20 results on '"Archer, Matthew"'
Search Results
2. Understanding Career Development Pathways of College Students With Disabilities Using Crip Theory and the Theory of Whole Self.
- Author
-
Chang-kyu Kwon, Guadalupe, Sarah S., Archer, Matthew, and Groomes, Darlene A.
- Abstract
Despite their growing numbers, college students with disabilities (SWD) are often overlooked in the context of campus support for career development. The purpose of this practice brief is to provide a framework and a set of recommended actions for higher education leaders, administrators, and staff in disability and career services in order to better support the unique needs of SWD in their career development. Through a combined lens of crip theory and the theory of whole self, we call for higher education institutions to (a) provide targeted career services for SWD, (b) build business partnerships through which SWD can develop careers, and (c) incorporate disability as a critical diversity factor of the institution for service effectiveness and sustainability. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
3. Frontal eddies provide an oceanographic triad for favorable larval fish habitat
- Author
-
Suthers, Iain M., Schaeffer, Amandine, Archer, Matthew, Roughan, Moninya, Griffin, David A., Chapman, Christopher C., Sloyan, Bernadette M., and Everett, Jason D.
- Abstract
Frontal eddies form on the shoreward edge of boundary currents, on average at weekly intervals and can last up to several weeks. This duration allows zooplankton production and completion of the larval stage of fish but may be too ephemeral for longer food chains with planktonic predators to establish. Therefore, frontal eddies may provide a suitable offshore nursery habitat, by entraining and retaining inner‐shelf water, preconditioned with coastal plankton and ichthyoplankton, into an upwelling favorable cyclonic eddy. Here, we briefly describe the behavior of frontal eddies formed by western boundary currents in the context of the fundamental ocean triad, which incorporates three processes for the successful reproduction of fish: nutrient enrichment, food concentration, and retention of larvae. We adapt this hypothesis for frontal eddies adjacent to the substantial fisheries production of continental shelves, creating conditions for enhanced recruitment potential of larval cohorts at a finer scale than previously considered. We review the evidence and investigations of frontal eddies in their capacity to entrain coastal water, sustain the plankton community through eddy uplift and retain distinctive coastal communities of larval fish offshore until larval development is complete. The process of frontal eddy formation is complex and such habitats are irregular yet ubiquitous, which present challenges and opportunities for their study. With the advance of ocean observing systems and integration of physical and biological sampling, frontal eddies provide a novel focus for understanding fisheries production and connectivity of coastal ecosystems.
- Published
- 2023
- Full Text
- View/download PDF
4. Sporadic Creutzfeldt-Jakob disease in Northern Tasmania
- Author
-
Rajalingam, Priyanka, de Souza, Aaron, Lee-Archer, Matthew, and Dhakal, Mahesh
- Abstract
Creutzfeldt-Jakob disease is a rare and incurable form of rapidly progressive neurodegenerative disease. The disease is fatal, and most patients die within 1 year of diagnosis. Clinical features include progressive cognitive dysfunction, delusions or hallucinations, cerebellar ataxia, myoclonus, visual disturbances, extrapyramidal signs and eventually akinetic mutism. Most patients present with varied clinical presentation, hence making it difficult to diagnose at an early stage. We report five cases of sporadic Creutzfeldt-Jakob disease presenting to a Tasmanian hospital in Australia over a period of 52 months. We highlight significant clinical features in all our patients including few atypical presentations, emphasise on relevant clinical biomarkers and illustrate characteristic abnormalities on electroencephalogram and neuroimaging.
- Published
- 2023
- Full Text
- View/download PDF
5. Conceptualizing the Marginalization Experiences of People with Disabilities in Organizations Using an Ableism Lens.
- Author
-
Kwon, Chang-kyu and Archer, Matthew
- Subjects
PEOPLE with disabilities ,ABLEISM ,WORK experience (Employment) ,CRITICAL analysis ,MINORITIES - Abstract
Existing literature on disability inclusion in the workplace has done little to confront the structural inequalities facing people with disabilities and has instead focused on ideas of assimilation strategies. As a result, in HRD there is a conflation between disability research and research that is "critical." The purpose of this conceptual article is to examine the persisting influence of ableism on the marginalization experiences of people with disabilities in organizations. Specifically, the present article conceptualizes the effects of ableism on the hiring, retention, and promotion of people with disabilities in organizations. The critical analysis of everyday work experiences of people with disabilities in ableist organizations as offered in this article calls for organizations to fundamentally rethink how they can better support this world's largest minority group. Implications for HRD research and practice will be discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
6. Sedation‐associated medications at dementia diagnosis, their receptor activity, and associations with adverse outcomes in a large clinical cohort.
- Author
-
Mbazira, Agnes, Bishara, Delia, Perera, Gayan, Rawlins, Elizabeth, Webb, Silas, Archer, Matthew, Balasundaram, Bharathi, Shetty, Hitesh, Tsamakis, Konstantinos, Taylor, David, Sauer, Justin, Stewart, Robert, and Mueller, Christoph
- Abstract
Background: We aimed to investigate whether sedative medications are associated with adverse outcomes in people with dementia, and whether specific characteristics of these medications predict a higher risk of harm. Method: A retrospective cohort study was carried out of 15,210 patients diagnosed with dementia between 2008 and 2017 in South London. From recorded medications at dementia diagnosis, we ascertained those with drowsiness listed as a side effect (termed 'sedative' hereafter) and subdivided them by frequency and strength of sedation, receptor profile, half‐life and whether they were psychotropics. Multivariable Cox regression models were applied to determine risk of mortality and emergency hospitalisation, and generalised estimating equations to investigate cognitive decline. Final models were adjusted for 19 potential confounders, including measures of physical and mental health, functioning and central anticholinergic burden. Result: At diagnosis 70.4% of patients with dementia were receiving at least one sedative medication. Median survival time was 4.0 years and median time to first hospitalisation 1.4 years. After controlling for potential confounders, receipt of any sedative medication at dementia diagnosis was associated with accelerated cognitive decline and a higher hospitalisation risk, but only medications with a cautionary warning yielded an increased mortality hazard. Medications acting through gamma‐aminobutyric acid agonism, psychotropic sedatives and those with a short half‐life were associated with a higher risk of mortality. Gamma‐aminobutyric acid agonists, N‐methyl‐D‐aspartate receptor antagonists and non‐psychotropic sedatives were associated with an increased hospitalisation risk. Alpha‐1 antagonist, antihistamines, N‐methyl‐D‐aspartate receptor antagonists, psychotropic sedatives, and those with shortest or longest half‐life were associated with accelerated cognitive decline. Conclusion: Receipt of any sedative agent was associated with hospitalisation and accelerated cognitive decline. Differences in hazard appear to exist between frequency/strength of sedation, receptor profiles, half‐life, and prescribing indication. These differences should be taken into consideration in medication reviews at the time of dementia diagnosis. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
7. How to govern a sustainable supply chain: Standards, standardizers, and the political ecology of (in)advertence
- Author
-
Archer, Matthew
- Abstract
There is an ambivalence within political ecology about whether the unequal power relations that emerge from many development projects are intended or unintended. This ambivalence is a result of an empirical focus on the effects of these programs on target communities, as opposed to an empirical focus on the people who are responsible for developing those programs. Drawing on qualitative fieldwork among people tasked with designing, promoting, and enforcing sustainability standards in global agricultural supply chains, I argue that the empowerment of multinational corporations and well-funded environmental NGOs that characterizes market-oriented sustainability programs is, in fact, intentional. This intention reflects the belief among sustainability professionals that the intersection of western scientific expertise with the dynamics of “the market” is the most effective way to promote sustainability in global supply chains, and to generate global sustainability in a more general sense. Concepts like “stakeholder engagement” and a commitment to flexibility and accommodation in the development and adoption of social and environmental standards are examples of what I call euphemistic sustainability, which shifts critical attention away from a balance of power that is increasingly tilted toward private interests, even as that imbalance remains an intended outcome of non-state market-driven governance systems like ostensibly voluntary sustainability standards.
- Published
- 2022
- Full Text
- View/download PDF
8. Imagining Impact in Global Supply Chains: Data-Driven Sustainability and the Production of Surveillable Space.
- Author
-
Archer, Matthew
- Subjects
SUPPLY chains ,METADATA ,DEVELOPING countries ,ECONOMIC impact ,RACE relations ,SUSTAINABILITY ,SPACE surveillance - Abstract
In the context of global agrocommodity supply chains, the sociotechnical imaginary of neoliberal sustainability is characterized by a belief that the impactfulness of market-based solutions like fair trade standards and voluntary certification schemes relies on the transparency and traceability of those supply chains. Achieving transparency and traceability, however, relies on the collection, analysis, and dissemination of data about numerous social, environmental, and economic factors, data that are generated through increasingly intensive regimes of high-tech monitoring and surveillance. For my interlocutors, who work to design and promote these standards, surveillance comes to be seen as not only justified but also expected and necessary, leading to the tacit categorization of certain spaces (and the human and non-human actors who populate them) as surveillable. In the case of sustainability standards specifically, which are imposed almost exclusively on producers in the Global South, the notion of surveillable space raises important questions about race and gender. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
9. Stakes and Stakeholders in the Climate Casino
- Author
-
Archer, Matthew
- Abstract
This essay advances a critique of the stakeholder concept based on the relative function of stakes and stakeholders in games of risk and reward such as roulette, cockfighting, and, if economists are right, climate negotiations. It asks what happens when corporate sustainability and other market-based “solutions” to socio-ecological crises such as climate change and mass extinction are perceived as a kind of casino. Dispossessed stakeholders become background props at sustainability conferences and other events where dramatic doom-and-gloom narratives of catastrophe serve as a way to reinforce global geographies of power and extraction. Being honest about the effects of categorizing such diverse actors as stakeholders or, alternatively, being clear about what exactly the word stakeholder means in terms of power and responsibility, is an important step in reaffirming the agency of the communities who stand to lose the most in the anthropocene.
- Published
- 2020
- Full Text
- View/download PDF
10. Extending thrombolysis to 4·5–9 h and wake-up stroke using perfusion imaging: a systematic review and meta-analysis of individual patient data
- Author
-
Campbell, Bruce C V, Ma, Henry, Ringleb, Peter A, Parsons, Mark W, Churilov, Leonid, Bendszus, Martin, Levi, Christopher R, Hsu, Chung, Kleinig, Timothy J, Fatar, Marc, Leys, Didier, Molina, Carlos, Wijeratne, Tissa, Curtze, Sami, Dewey, Helen M, Barber, P Alan, Butcher, Kenneth S, De Silva, Deidre A, Bladin, Christopher F, Yassi, Nawaf, Pfaff, Johannes A R, Sharma, Gagan, Bivard, Andrew, Desmond, Patricia M, Schwab, Stefan, Schellinger, Peter D, Yan, Bernard, Mitchell, Peter J, Serena, Joaquín, Toni, Danilo, Thijs, Vincent, Hacke, Werner, Davis, Stephen M, Donnan, Geoffrey A, Donnan, Geoffrey A., Davis, Stephen M., Ma, Henry, Campbell, Bruce C.V., Churilov, Leonid, Parsons, Mark W., Yan, Bernard, Mitchell, Peter J., Yassi, Nawaf, Sharma, Gagan, Desmond, Patricia M., Oxley, Thomas, Wu, Teddy Y., Shah, Darshan, Zhao, Henry, Rodrigues, Edrich, Salvaris, Patrick, Alemseged, Fana, Ng, Felix, Williams, Cameron, Ng, Jo-Lyn, Tu, Hans T-H., McDonald, Amy, Jackson, David, Tsoleridis, Jessica, McCoy, Rachael, Pesavento, Lauren, Weir, Louise, Bivard, Andrew, Kleinig, Timothy J., Patel, S., Harvey, J., Mahadevan, J., Cheong, E., Balabanski, Anna, Waters, Michael, Drew, Roy, Cranefield, Jennifer, Wijeratne, Tissa, Mackey, Elizabeth, Celestino, Sherisse, Low, Essie, Dewey, Helen M., Bladin, Christopher F., Loh, Poh Sien, Choi, Philip M., Coote, Skye, Frost, Tanya, Hogan, K., Ding, C., McModie, S., Zhang, W.W., Kyndt, Christopher, Moore, A., Ross, Z., Liu, J., Miteff, Ferdinand, Levi, Christopher R., Ang, Timothy, Spratt, Neil, Garcia-Esperon, Carlos, Kaauwai, Lara, Phan, Thanh G., Ly, John, Singhal, Shaloo, Clissold, Benjamin, Wong, Kitty, Krause, Martin, Day, Susan, Sturm, Jonathan, O'Brian, Bill, Grimley, Rohan, Thijs, Vincent, Simpson, Marion, Lee-Archer, Matthew, Brodtmann, Amy, Coulton, Bronwyn, Young, Dennis, Wong, Andrew A., Muller, Claire, Field, Deborah K., Vallat, W., Maxwell, Vanessa, Bailey, Peter, Sabet, Arman, Mishra, Sachin, Tan, Meng, George, K., Barber, P. Alan, Zhao, L., Meretoja, Atte, Curtze, Sami, Tatlisumak, Turgut, Sibolt, G., Tiainen, M., Koivu, M., Aarnio, K., Virta, J., Kasari, O., Eirola, S., Sun, M.C., Chen, T.C., Chuang, C.S., Chen, Y.Y., Lin, C.M., Ho, S.C., Hsiao, P.M., Tsai, C.H., Huang, W.S., Yang, Y.W., Huang, H.Y., Wang, W.C., Liu, C.H., Lu, M.K., Lu, C.H., Kung, W.L., Jiang, S.K., Wu, Y.H., Huang, S.C., Tseng, C.H., Tseng, L.T., Guo, Y.C., Lin, D., Hsu, C.T., Kuan, C.W., Hsu, J.P., Tsai, H.T., Suzuki, M., Sun, Y., Chen, H.F., Lu, C.J., Lin, C.H., Huang, C.C., Chu, H.J., Lee, C.Y., Chang, W.H., Lo, Y.C., Hsu, Y.T., Chen, C.H., Sung, P.S., Ysai, C.L., Jeng, J.S., Tang, S.C., Tsai, L.K., Yeh, S.J., Lee, Y.C., Wang, Y.T., Chung, T.C., Hu, C.J., Chan, L., Chiou, Y.W., Lien, L.M., Yeh, H.L., Yeh, J.H., Chen, W.H., Lau, C.L., Chang, A., Lee, I.Y., Huang, M.Y., Lee, J.T., Peng, G.S., Lim, J.C., Hsu, Y.D., Lin, C.C., Cheng, C.A., Yen, C.H., Yang, F.C., Hsu, C.H., Sung, Y.F., Tsai, C.K., Tsai, C.L., Hsiao, P.M., Lee, A., Hankey, Graeme, Blacker, David, Gerraty, Richard, Chen, C-I., Hsu, C-S., Cowley, Elise, McCoy, Rachael, Sallaberger, Michele, Snow, Barry, Kolbe, John, Stark, Richard, King, John, Macdonnell, Richard, Attia, John, D'Este, Catherine, Bernhardt, Julie, Carey, Leeanne, Cadilhac, Dominique, Anderson, Craig, Howells, David, Barber, A., Connelly, Alan, Macleod, Malcolm, O'Collins, Victoria, Wilson, W., Macaulay, L., Bendszus, Martin, Bluhmki, Erich, Eschenfelder, Christoph, Hacke, Werner, Molina, Carlos, Leys, Didier, Ringleb, Peter, Schellinger, Peter, Schwab, Stefan, Toni, Danilo, Wahlgren, Nils, Wardlaw, Joanna, Oppenheim, Catherine, Lees, Kennedy R., Kaste, Markku, von Kummer, Rüdiger, Chatellier, Gilles, Laage, Rico, Nuñez, Xavier, Ehrenkrona, Christina, Svenson, Ann-Sofie, Cove, Lynda, Niederkorn, Kurt, Gruber, Franz, Kapeller, Peter, Mikulik, Robert, Mas, Jean-Louis, Berrouschot, Jörg, Sobesky, Jan, Köhrmann, Martin, Steiner, Thorsten, Kessler, Christof, Fatar, Marc, Dziewas, Rainer, Poli, Sven, Althaus-Knaurer, Katharina, Bovi, Paolo, Rodriguez, Alain L., Arenillas, Juan F., Muir, Keith, Veltkamp, Roland, Dixit, Anand, Muddegowda, Girish, Kala, Lalit, De Silva, Deidre A., Butcher, Kenneth S., Byrnes, G., Peeters, Andre, Chalk, J.B., Fink, John N., Kimber, Thomas E., Schultz, David, Hand, Peter J., Frayne, Judith, Tress, Brian M., McNeil, John, Burns, R., Johnston, C., and Williams, M.
- Abstract
Stroke thrombolysis with alteplase is currently recommended 0–4·5 h after stroke onset. We aimed to determine whether perfusion imaging can identify patients with salvageable brain tissue with symptoms 4·5 h or more from stroke onset or with symptoms on waking who might benefit from thrombolysis.
- Published
- 2019
- Full Text
- View/download PDF
11. Regional immediate deep inferior epigastric perforator (DIEP) flap for immediate breast reconstruction: A collaborative multidisciplinary comparative audit in the information transfer in local versus regional referrals.
- Author
-
Osman, Elaf, Archer, Matthew, Mawhinney, Jamie, and Alder, Louise
- Subjects
MAMMAPLASTY ,KNOWLEDGE transfer - Published
- 2023
- Full Text
- View/download PDF
12. On the Variability of the East Australian Current: Jet Structure, Meandering, and Influence on Shelf Circulation
- Author
-
Archer, Matthew R., Roughan, Moninya, Keating, Shane R., and Schaeffer, Amandine
- Abstract
Given the importance of western boundary currents over a wide range of scales in the ocean, it is crucial that we understand their dynamics to accurately predict future changes. For this, we need detailed knowledge of their structure and variability. Here we investigate the jet structure of the East Australian Current (EAC), using observations from HF radars and moorings deployed at 30°S–31°S. Meandering, core velocity, width, and eddy kinetic energy (EKE) are quantified from 4 years of hourly 1.5 km resolution surface current maps (2012–2016), to obtain the most detailed representation of the surface EAC jet to date. The EAC flows predominantly over the ∼1,500 m isobath 50 km offshore but makes large amplitude displacements eastward every 65–100 days—the time scale associated with mesoscale eddy shedding at the EAC separation. Smaller‐amplitude, higher‐frequency meanders occur every 20–45 days. Using a coordinate frame that follows the jet, we show core velocity and EKE exhibit seasonality in both magnitude and variance, being maximum in summer (1.55 m s−1mean core velocity), minimum in winter (0.8 m s−1). However, it is the eddy‐shedding time scale that dominates jet variability. As the EAC moves shoreward, shelf temperature and along‐stream velocity vary linearly with jet movement, within ∼35 km of the core. The EAC is within this range 75% of the time, demonstrating its importance to the shelf circulation. Temperature and velocity fluctuations at the 70 m (100 m) isobath are more influenced by wind (EAC encroachment), with the strongest response occurring when wind and EAC act constructively. Meandering, core velocity, width, and eddy kinetic energy of the East Australian Current exhibit dominant variability at 65–100 daysAn annual cycle in the EAC core velocity and eddy kinetic energy has a maximum mean magnitude and variance in summer and minimum in winterOnshore movement of the EAC linearly increases shelf temperature and along‐stream velocity within a range of ∼35 km from its core
- Published
- 2017
- Full Text
- View/download PDF
13. The Surface Velocity Structure of the Florida Current in a Jet Coordinate Frame
- Author
-
Archer, Matthew R., Shay, Lynn K., and Johns, William E.
- Abstract
The structure and variability of the Florida Current between 25° and 26°N are investigated using HF radar ocean current measurements to provide the most detailed view of the surface jet to date. A 2‐D jet coordinate analysis is performed to define lateral displacements of the jet in time (meandering), and associated structural variations over a 2 year period (2005–2006). In the jet coordinate frame, core speed has a median value of ∼160 cm s−1at the central latitude of the array (25.4°N), with a standard deviation (STD) of 35 cm s−1. The jet meanders at timescales of 3–30 days, with a STD of 8 km, and a downstream phase speed of ∼80 km d−1. Meandering accounts for ∼45% of eddy kinetic energy computed in a fixed (geographical) reference frame. Core speed, width, and shear undergo the same dominant 3–30 day variability, plus an annual cycle that matches seasonality of alongshore wind stress. Jet transport at 25.4°N exhibits a different seasonality to volume transport at 27°N, most likely driven by input from the Northwest Providence Channel. Core speed correlates inversely with Miami sea level fluctuations such that a 40 cm s−1deceleration is associated with a ∼10 cm elevation in sea level, although there is no correlation of sea level to jet meandering or width. Such accurate quantification of the Florida Current's variability is critical to understand and forecast future changes in the climate system of the North Atlantic, as well as local impacts on coastal circulation and sea level variability along south Florida's coastline. The Florida Current surface jet exhibits dominant variability from 3 to 30 days in meandering, core speed, width, and shearThe jet structure undergoes a robust annual cycle in core speed, width, and shear, corresponding to local wind stressThe annual cycle of jet transport is very different between 25.5°N and 27°N, likely driven by input from the Northwest Providence Channel
- Published
- 2017
- Full Text
- View/download PDF
14. Exploring the mundane: Towards an ethnographic approach to bioenergy
- Author
-
Chatti, Deepti, Archer, Matthew, Lennon, Myles, and Dove, Michael R.
- Abstract
This article introduces the concept of ‘mundane bioenergy’, the largest source of renewable energy utilized by human society. While the term ‘renewable energy’ evokes images of solar panels and wind turbines, most renewable energy is used in a different form. This ‘mundane’ and largely invisible form of energy use takes place when families burn wood, dung, charcoal, and crop residue in cookstoves for their subsistence needs. We call on more energy ethnographers to grapple with mundane energy issues and strengthen this small but growing field of scholarship. Limited ethnographic scholarship on mundane energy issues leads to a partial understanding of emic perspectives and failed development initiatives. By sharing insights from our ongoing ethnographic research on mundane bioenergy, we demonstrate the value of bringing such insights into conversation with research in energy studies.
- Published
- 2017
- Full Text
- View/download PDF
15. Organic Sovereignties: Struggles over Farming in an Age of Free Trade. Guntra A.Aistara. Seattle, WA: University of Washington Press, 2018.
- Author
-
Archer, Matthew
- Published
- 2021
- Full Text
- View/download PDF
16. Abstract 10: Recurrent Ischemic Infarcts And Hemorrhages On MRI Within 30 Days Of Anticoagulation Commencement For Ischemic Stroke: Preliminary Results From The Attune Registry
- Author
-
Sharobeam, Angelos, Lam, Christina, Garcia-Esperon, Carlos, Krause, Martin, Wong, Andrew A, Lee, Andrew, Shah, Darshan, Lee-Archer, Matthew, Tan, Meng, Gawarikar, Yash, Gilligan, Amanda, Parsons, Mark, and Yan, Bernard
- Abstract
Introduction:Anticoagulation reduces recurrent ischemic stroke based on clinical definitions in patients with atrial fibrillation (AF). However, neuroimaging registries suggested a significant proportion developed ischemic lesions on magnetic resonance imaging (MRI) at 12 months follow up. The rate of early recurrent ischemic stroke identified by MRI remains unclear. ATTUNE (Atrial fibrillation in stroke - Utility of Neuroimaging Evaluation) is a prospective, multicentre study of clinical and radiological outcomes in patients commenced on anticoagulation after ischaemic stroke or TIA. We aimed to investigate the incidence of early ischemic stroke on MRI in this group of patients who were anticoagulated.Aims/Methods:We performed an interim analysis of the ATTUNE database to determine the proportion of patients with radiological evidence of infarction and haemorrhage on (MRI), one month after index ischemic stroke or transient ischemic attack (TIA). MRIs performed at one month were analysed independently by two experienced neuroimage assessors and the number of new infarcts and haemorrhages determined for each patient.Results:A total of 216 patients were analysed. The median age was 74 (IQR 68-81). Anticoagulation was commenced a median of 4 days after index event (IQR 2-6). Twenty-eight patients had new infarcts on follow-up MRI (13%). Fifty-six had new haemorrhage on follow up MRI (26%). Of these, 41 patients had hemorrhagic transformation of the initial infarct and 15 had a remote haemorrhage.Conclusion:There is a high rate of recurrent ischemic lesions and haemorrhages on MRI in patients commenced on anticoagulation within 30 days of index stroke or TIA.
- Published
- 2022
- Full Text
- View/download PDF
17. Reconstructing Fine‐Scale Ocean Variability via Data Assimilation of the SWOT Pre‐Launch In Situ Observing System
- Author
-
Archer, Matthew R., Li, Zhijin, Wang, Jinbo, and Fu, Lee‐Lueng
- Abstract
After the surface water and ocean topography (SWOT) satellite launches in 2022, an in‐situ field campaign will be conducted to estimate the ocean state for calibration and validation (CalVal) purposes. It is demonstrably difficult to capture the sea surface height (SSH) features that are the focus of SWOT, with short time periods (<20 days) and fine‐scale spatial structures (15–150 km). Therefore, a critical component of the SWOT CalVal will be a data assimilation (DA) system coupled to a primitive equation numerical model that can estimate: (a) the 2D SSH over the SWOT swaths, and (b) the 3D dynamical (velocity) field. To explore the ability of DA to meet the challenges of SWOT fine‐scale observations, a multiscale DA system based on an extended 3D variational method has been developed. Here, we present a strategic evaluation of this DA system, with a focus to assimilate in‐situ data from an observing system to best represent the fine‐scale ocean variability at the CalVal site. The DA estimate is compared to independent observations taken during the 2019 pre‐launch field campaign 300‐km off Monterey Bay, California. The key result is this DA system can reconstruct the upper 500‐m steric height with O(1‐cm) error at hourly resolution, and subcentimeter error for periods longer than 2 days. The surface water and ocean topography (SWOT) satellite mission is the first of its kind to launch. It will provide unprecedented measurements of the sea surface height in two dimensions (2‐D) and shorter spatial scales than previously possible. These measurements will allow oceanographers to study new scales of ocean variability and infer the ocean current velocity field. After SWOT launches, the accuracy of its measurements will need to be verified with observations made using standard instrumentation whose accuracy is well known. However, the cost to produce equivalent measurements for comparison with 2‐D high‐resolution SWOT observations is prohibitive, so the instruments to be deployed are only sufficient to evaluate a small portion of the satellite footprint. To better understand the satellite measurements, the plan is to combine the instrument measurements with a numerical ocean model that provides a four‐dimensional best‐estimate of the ocean state. This is called data assimilation (DA). In this paper, we evaluate a DA system developed to address these challenges, and show its successful performance using observations from a pre‐launch field campaign in 2019. Data assimilation (DA) of routine observations of large/mesoscale circulation allows effective assimilation of mooring data at fine scalesMooring DA reconstructs 0‐ to 500‐m hourly steric height with O(1‐cm) error, and subcentimeter error for periods longer than 2‐dayDA performance relies on observing system design; capturing the 2D horizontal gradient field is important for SWOT evaluation Data assimilation (DA) of routine observations of large/mesoscale circulation allows effective assimilation of mooring data at fine scales Mooring DA reconstructs 0‐ to 500‐m hourly steric height with O(1‐cm) error, and subcentimeter error for periods longer than 2‐day DA performance relies on observing system design; capturing the 2D horizontal gradient field is important for SWOT evaluation
- Published
- 2022
- Full Text
- View/download PDF
18. Increasing the Space–Time Resolution of Mapped Sea Surface Height From Altimetry
- Author
-
Archer, Matthew R., Li, Zhijin, and Fu, Lee‐Lueng
- Abstract
We present a mapping methodology to improve the resolution of gridded sea surface height (SSH) from multisatellite along‐track measurements, and apply it in the California Current system. This is motivated by the upcoming Surface Water and Ocean Topography (SWOT) satellite mission, which will collect novel high‐resolution wide‐swath SSH measurements. The calibration/validation of SWOT will be in the California Current and requires independent observations of SSH spatial variability. Our objective was to discover how far we could push the space–time resolution of SSH maps based on the existing altimetry constellation. Currently, the best SSH maps for the region are from AVISO's global product based on optimal interpolation (OI). Our methodology is based on 2‐D variational analysis (2DVAR), and we address some limitations of the AVISO OI global parameterization that restrict the resolution. Key improvements are (1) use of a background field incorporating mesoscale information, as opposed to a long‐term mean field; (2) optimized regional parameters; and (3) a representation error term in the observational error covariance matrix to account for the spread of measurements in time. Using a suite of independent remote and in situ observations, we show the 2DVAR method can produce higher‐resolution SSH maps in the California Current region that successfully capture smaller‐scale ocean features than AVISO, at the expense of an increase in noise. Satellite altimeters measure sea surface height (SSH) along one‐dimensional tracks across the ocean. Multiple tracks taken over a time window can be mapped onto a regularly spaced longitude‐latitude‐time grid to provide information of ocean variability that allows for a range of analyses. Here, we revisit the mapping process, motivated by the upcoming Surface Water and Ocean Topography (SWOT) satellite mission that will provide unprecedented high‐resolution measurements of SSH. SWOT will be calibrated/validated in the California Current, but currently, the best maps for comparison are from a global product not tailored to the region. While along‐track measurements resolve the SSH signal down to ~65 km, these maps only resolve scales > 200 km. Our goal was to increase map resolution by retaining more of the along‐track SSH signal. We developed a mapping methodology based on variational analysis. The new maps have higher variability at smaller scales, at the expense of an increase in noise. We show these maps compare better to independent data from in situ observing platforms, coastal radar, and satellite imagery of temperature and chlorophyll‐a. The ability to resolve shorter space–time scales of variability can have important implications for the study of ocean dynamics from altimetry. We develop a mapping methodology to grid multisatellite along‐track measurements of sea surface height in the California Current systemThis variational method prescribes regionally optimized parameters, an improved background field, and an observational representation errorThe new maps retain finer‐scale signals from the along‐track observations and compare well with a suite of independent observations
- Published
- 2020
- Full Text
- View/download PDF
19. Eddy‐Driven Cross‐Shelf Transport in the East Australian Current Separation Zone
- Author
-
Malan, Neil, Archer, Matthew, Roughan, Moninya, Cetina‐Heredia, Paulina, Hemming, Michael, Rocha, Carlos, Schaeffer, Amandine, Suthers, Iain, and Queiroz, Eduardo
- Abstract
In western boundary current systems, sharp velocity gradients between the poleward flowing jet and coastal waters generally act to inhibit cross‐shelf exchange. Downstream of jet separation, dynamic mesoscale eddies dominate the flow. In the East Australian Current System, counter‐rotating eddy dipoles are often present which, in the appropriate configuration, have potential to drive cross‐shelf transport. However, this eddy dipole mode is poorly understood in the framework of cross‐shelf exchange and the effect of these structures on shelf waters is uncertain. Using 25 years of satellite altimetry, as well as in situ sampling of a typical dipole event, we investigate the characteristics of eddy‐driven cross‐shelf exchange. We show that the maximum onshore velocity is driven by an eddy dipole structure and occurs in a defined latitudinal band between 33°S and 34°S more than 50% of the time. We sample a typical eddy dipole and find a strong onshore jet, 37 km wide, with velocities up to 1.78 m s −1and a transport of at least 16 Sv. Hydrographic data from an autonomous underwater glider show that this jet manifests on the shelf as a subsurface intrusion of warm salty water extending from offshore up onto the midshelf. In the light of climatic changes in western boundary current transport and the increase in their eddy kinetic energy, understanding eddy‐driven cross‐shelf exchange is important to predict future changes to the shelf water mass. An eddy dipole mode is the main driver of cross‐shelf transport in the East Australian Current extensionDipole events can result in onshore velocities up to 1.78 m s −1, with a maximum transport at 33–34°SWater from the observed dipole jet is advected from offshore up to the midshelf in the form of a warm salty intrusion of offshore water
- Published
- 2020
- Full Text
- View/download PDF
20. The MultICath study: creating an evidence base
- Author
-
Buckley, Brian, Archer, Matthew, Macaulay, Margaret, and Fader, Mandy
- Published
- 2015
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.