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1.
Int J Speech Lang Pathol ; : 1-16, 2023 Sep 20.
Article in English | MEDLINE | ID: mdl-37729082

ABSTRACT

PURPOSE: Echolalia, the repetition of previously heard speech, is prevalent in a variety of neurologic and psychiatric disorders. Within the context of echolalia in autism spectrum disorder (ASD), research and intervention historically assume a clinical standpoint with two opposing paradigms: behaviourism and developmentalism. The literature is largely silent on how those other than researchers and clinicians understand echolalia. This study examined how parents experience echolalia through their children with ASD. The aim of the study was to ascertain if the parental perception of echolalia in ASD aligns with, or offers alternative perspectives to, current clinically-orientated views. METHOD: We employed online semi-structured interviews to document the experiences of 126 parents, reflecting on their children with ASD aged 3 to 34 years of age, to determine if the parent experience could be mapped onto existing clinical frameworks, or if they might offer new perspectives. We used hermeneutic phenomenological data analysis in an abductive framework. RESULT: Echolalia has predominantly been represented in literature through the perspectives of behaviourism or developmentalism. We found however, that echolalia is a phenomenon that is experienced by parents in a variety of different ways to that of the current clinically-orientated understandings. Such new ways of understanding echolalia that emerged from our analysis include one understanding which is dependent upon how echolalia is heard, and one in which parents are "waiting for echolalia to evolve." CONCLUSION: The traditional dichotomous clinical positions do not resonate with all parents, and reliance on these traditional perspectives alone may impact effective engagement with parents and the success of interventions and support strategies. Our findings have implications for future research, the education of clinicians and educators, and the design of support and intervention for those who have echolalia.

2.
Autism ; : 13623613231195795, 2023 Sep 06.
Article in English | MEDLINE | ID: mdl-37674319

ABSTRACT

LAY ABSTRACT: Echolalia is a commonly found speech and language condition in autistic children. Children with echolalia repeat words and phrases they previously hear in place of proving a non-repetitive response. In research and when visiting speech and language services, one of the common goals is to modify these repetitions so that these children may, more socially, engage with their surrounding environment. In our research, we identified that not all parents want their children's echolalia to be modified. Some parents want their child to be able to enjoy echolalia and others don't want anyone to intervene because they see it as something that makes their child unique and being unique is something to be celebrated. We believe that there might be a way for speech and language services who want to modify echolalia and the parents in our study who do not want their child's echolalia to be modified, to be able to exist side-by-side.

3.
Autism Dev Lang Impair ; 8: 23969415231151846, 2023.
Article in English | MEDLINE | ID: mdl-36726967

ABSTRACT

Backgrounds and aims: Echolalia, the repetition of previous speech, is highly prevalent in Autism. Research into echolalia has historically assumed a clinical standpoint, with two opposing paradigms, behaviourism and developmentalism, offering differing support and intervention programs. These paradigms offer a multitude of clinical operationalised definitions; despite attempts, there continue to be challenges regarding how echolalia is to be defined. Stepping out of the dichotomous clinically orientated literature, we examined how parents summarise and formalise their understanding of echolalia as a communication partner. The objectives of this study were three-fold: (1) to investigate how echolalia is described and defined by parents; (2) to examine if existing clinical definitions align with those of parents; and (3) to begin to consider the implications of such findings for a collaborative approach between clinical perspectives and the parent experience. We bring to the fore the voices of parents, who have historically remained absent from echolalia literature. That is to say, we step outside of the clinical realm and listen to parents: something which has been previously unconsidered but represents a new vital addition to the echolalia literature. Methods: We employed a Grounded Theory approach to document the definitions of 133 parents. Results: We found that parents reported a multiplicity of important elements that are key to their understanding of echolalia. Conclusions and implications: Additionally, we found that clinical definitions do not resonate within the parent experience; parents experience echolalia in a different way to that of clinicians and parents can offer insight into our understanding of the phenomena. Our findings show that while some parents might align themselves with either a behavioural or developmental positionality, sometimes there is an overlap depending upon the context in which their child repeats and some parents advance interpretations that are not readily aligned with either of the traditional clinical schools of thought. We present implications for both clinicians and parents in ways that point towards a collaborative approach to support the person with echolalia.

4.
Autism Dev Lang Impair ; 7: 23969415221091928, 2022.
Article in English | MEDLINE | ID: mdl-36382082

ABSTRACT

Background and Aims: Echolalia, the repetition of speech, is highly prevalent in school aged children with Autism. Prior research has found that individuals with echolalia use their repetitions to engage in communicatively functional speech, in the absence of self-generated speech. Educators are the natural audience for a wide vary of echoed utterances across environments and in differing contexts. The objectives of this paper were three-fold: (1) to systematically investigate how researchers identify and ascribe communicative function to echoed utterances; (2) to gather and evaluate the evidence that might assist teachers to identify and better understand echoed utterances as being communicatively purposeful; and (3) to provide teachers with evidence-informed response strategies they can use to assist their students on their journey towards more self-generated speech. Main Contribution: Prior research in the field of echolalia has generally been segmented into opposing viewpoints. A paucity of work in the echolalia field has meant that there is limited work that has sought to view how a communicative function to echolalia has been ascribed from across multiple disciplines and fields. As such, there is limited literature to guide the practice of classroom educators. This review combines communicative models from across various disciplines with the view to supporting classroom educators by providing guidance on how they might assist their students with echolalia. This review represents the first contribution to the research literature in this area. Conclusions and Implications: Research into echolalia did not originally emanate from the field of education; however, anecdotes from classroom educators were cited as the primary impetus for the creation of some of the communicatively functional models. We found that although there are many techniques that researchers have used to attribute a communicative function to echolalia, some of these can be easily employed by educators in their practice. By adopting these techniques, educators are placed in a position that may assist with the identification of communicative echolalia; subsequently they are better placed to acknowledge and respond to their students.

5.
JMIR Aging ; 4(3): e27047, 2021 Aug 11.
Article in English | MEDLINE | ID: mdl-34383672

ABSTRACT

BACKGROUND: As life expectancy grows, so do the challenges of caring for an aging population. Older adults, including people with dementia, want to live independently and feel in control of their lives for as long as possible. Assistive technologies powered by artificial intelligence and internet of things devices are being proposed to provide living environments that support the users' safety, psychological, and medical needs through remote monitoring and interventions. OBJECTIVE: This study investigates the functional, psychosocial, and environmental needs of people living with dementia, their caregivers, clinicians, and health and social care service providers toward the design and implementation of smart home systems. METHODS: We used an iterative user-centered design approach comprising 9 substudies. First, semistructured interviews (9 people with dementia, 9 caregivers, and 10 academic and clinical staff) and workshops (35 pairs of people with dementia and caregivers, and 12 health and social care clinicians) were conducted to define the needs of people with dementia, home caregivers, and professional stakeholders in both daily activities and technology-specific interactions. Then, the spectrum of needs identified was represented via patient-caregiver personas and discussed with stakeholders in a workshop (14 occupational therapists; 4 National Health Service pathway directors; and 6 researchers in occupational therapy, neuropsychiatry, and engineering) and 2 focus groups with managers of health care services (n=8), eliciting opportunities for innovative care technologies and public health strategies. Finally, these design opportunities were discussed in semistructured interviews with participants of a smart home trial involving environmental sensors, physiological measurement devices, smartwatches, and tablet-based chatbots and cognitive assessment puzzles (10 caregivers and 2 people with dementia). A thematic analysis revealed factors that motivate household members to use these technologies. RESULTS: Outcomes of these activities include a qualitative and quantitative analysis of patient, caregiver, and clinician needs and the identification of challenges and opportunities for the design and implementation of remote monitoring systems in public health pathways. CONCLUSIONS: Participatory design methods supported the triangulation of stakeholder perspectives to aid the development of more patient-centered interventions and their translation to clinical practice and public health strategy. We discuss the implications and limitations of our findings, the value and the applicability of our methodology, and directions for future research.

6.
Metabolomics ; 17(2): 14, 2021 01 18.
Article in English | MEDLINE | ID: mdl-33462674

ABSTRACT

INTRODUCTION: The Endosialin/CD248/TEM1 protein is expressed in adipose tissue and its expression increases with obesity. Recently, genetic deletion of CD248 has been shown to protect mice against atherosclerosis on a high fat diet. OBJECTIVES: We investigated the effect of high fat diet feeding on visceral fat pads and circulating lipid profiles in CD248 knockout mice compared to controls. METHODS: From 10 weeks old, CD248-/- and +/+ mice were fed either chow (normal) diet or a high fat diet for 13 weeks. After 13 weeks the metabolic profiles and relative quantities of circulating lipid species were assessed using ultra high performance liquid chromatography-quadrupole time-of flight mass spectrometry (UHPLC-MS) with high resolution accurate mass (HRAM) capability. RESULTS: We demonstrate a specific reduction in the size of the perirenal fat pad in CD248-/- mice compared to CD248+/+, despite similar food intake. More strikingly, we identify significant, diet-dependent differences in the serum metabolic phenotypes of CD248 null compared to age and sex-matched wildtype control mice. Generalised protection from HFD-induced lipid accumulation was observed in CD248 null mice compared to wildtype, with particular reduction noted in the lysophosphatidylcholines, phosphatidylcholines, cholesterol and carnitine. CONCLUSIONS: Overall these results show a clear and protective metabolic consequence of CD248 deletion in mice, implicating CD248 in lipid metabolism or trafficking and opening new avenues for further investigation using anti-CD248 targeting agents.


Subject(s)
Antigens, CD/genetics , Antigens, CD/metabolism , Chromatography, Liquid , Neoplasm Proteins/genetics , Neoplasm Proteins/metabolism , Tandem Mass Spectrometry , Adipose Tissue/metabolism , Animals , Antigens, Neoplasm , Carnitine/metabolism , Cholesterol , Chromatography, High Pressure Liquid , Diet, High-Fat , Female , Intra-Abdominal Fat/metabolism , Liver/metabolism , Male , Mice , Mice, Knockout , Obesity/metabolism , Phosphatidylcholines/metabolism , Transcriptome
7.
Haematologica ; 105(5): 1248-1261, 2020 05.
Article in English | MEDLINE | ID: mdl-31467123

ABSTRACT

Interactions between platelets, leukocytes and the vessel wall provide alternative pathological routes of thrombo-inflammatory leukocyte recruitment. We found that when platelets were activated by a range of agonists in whole blood, they shed platelet-derived extracellular vesicles which rapidly and preferentially bound to blood monocytes compared to other leukocytes. Platelet-derived extracellular vesicle binding to monocytes was initiated by P-selectin-dependent adhesion and was stabilised by binding of phosphatidylserine. These interactions resulted in the progressive transfer of the platelet adhesion receptor GPIbα to monocytes. GPIbα+-monocytes tethered and rolled on immobilised von Willebrand Factor or were recruited and activated on endothelial cells treated with TGF-ß1 to induce the expression of von Willebrand Factor. In both models monocyte adhesion was ablated by a function-blocking antibody against GPIbα. Monocytes could also bind platelet-derived extracellular vesicle in mouse blood in vitro and in vivo Intratracheal instillations of diesel nanoparticles, to model chronic pulmonary inflammation, induced accumulation of GPIbα on circulating monocytes. In intravital experiments, GPIbα+-monocytes adhered to the microcirculation of the TGF-ß1-stimulated cremaster muscle, while in the ApoE-/- model of atherosclerosis, GPIbα+-monocytes adhered to the carotid arteries. In trauma patients, monocytes bore platelet markers within 1 hour of injury, the levels of which correlated with severity of trauma and resulted in monocyte clearance from the circulation. Thus, we have defined a novel thrombo-inflammatory pathway in which platelet-derived extracellular vesicles transfer a platelet adhesion receptor to monocytes, allowing their recruitment in large and small blood vessels, and which is likely to be pathogenic.


Subject(s)
Blood Platelets , Extracellular Vesicles , Animals , Endothelial Cells , Humans , Inflammation , Mice , Monocytes , Platelet Glycoprotein GPIb-IX Complex
8.
J Cell Mol Med ; 22(9): 4317-4327, 2018 09.
Article in English | MEDLINE | ID: mdl-29974666

ABSTRACT

The Src family kinases (SFK) are a group of signalling molecules with important regulatory functions in inflammation and haemostasis. Leucocytes and platelets express multiple isoforms of the SFKs. Previous studies used broad-spectrum pharmacological inhibitors, or murine models deficient in multiple SFK isoforms, to demonstrate the functional consequences of deficiencies in SFK signalling. Here, we hypothesized that individual SFK operate in a non-redundant fashion in the thrombo-inflammatory recruitment of monocyte during atherosclerosis. Using in vitro adhesion assays and single SFK knockout mice crossed with the ApoE-/- model of atherosclerosis, we find that SFK signalling regulates platelet-dependent recruitment of monocytes. However, loss of a single SFK, Fgr or Lyn, reduced platelet-mediated monocyte recruitment in vitro. This translated into a significant reduction in the burden of atherosclerotic disease in Fgr-/- /ApoE-/- or Lyn-/- /ApoE-/- animals. SFK signalling is not redundant in thrombo-inflammatory vascular disease and individual SFK may represent targets for therapeutic intervention.


Subject(s)
Apolipoproteins E/genetics , Coronary Artery Disease/genetics , Monocytes/metabolism , Proto-Oncogene Proteins/genetics , src-Family Kinases/genetics , Animals , Aorta/metabolism , Aorta/pathology , Apolipoproteins E/deficiency , Cell Adhesion , Coronary Artery Disease/etiology , Coronary Artery Disease/metabolism , Coronary Artery Disease/pathology , Diet, High-Fat/adverse effects , Female , Gene Expression Regulation , Human Umbilical Vein Endothelial Cells/cytology , Human Umbilical Vein Endothelial Cells/metabolism , Humans , Male , Mice , Mice, Inbred C57BL , Mice, Knockout , Monocytes/pathology , Primary Cell Culture , Proto-Oncogene Proteins/deficiency , Signal Transduction , src-Family Kinases/deficiency
9.
J Immunol ; 198(7): 2834-2843, 2017 04 01.
Article in English | MEDLINE | ID: mdl-28193827

ABSTRACT

Two major monocyte subsets, CD14+CD16- (classical) and CD14+/dimCD16+ (nonclassical/intermediate), have been described. Each has different functions ascribed in its interactions with vascular endothelial cells (EC), including migration and promoting inflammation. Although monocyte subpopulations have been studied in isolated systems, their influence on EC and on the course of inflammation has been ignored. In this study, using unstimulated or cytokine-activated EC, we observed significant differences in the recruitment, migration, and reverse migration of human monocyte subsets. Associated with this, and based on their patterns of cytokine secretion, there was a difference in their capacity to activate EC and support the secondary recruitment of flowing neutrophils. High levels of TNF were detected in cocultures with nonclassical/intermediate monocytes, the blockade of which significantly reduced neutrophil recruitment. In contrast, classical monocytes secreted high levels of IL-6, the blockade of which resulted in increased neutrophil recruitment. When cocultures contained both monocyte subsets, or when conditioned supernatant from classical monocytes cocultures (IL-6hi) was added to nonclassical/intermediate monocyte cocultures (TNFhi), the activating effects of TNF were dramatically reduced, implying that when present, the anti-inflammatory activities of IL-6 were dominant over the proinflammatory activities of TNF. These changes in neutrophil recruitment could be explained by regulation of E-selectin on the cocultured EC. This study suggests that recruited human monocyte subsets trigger a regulatory pathway of cytokine-mediated signaling at the EC interface, and we propose that this is a mechanism for limiting the phlogistic activity of newly recruited monocytes.


Subject(s)
Chemotaxis, Leukocyte/immunology , Endothelial Cells/immunology , Inflammation/immunology , Monocytes/immunology , Signal Transduction/immunology , Cell Separation , Flow Cytometry , Humans , Interleukin-6/immunology , Polymerase Chain Reaction , Tumor Necrosis Factor-alpha/immunology
10.
Platelets ; 26(6): 507-20, 2015.
Article in English | MEDLINE | ID: mdl-26196409

ABSTRACT

Besides their role in the formation of thrombus during haemostasis, it is becoming clear that platelets contribute to a number of other processes within the vasculature. Indeed, the integrated function of the thrombotic and inflammatory systems, which results in platelet-mediated recruitment of leukocytes, is now considered to be of great importance in the propagation, progression and pathogenesis of atherosclerotic disease of the arteries. There are three scenarios by which platelets can interact with leukocytes: (1) during haemostasis, when platelets adhere to and are activated on sub-endothelial matrix proteins exposed by vascular damage and then recruit leukocytes to a growing thrombus. (2) Platelets adhere to and are activated on stimulated endothelial cells and then bridge blood borne leukocytes to the vessel wall and. (3) Adhesion between platelets and leukocytes occurs in the blood leading to formation of heterotypic aggregates prior to contact with endothelial cells. In the following review we will not discuss leukocyte recruitment during haemostasis, as this represents a physiological response to tissue trauma that can progress, at least in its early stages, in the absence of inflammation. Rather we will deal with scenarios 2 and 3, as these pathways of platelet-leukocyte interactions are important during inflammation and in chronic inflammatory diseases such as atherosclerosis. Indeed, these interactions mean that leukocytes possess means of adhesion to the vessel wall under conditions that may not normally be permissive of leukocyte-endothelial cell adhesion, meaning that the disease process may be able to bypass the regulatory pathways which would ordinarily moderate the inflammatory response.


Subject(s)
Blood Platelets/metabolism , Chemotaxis, Leukocyte/immunology , Leukocytes/immunology , Leukocytes/metabolism , Vascular Diseases/immunology , Vascular Diseases/metabolism , Animals , Atherosclerosis/drug therapy , Atherosclerosis/immunology , Atherosclerosis/metabolism , Cell Adhesion , Cell Aggregation , Cell Communication , Cell-Derived Microparticles/metabolism , Endothelial Cells/metabolism , Humans , Inflammation/immunology , Inflammation/metabolism , Leukocyte Rolling , Vascular Diseases/drug therapy
11.
Endocr Relat Cancer ; 19(4): 509-26, 2012 Aug.
Article in English | MEDLINE | ID: mdl-22673335

ABSTRACT

Protein arginine methyltransferase-6 (PRMT6) regulates steroid-dependent transcription and alternative splicing and is implicated in endocrine system development and function, cell death, cell cycle, gene expression and cancer. Despite its role in these processes, little is known about its function and cellular targets in breast cancer. To identify novel gene targets regulated by PRMT6 in breast cancer cells, we used a combination of small interfering RNA and exon-specific microarray profiling in vitro coupled to in vivo validation in normal breast and primary human breast tumours. This approach, which allows the examination of genome-wide changes in individual exon usage and total transcript levels, demonstrated that PRMT6 knockdown significantly affected i) the transcription of 159 genes and ii) alternate splicing of 449 genes. The PRMT6-dependent transcriptional and alternative splicing targets identified in vitro were validated in human breast tumours. Using the list of genes differentially expressed between normal and PRMT6 knockdown cells, we generated a PRMT6-dependent gene expression signature that provides an indication of PRMT6 dysfunction in breast cancer cells. Interrogation of several well-studied breast cancer microarray expression datasets with the PRMT6 gene expression signature demonstrated that PRMT6 dysfunction is associated with better overall relapse-free and distant metastasis-free survival in the oestrogen receptor (ER (ESR1)) breast cancer subgroup. These results suggest that dysregulation of PRMT6-dependent transcription and alternative splicing may be involved in breast cancer pathophysiology and the molecular consequences identifying a unique and informative biomarker profile.


Subject(s)
Alternative Splicing , Breast Neoplasms/diagnosis , Carcinoma/diagnosis , Gene Expression Regulation, Neoplastic , Nuclear Proteins/physiology , Protein-Arginine N-Methyltransferases/physiology , Alternative Splicing/genetics , Biomarkers, Tumor/analysis , Biomarkers, Tumor/genetics , Breast Neoplasms/genetics , Breast Neoplasms/metabolism , Carcinoma/genetics , Carcinoma/metabolism , Female , Gene Expression Profiling , Gene Expression Regulation, Enzymologic/drug effects , Gene Expression Regulation, Neoplastic/drug effects , Gene Expression Regulation, Neoplastic/genetics , Genetic Association Studies , Humans , Microarray Analysis , Nuclear Proteins/antagonists & inhibitors , Nuclear Proteins/genetics , Nuclear Proteins/metabolism , Prognosis , Protein-Arginine N-Methyltransferases/antagonists & inhibitors , Protein-Arginine N-Methyltransferases/genetics , Protein-Arginine N-Methyltransferases/metabolism , RNA, Small Interfering/pharmacology , Tumor Cells, Cultured , Validation Studies as Topic
12.
Nucleic Acids Res ; 38(7): 2201-16, 2010 Apr.
Article in English | MEDLINE | ID: mdl-20047962

ABSTRACT

It is well established that transcription and alternative splicing events are functionally coupled during gene expression. Here, we report that protein arginine N-methyltransferase 6 (PRMT6) may play a key role in this coupling process by functioning as a transcriptional coactivator that can also regulate alternative splicing. PRMT6 coactivates the progesterone, glucocorticoid and oestrogen receptors in luciferase reporter assays in a hormone-dependent manner. In addition, small interfering RNA (siRNA) oligonucleotide duplex knockdown of PRMT6 disrupts oestrogen-stimulated transcription of endogenous GREB1 and progesterone receptor in MCF-7 breast cancer cells, demonstrating the importance of PRMT6 in hormone-dependent transcription. In contrast, the regulation of alternative splicing by PRMT6 is hormone independent. siRNA knockdown of PRMT6 increases the exon inclusion:skipping ratio of alternatively spliced exons in endogenous vascular endothelial growth factor and spleen tyrosine kinase RNA transcripts in both the presence and absence of oestrogen. These results demonstrate that PRMT6 has a dual role in regulating gene expression and that these two functions can occur independently of each other.


Subject(s)
Alternative Splicing , Nuclear Proteins/metabolism , Protein-Arginine N-Methyltransferases/metabolism , Transcriptional Activation , Cell Line, Tumor , Cell Proliferation , Estradiol/pharmacology , Estrogen Receptor alpha/metabolism , Humans , Nuclear Proteins/antagonists & inhibitors , Nuclear Proteins/genetics , Nuclear Receptor Coactivator 1/metabolism , Protein-Arginine N-Methyltransferases/antagonists & inhibitors , Protein-Arginine N-Methyltransferases/genetics , Signal Transduction
13.
J Immunol ; 180(5): 3166-75, 2008 Mar 01.
Article in English | MEDLINE | ID: mdl-18292540

ABSTRACT

Dendritic cell (DC) differentiation is abnormal in type 1 diabetes mellitus (T1DM). However, the nature of the relationship between this abnormality and disease pathogenesis is unknown. We studied the LPS response in monocytes and monocyte-derived DCs isolated from T1DM patients and from non-T1DM controls. In T1DM patients, late LPS-mediated nuclear DNA binding by RelA, p50, c-Rel, and RelB was impaired as compared with type 2 DM, rheumatoid arthritis, and healthy subjects, associated with impaired DC CD40 and MHC class I induction but normal cytokine production. In TIDM monocytes, RelA and RelB were constitutively activated, and the src homology 2 domain-containing protein tyrosine phosphatase (SHP-1), a negative regulator of NF-kappaB, was overexpressed. Addition of sodium stibogluconate, a SHP-1 inhibitor, to DCs differentiating from monocyte precursors restored their capacity to respond to LPS in approximately 60% of patients. The monocyte and DC NF-kappaB response to LPS is thus a novel phenotypic and likely pathogenetic marker for human T1DM. SHP-1 is at least one NF-kappaB regulatory mechanism which might be induced as a result of abnormal inflammatory signaling responses in T1DM monocytes.


Subject(s)
Dendritic Cells/immunology , Dendritic Cells/pathology , Diabetes Mellitus, Type 1/immunology , Diabetes Mellitus, Type 1/metabolism , Monocytes/immunology , Monocytes/pathology , NF-kappa B/antagonists & inhibitors , NF-kappa B/physiology , Adolescent , Adult , Aged , Antigen Presentation/immunology , Cell Differentiation/immunology , Cells, Cultured , Child , Dendritic Cells/metabolism , Diabetes Mellitus, Type 1/pathology , Female , Humans , Lymphocyte Activation/immunology , MAP Kinase Signaling System/immunology , Male , Middle Aged , Monocytes/metabolism , NF-kappa B/metabolism , T-Lymphocyte Subsets/immunology , T-Lymphocyte Subsets/metabolism
14.
Nature ; 441(7089): 73-6, 2006 May 04.
Article in English | MEDLINE | ID: mdl-16672967

ABSTRACT

Since the mid-nineteenth century the Earth's surface has warmed, and models indicate that human activities have caused part of the warming by altering the radiative balance of the atmosphere. Simple theories suggest that global warming will reduce the strength of the mean tropical atmospheric circulation. An important aspect of this tropical circulation is a large-scale zonal (east-west) overturning of air across the equatorial Pacific Ocean--driven by convection to the west and subsidence to the east--known as the Walker circulation. Here we explore changes in tropical Pacific circulation since the mid-nineteenth century using observations and a suite of global climate model experiments. Observed Indo-Pacific sea level pressure reveals a weakening of the Walker circulation. The size of this trend is consistent with theoretical predictions, is accurately reproduced by climate model simulations and, within the climate models, is largely due to anthropogenic forcing. The climate model indicates that the weakened surface winds have altered the thermal structure and circulation of the tropical Pacific Ocean. These results support model projections of further weakening of tropical atmospheric circulation during the twenty-first century.


Subject(s)
Air Movements , Atmosphere/analysis , Greenhouse Effect , Human Activities , Tropical Climate , History, 19th Century , History, 20th Century , History, 21st Century , Models, Theoretical , Pacific Ocean , Seawater , Time Factors , Wind
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