The SOLAS air-sea gas exchange experiment (SAGE) 2004

Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 58 (2011): 753-763, doi:10.1016/j.dsr2.2010.10.015.The SOLAS air-sea gas exchange experiment (SAGE) was a multiple-objective study investigating gas-transfer processes and the influence of iron fertilisation on biologically driven gas exchange in high-nitrate low-silicic acid low-chlorophyll (HNLSiLC) Sub-Antarctic waters characteristic of the expansive Subpolar Zone of the southern oceans. This paper provides a general introduction and summary of the main experimental findings. The release site was selected from a pre-voyage desktop study of environmental parameters to be in the south-west Bounty Trough (46.5°S 172.5°E) to the south-east of New Zealand and the experiment conducted between mid-March and mid-April 2004. In common with other mesoscale iron addition experiments (FeAX’s), SAGE was designed as a Lagrangian study quantifying key biological and physical drivers influencing the air-sea gas exchange processes of CO2, DMS and other biogenic gases associated with an iron-induced phytoplankton bloom. A dual tracer SF6/3He release enabled quantification of both the lateral evolution of a labelled volume (patch) of ocean and the air-sea tracer exchange at the 10’s of km’s scale, in conjunction with the iron fertilisation. Estimates from the dual-tracer experiment found a quadratic dependency of the gas exchange coefficient on windspeed that is widely applicable and describes air-sea gas exchange in strong wind regimes. Within the patch, local and micrometeorological gas exchange process studies (100 m scale) and physical variables such as near-surface turbulence, temperature microstructure at the interface, wave properties, and wind speed were quantified to further assist the development of gas exchange models for high-wind environments. There was a significant increase in the photosynthetic competence (Fv/Fm) of resident phytoplankton within the first day following iron addition, but in contrast to other FeAX’s, rates of net primary production and column-integrated chlorophyll a concentrations had only doubled relative to the unfertilised surrounding waters by the end of the experiment. After 15 days and four iron additions totalling 1.1 tonne Fe2+, this was a very modest response compared to the other mesoscale iron enrichment experiments. An investigation of the factors limiting bloom development considered co- limitation by light and other nutrients, the phytoplankton seed-stock and grazing regulation. Whilst incident light levels and the initial Si:N ratio were the lowest recorded in all FeAX’s to date, there was only a small seed-stock of diatoms (less than 1% of biomass) and the main response to iron addition was by the picophytoplankton. A high rate of dilution of the fertilised patch relative to phytoplankton growth rate, the greater than expected depth of the surface mixed layer and microzooplankton grazing were all considered as factors that prevented significant biomass accumulation. In line with the limited response, the enhanced biological draw-down of pCO2 was small and masked by a general increase in pCO2 due to mixing with higher pCO2 waters. The DMS precursor DMSP was kept in check through grazing activity and in contrast to most FeAX’s dissolved dimethylsulfide (DMS) concentration declined through the experiment. SAGE is an important low-end member in the range of responses to iron addition in FeAX’s. In the context of iron fertilisation as a geoengineering tool for atmospheric CO2 removal, SAGE has clearly demonstrated that a significant proportion of the low iron ocean may not produce a phytoplankton bloom in response to iron addition.SAGE was jointly funded through the New Zealand Foundation for Research, Science and Technology (FRST) programs (C01X0204) "Drivers and Mitigation of Global Change" and (C01X0223) "Ocean Ecosystems: Their Contribution to NZ Marine Productivity." Funding was also provided for specific collaborations by the US National Science Foundation from grants OCE-0326814 (Ward), OCE-0327779 (Ho), and OCE 0327188 OCE-0326814 (Minnett) and the UK Natural Environment Research Council NER/B/S/2003/00282 (Archer). The New Zealand International Science and Technology (ISAT) linkages fund provided additional funding (Archer and Ziolkowski), and the many collaborator institutions also provided valuable support

Motivating Students by “Personalizing” Learning Around Individual Interests: A Consideration of Theory, Design and Implementation Issues

Purpose As educators seek ways to enhance student motivation and improve achievement, promising advances are being made in adaptive approaches to instruction. Learning technologies are emerging that promote a high level of personalization of the learning experience. One type of personalization is context personalization, in which instruction is presented in the context of learners’ individual interests in areas like sports, music, and video games. Personalized contexts may elicit situational interest, which can in turn spur motivational and metacognitive states like positive affect and focused attention. Personalized contexts may also allow for concepts to become grounded in prior knowledge by fostering connections to everyday activity. In this Chapter, we discuss the theoretical, design, and implementation issues to consider when creating interventions that utilize context personalization to enhance motivation

Building cohesion across representations: A mechanism for STEM integration

Abstract Purpose The mechanisms of integration of science, technology, engineering, and mathematics (STEM) remain largely underspecified in the research and policy literatures, despite their purported benefits. Our novel claim is that one key mechanism of STEM integration is producing and maintaining cohesion of central concepts across the range of representations, objects, activities, and social structures in the engineering classroom. Method We analyze multiviewpoint videos of multiday classroom activities from Project Lead the Way (PLTW) classes in digital electronics in two urban high schools. Results To forge cohesion, teachers use coordination of representations, tools, and materials, and they use projection to reference places and events, past and future. Teachers also perform explicit identification to label central invariant relations that are the conceptual focus of their instruction. Teachers typically perform identification, coordination, and projection on the particular STEM representations used in projects in order to improve the cohesion of the conceptual content of a curriculum unit. Teachers can also represent the larger sequence of project activities within the curriculum to construct a cohesive account of how the various activities and representations relate and build upon key ideas. Conclusions This paper found that cohesion-producing activities promote student understanding by threading conceptual relations through different mathematical representations, scientific laws, technological objects, engineering designs, learning spaces, and social structures. In these ways, cohesion can promote STEM integration in the engineering classroom

Posing mathematics problems about STEM careers: problem quality, scaffolds, and problem solving

Mathematical problem posing, or authoring mathematical tasks, can allow students to integrate their interests and experiences into the classroom. Little research has explored different designs for scaffolding or facets of posed problem quality, particularly when problem posing is based on students’ interests. We created an environment that enabled 39 community college students to author algebra problems related to their career interests, and explore four problem-posing scaffolds – video, vignette, example problem, and template. We use a design-based research approach to examine affordances of career problem-posing. Engaging in problem-posing was associated with increased interest in learning mathematics. Use and time spent with scaffolds and time-on-task were related to quality of posed problems, and problem quality features were related to students’ ability to solve problems they posed. Text analyses revealed scaffold use was associated with the language students used in the problems they posed. Implications for problem posing in mathematics classrooms are discussed.</p

Physical and dynamical oceanography of Liverpool Bay

The UK National Oceanography Centre has maintained an observatory in Liverpool Bay since August 2002. Over 8 years of observational measurements are used in conjunction with regional ocean modelling data to describe the physical and dynamical oceanography of Liverpool Bay and to validate the regional model, POLCOMS. Tidal dynamics and plume buoyancy govern the fate of the fresh water as it enters the sea, as well as the fate of its sediment, contaminants and nutrient loads. In this context, an overview and summary of Liverpool Bay tidal dynamics are presented. Freshwater forcing statistics are presented showing that on average the bay receives 233 m3 s - 1. Though the region is salinity controlled, river input temperature is shown to significantly modulate the plume buoyancy with a seasonal cycle. Stratification strongly influences the region's dynamics. Data from long-term moored instrumentation are used to analyse the stratification statistics that are representative of the region. It is shown that for 65% of tidal cycles, the region alternates between being vertically mixed and stratified. Plume dynamics are diagnosed from the model and are presented for the region. The spring-neap modulation of the plume's westward extent, between 3.5 ° W and 4° W, is highlighted. The rapid eastward erosion of the plume during spring tides is identified as a potentially important freshwater mixing mechanism. Novel climatological maps of temperature, salinity and density from the CTD surveys are presented and used to validate numerical simulations. The model is found to be sensitive to the freshwater forcing rates, temperature and salinities. The existing CTD survey grid is shown to not extend sufficiently near the coast to capture the near coastal and vertically mixed component the plume. Instead the survey grid captures the westward spreading, shallow and transient, portion of the plume. This transient plume feature is shown in both the long-term averaged model and observational data as a band of stratified fluid stretching between the mouth of the Mersey towards the Isle of Man. Finally the residual circulation is discussed. Long-term moored ADCP data are favourably compared with model data, showing the general northward flow of surface water and southward trajectory of bottom wate