◽  
Climate Events ◽  
Glacial Climate

<p>Abrupt climate events are important features of glacial climate scales on centennial and millennial timescales. These events' mechanistic trigger is often ascribed to either ice sheet-related feedback mechanisms or large freshwater pulses. In both cases, amplification occurs when these triggers bear upon the Atlantic Meridional Overturning Circulation (AMOC). However, the focus on glacial climate states in abrupt climate change research has led to an underrepresentation of research into interglacial periods. It thus remains unclear whether high-magnitude climate variability requires large cryosphere-driven feedbacks or whether it can also occur under low ice conditions. Using sediment core DSDP U610B (53°13.297N, 18°53.213W) located in the Rockall Trough, we present a high-resolution analysis of surface and deep water components of the AMOC spanning the transition from Marine Isotope Stage (MIS) 19.3 to 19.1 to test if orbital boundary conditions similar to our current Holocene can accommodate abrupt climate events. Above the core site, the dominant oceanographic feature is the North Atlantic Current and at 2417-m water depth, U610 is influenced by Wyville Thomson Overflow Water flowing southwards. We utilise a multiproxy approach including paired grain size analysis, planktic foraminifera assemblage counts, and ice-rafted debris counts within the same samples allowing us to resolve the timing between both surface and bottom components of the AMOC and their response to abrupt climate events during MIS-19 in the eastern subpolar gyre. We also present for the first time a new splice and composite depth scale for Site U610. Based on preliminary results, rapid shifts in both deep overflow and surface climate characterise this period.</p>

An impact of intima media thickness of carotids in cardio vascular profile

2020 ◽  
Vol 10 (2) ◽  
pp. 48-52
Author(s):  
Jeevitha M ◽  
Kalaichandar M ◽  
Kirubakaran K ◽  
Baskaran V ◽  
Kokila K ◽  
...  
Keyword(s):  
Blood Pressure ◽  
High Blood Pressure ◽  
Statistical Significance ◽  
Intima Media Thickness ◽  
Cardio Vascular ◽  
Intima Medial Thickness ◽  
The Stability ◽  
Carotid Intima Medial Thickness ◽  
Oral Sodium ◽  
Worse Prognosis

Low blood pressure truly includes a worse prognosis than the excessive blood strain. This mechanism,bills for the "reverse causation "seen within the haemodialysis’ patients, the company of conventional risk elements, such as high blood pressure, hyperlipidemia, and obesity, appear to be a worst diagnosis.Exogenous erythropoietic products can growth blood strain and requirement of antihypertensive tablets.30 Chronic ECFV overload secondary to activation of renin-angiotensin-aldosterone axisand disturbances inside the stability of vasoconstrictors and the vasodilators make a contribution to high blood pressure. Improvement in blood pressure can be introduced out with oral sodium restriction, diuretics, and fluid elimination with dialysis. Some patients will continue to be hypertensive notwithstanding of the careful attention to ECFV reputation. LVH is related with reduced endurance of sufferers on hemo/peritoneal dialysis .Lower five year survival charge in ESRD patients with LVH have a 30% than people missing LVH. This have a look at produces the mean carotid artery intima-medial thickness turned into higher in sufferers with superior CKD although it did now not attain statistical significance, probable due to smaller sample size.It was also observed that carotid intima medial thickness had no correlation with dyslipidemia. Even though the patients had maintained significantly normal cholesterol and high HDL levels, there was an increase in CIMT. Therefore, CKD patients, CIMT cannot be predicted based on the traditional atherosclerotic risk factors like serum cholesterol and HDL.

Assessing the temporal reliability of rhythm metrics

2011 ◽  
Vol 41 (3) ◽  
pp. 271-281 ◽  
Author(s):  
Rachael-Anne Knight
Keyword(s):  
Current Paper ◽  
Empirical Measure ◽  
The Sun ◽  
British English ◽  
The North ◽  
North Wind ◽  
The Stability ◽  
Current Popularity ◽  
Temporal Reliability

Despite the current popularity of rhythm metrics, there has been relatively little work aimed at establishing their validity or reliability, important characteristics of any empirical measure. The current paper focuses on the stability, or temporal reliability, of rhythm metrics by establishing if they give consistent results for the same speakers, in the same task, on successive occasions. Four speakers of Southern British English were recorded reading ‘The North Wind and the Sun’ (NWS) passage on three consecutive days. Results indicated that some measures correlate more highly across time than others, and the choice of a measure that is both reliable and valid is discussed. It is suggested that the metric that best fits these criteria is formulated in terms of the proportion of vowels within an utterance (%V).

scholarly journals Patterns of millennial variability over the last 500 ka

2010 ◽  
Vol 6 (3) ◽  
pp. 295-303 ◽  
Author(s):  
M. Siddall ◽  
E. J. Rohling ◽  
T. Blunier ◽  
R. Spahni
Keyword(s):  
Atmospheric Circulation ◽  
North Atlantic ◽  
Glacial Cycles ◽  
The North ◽  
The North Atlantic ◽  
Paleoclimate Records ◽  
Temperature Proxy ◽  
Freshwater Release ◽  
Glacial Periods ◽  
Climate Events

Abstract. Millennial variability is a robust feature of many paleoclimate records, at least throughout the last several glacial cycles. Here we use the mean signal from Antarctic climate events 1 to 4 to probe the EPICA Dome C temperature proxy reconstruction through the last 500 ka for similar millennial-scale events. We find that clusters of millennial events occurred in a regular fashion over half of the time during this with a mean recurrence interval of 21 kyr. We find that there is no consistent link between ice-rafted debris deposition and millennial variability. Instead we speculate that changes in the zonality of atmospheric circulation over the North Atlantic form a viable alternative to freshwater release from icebergs as a trigger for millennial variability. We suggest that millennial changes in the zonality of atmospheric circulation over the North Atlantic are linked to precession via sea-ice feedbacks and that this relationship is modified by the presence of the large, Northern Hemisphere ice sheets during glacial periods.

scholarly journals A new conceptual model of coral biomineralisation: hypoxia as the physiological driver of skeletal extension

2013 ◽  
Vol 10 (5) ◽  
pp. 2867-2884 ◽  
Author(s):  
S. Wooldridge
Keyword(s):  
Conceptual Model ◽  
Multiple Scales ◽  
High Growth ◽  
High Growth Rate ◽  
Coral Host ◽  
Structural Determinants ◽  
Night Time ◽  
Long Run ◽  
Animal Phyla ◽  
The Stability

Abstract. That corals skeletons are built of aragonite crystals with taxonomy-linked ultrastructure has been well understood since the 19th century. Yet, the way by which corals control this crystallization process remains an unsolved question. Here, I outline a new conceptual model of coral biomineralisation that endeavours to relate known skeletal features with homeostatic functions beyond traditional growth (structural) determinants. In particular, I propose that the dominant physiological driver of skeletal extension is night-time hypoxia, which is exacerbated by the respiratory oxygen demands of the coral's algal symbionts (= zooxanthellae). The model thus provides a new narrative to explain the high growth rate of symbiotic corals, by equating skeletal deposition with the "work-rate" of the coral host needed to maintain a stable and beneficial symbiosis. In this way, coral skeletons are interpreted as a continuous (long-run) recording unit of the stability and functioning of the coral–algae endosymbiosis. After providing supportive evidence for the model across multiple scales of observation, I use coral core data from the Great Barrier Reef (Australia) to highlight the disturbed nature of the symbiosis in recent decades, but suggest that its onset is consistent with a trajectory that has been followed since at least the start of the 1900s. In concluding, I outline how the proposed capacity of cnidarians (which includes modern reef corals) to overcome the metabolic limitation of hypoxia via skeletogenesis also provides a new hypothesis to explain the sudden appearance in the fossil record of calcified skeletons at the Precambrian–Cambrian transition – and the ensuing rapid appearance of most major animal phyla.

scholarly journals Indonesia's Diplomacy in North Natuna Sea in Confronting China to Protect National Interests

FOCUS ◽  
2020 ◽  
Vol 1 (1) ◽  
pp. 21-27
Author(s):  
Gerald Theodorus Lumban Toruan ◽  
Adi Sunaryo
Keyword(s):  
Research Question ◽  
Secondary Data ◽  
Coast Guard ◽  
Regional Security ◽  
National Interests ◽  
The North ◽  
Fishing Vessels ◽  
Qualitative Descriptive ◽  
The Stability ◽  
The Right

North Natuna Sea is become a concern, at the end of 2019 to February 2020 this area was illegally entered by Chinese fishing vessels who wanted to fishing, this vessel was escorted by the Chinese Coast Guard. This escort is in order to protect their fishing vessels from the pursuit of Indonesian patrol vessels. According to the them that they did not violate Indonesian territory, they said that the North Natuna Sea still belongs to Chinese territory. In the perspective of the international relations what is done by China can disrupt the stability of regional security. This research is a qualitative descriptive with secondary data collection. The formulation of the research question is what kind of diplomacy is being carried out by Indonesia towards China in the North Natuna Sea. The purpose of this research is to find the right diplomacy concept in dealing with the China in the North Natuna Sea.

scholarly journals Irrational ideas and social fear among students of faculties of applied sciences in the Sultanate of Oman according to gender variables and academic specialization: الأفكار اللاعقلانية والخوف الاجتماعي لدى طلبة كليات العلوم التطبيقية بسلطنة عمان وفق متغيرات النوع الاجتماعي والتخصص الأكاديمي

2017 ◽  
Vol 1 (8) ◽  
Author(s):  
Nasra Muslim Hamad Al - Ghafri
Keyword(s):  
Applied Sciences ◽  
Statistical Significance ◽  
Sultanate Of Oman ◽  
Social Scale ◽  
The Social ◽  
Social Fear ◽  
The Stability ◽  
Academic Specialization

The aim of the study was to identify the level of the most irrational ideas among the students of faculties of applied sciences, to identify the level of social fear among the students of faculties of applied sciences and to identify whether there were statistically significant differences in the effect of the spread of irrational ideas and the level of social fear according to variables (The type of specialization). The population of the study included all the students of faculties of applied sciences in (Ibri-Nizwa-Rustaq), (4568). The sample of the study was chosen in the available way, with 282 students. Descriptive descriptive in This study was developed as a tool to measure irrational ideas and a tool was developed to measure social fear. The validity of the tools was verified through the method of arbitration. The stability of the tool was estimated in the Alpha Kronbach method and the results showed that the two tools were acceptable and reliable. The degree of spread of irrational ideas among the students of faculties of applied sciences was medium, while the degree of spread of the level of social fear among students of faculties of applied sciences medium, and the results showed that there are no differences of statistical significance according to variables of type and specialization of the scale of ideas not Qlanah results also showed that there were no statistically significant differences according to the variables of type and specialization of the social scale of fear ..

scholarly journals Criteria for evaluating the competencies of the school counselor at the basic education stage from the point of view of school principals in the state of Khartoum: معايير تقويم كفايات المرشد المدرسي بمرحلة تعليم الاساس من وجهة نظر مدراء المدارس بولاية الخرطوم

2017 ◽  
Vol 1 (3) ◽  
Author(s):  
Ikhlas Hassan Sayyid Echriya ◽  
Reham Anwar Mohammed Hassan
Keyword(s):  
School Counselor ◽  
Basic Education ◽  
School Principals ◽  
Pearson Correlation ◽  
Statistical Significance ◽  
Correlation Equation ◽  
Significance Test ◽  
Point Of View ◽  
The Stability ◽  
Extension Process

The aim of this study was to investigate the criteria of evaluating the competencies of the school counselor in the basic education stage, from the point of view of the school principals in Khartoum State, to achieve the objectives of the study. The researchers prepared a questionnaire that was applied during the academic year 2014-2015 to a random sample of 20 managers in basic education Khartoum, a maritime locality, the questionnaire contains six criteria for evaluating the school's competencies: planning the extension process, implementing the extension process, designing the extension programs, effective communication skills, using the technique in the extension process, In order to ascertain the stability and validity of the questionnaire, by means of the Alpha Kronbach equation and to verify the persistence of the questionnaire by Pearson correlation equation for the questionnaire items in the overall degree of the questionnaire, the sincerity of the arbitrators was measured by presenting it to a number of curriculum experts and pedagogic and educational psychologists in different Sudanese universities. Statistical packages of social sciences (SPSS), and statistical methods used to analyze repetitive data: percentages, arithmetical averages, standard deviations, mono variance, applied statistical significance test (T) The results of the study were reached by a number of recommendations, the most important of which are the need to develop an integrated methodology and a clear job description. For the role of the educational guide, and the process of educational guidance of schools based on the academic procedures of higher education, the need to contribute sections of educational psychology in the quality models and procedures to control and follow up the implementation of strategic plans for the tasks of the school guide and evaluate, The number of educational counselors for the number of learners and the creation of the guiding environment.

scholarly journals Hydrogeological Conceptual Model in the Middle of Randublatung Groundwater Basin

2021 ◽  
Vol 926 (1) ◽  
pp. 012078
Author(s):  
D L Setyaningsih ◽  
K D Setyawan ◽  
D P E Putra ◽  
Salahuddin
Keyword(s):  
Groundwater Flow ◽  
Conceptual Model ◽  
Unconfined Aquifer ◽  
Primary Data ◽  
Essential Information ◽  
Aquifer System ◽  
The North ◽  
Shallow Wells ◽  
Groundwater Basin ◽  
Constant Head

Abstract Randublatung groundwater basin is one of the groundwaters basins with massive utilization of groundwater pumping. However, the knowledge of the comprehensive hydrogeological system in this groundwater basin is limited, so this research aims to determine a comprehensive hydrogeological conceptual model of the Randublatung groundwater basin. The methodology was conducted by collecting secondary and primary data of deep and shallow wells to evaluate boundaries of pattern and direction of groundwater flow and develop the aquifer system’s geometry. The result shows that the groundwater flow boundaries are Grogol River in the west, Wado River in the East, Bengawan Solo river in the South as a river boundary, and Rembang Mountains in the North as a constant head boundary. Therefore, groundwater flows from the hills area to the Bengawan Solo River and the north as the river’s flow. Based on the log bor evaluation, the aquifer system of the study area consist of an unconfined aquifer with a maximum thickness of 20 m and three layers of confined aquifers with thickness vary between 8 to 60 m. the hydraulic conductivity of the aquifers depends on the aquifer’s lithology range from sand, gravel, limestone, and sandstone. This hydrogeological conceptual model provides essential information for numerical groundwater models in the middle of the Randublatung groundwater basin.

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