title: Trends and abrupt changes in 104 years of ice cover and water temperature in a dimictic lake in response to air temperature, wind speed, and water clarity drivers

authors: Magee, Madeline R.

abstract: The one-dimensional hydrodynamic ice model, DYRESM-WQ-I, was modified to simulate ice cover and thermal structure of dimictic Lake Mendota, Wisconsin, USA, over a continuous 104-year period (1911-2014). The model results were then used to examine the drivers of changes in ice cover and water temperature, focusing on the responses to shifts in air temperature, wind speed, and water clarity at multiyear timescales. Observations of the drivers include a change in the trend of warming air temperatures from 0.081°C per decade before 1981 to 0.334°C per decade thereafter, as well as a shift in mean wind speed from 4.44ms-1 before 1994 to 3.74ms-1 thereafter. Observations show that Lake Mendota has experienced significant changes in ice cover: later ice-on date(9.0 days later per century), earlier ice-off date (12.3 days per century), decreasing ice cover duration (21.3 days per century), while model simulations indicate a change in maximum ice thickness (12.7cm decrease per century). Model simulations also show changes in the lake thermal regime of earlier stratification onset (12.3 days per century), later fall turnover (14.6 days per century), longer stratification duration (26.8 days per century), and decreasing summer hypolimnetic temperatures (-1.4°C per century). Correlation analysis of lake variables and driving variables revealed ice cover variables, stratification onset, epilimnetic temperature, and hypolimnetic temperature were most closely correlated with air temperature, whereas freeze-over water temperature, hypolimnetic heating, and fall turnover date were more closely correlated with wind speed. Each lake variable (i.e., ice-on and ice-off dates, ice cover duration, maximum ice thickness, freeze-over water temperature, stratification onset, fall turnover date, stratification duration, epilimnion temperature, hypolimnion temperature, and hypolimnetic heating) was averaged for the three periods (1911-1980, 1981-1993, and 1994-2014) delineated by abrupt changes in air temperature and wind speed. Average summer hypolimnetic temperature and fall turnover date exhibit significant differences between the third period and the first two periods. Changes in ice cover (ice-on and ice-off dates, ice cover duration, and maximum ice thickness) exhibit an abrupt change after 1994, which was related in part to the warm El Niño winter of 1997-1998. Under-ice water temperature, freeze-over water temperature, hypolimnetic temperature, fall turnover date, and stratification duration demonstrate a significant difference in the third period (1994-2014), when air temperature was warmest and wind speeds decreased rather abruptly. The trends in ice cover and water temperature demonstrate responses to both long-term and abrupt changes in meteorological conditions that can be complemented with numerical modeling to better understand how these variables will respond in a future climate.

text: Trends and abrupt changes in 104 years of ice cover and water temperature in a dimictic lake in response to air temperature, wind speed, and water clarity drivers The one-dimensional hydrodynamic ice model, DYRESM-WQ-I, was modified to simulate ice cover and thermal structure of dimictic Lake Mendota, Wisconsin, USA, over a continuous 104-year period (1911-2014). The model results were then used to examine the drivers of changes in ice cover and water temperature, focusing on the responses to shifts in air temperature, wind speed, and water clarity at multiyear timescales. Observations of the drivers include a change in the trend of warming air temperatures from 0.081°C per decade before 1981 to 0.334°C per decade thereafter, as well as a shift in mean wind speed from 4.44ms-1 before 1994 to 3.74ms-1 thereafter. Observations show that Lake Mendota has experienced significant changes in ice cover: later ice-on date(9.0 days later per century), earlier ice-off date (12.3 days per century), decreasing ice cover duration (21.3 days per century), while model simulations indicate a change in maximum ice thickness (12.7cm decrease per century). Model simulations also show changes in the lake thermal regime of earlier stratification onset (12.3 days per century), later fall turnover (14.6 days per century), longer stratification duration (26.8 days per century), and decreasing summer hypolimnetic temperatures (-1.4°C per century). Correlation analysis of lake variables and driving variables revealed ice cover variables, stratification onset, epilimnetic temperature, and hypolimnetic temperature were most closely correlated with air temperature, whereas freeze-over water temperature, hypolimnetic heating, and fall turnover date were more closely correlated with wind speed. Each lake variable (i.e., ice-on and ice-off dates, ice cover duration, maximum ice thickness, freeze-over water temperature, stratification onset, fall turnover date, stratification duration, epilimnion temperature, hypolimnion temperature, and hypolimnetic heating) was averaged for the three periods (1911-1980, 1981-1993, and 1994-2014) delineated by abrupt changes in air temperature and wind speed. Average summer hypolimnetic temperature and fall turnover date exhibit significant differences between the third period and the first two periods. Changes in ice cover (ice-on and ice-off dates, ice cover duration, and maximum ice thickness) exhibit an abrupt change after 1994, which was related in part to the warm El Niño winter of 1997-1998. Under-ice water temperature, freeze-over water temperature, hypolimnetic temperature, fall turnover date, and stratification duration demonstrate a significant difference in the third period (1994-2014), when air temperature was warmest and wind speeds decreased rather abruptly. The trends in ice cover and water temperature demonstrate responses to both long-term and abrupt changes in meteorological conditions that can be complemented with numerical modeling to better understand how these variables will respond in a future climate.

year: 2016

title: Over the threshold: learning and student retention in electronic courses

authors: Scott, Jonathan B.

subjects: electronics

abstract: Retention of students in early electronics courses is a problem acknowledged worldwide. It is a particular problem in universities, such as the University of Waikato, that have a common first-year programme because students can change streams (e.g. from electrical to mechanical) at the end of the first year. It is commonly believed that the major reason for the low level of student retention is practical engagement—mechanical engineers can see and get their hands on boats, cars, propellers, cogwheels and so forth from the start, while electronics is too small to see and handle, and its workings are alien to most school leavers.

text: Over the threshold: learning and student retention in electronic courses Retention of students in early electronics courses is a problem acknowledged worldwide. It is a particular problem in universities, such as the University of Waikato, that have a common first-year programme because students can change streams (e.g. from electrical to mechanical) at the end of the first year. It is commonly believed that the major reason for the low level of student retention is practical engagement—mechanical engineers can see and get their hands on boats, cars, propellers, cogwheels and so forth from the start, while electronics is too small to see and handle, and its workings are alien to most school leavers.

year: 2010-06

title: The Māori language curriculum for New Zealand schools: Spiral lesson/ lesson sequence design

authors: Johnson, Diane

subjects: Māori language teaching

abstract: A draft curriculum document for the teaching and learning of te reo Māori as a subject in mainstream schools in New Zealand (that is, in schools other than Kura Kaupapa Māori schools) was designed and trialled in 2004 and 2005. That draft is currently being reworked in line with the advice of those who trialled the document as well as that of a team of advisers set up by the Ministry of Education. The revised curriculum document will be submitted to the Ministry of Education in May 2006. As is the case with all new curriculum documents, the implementation phase will be critical. The extent to which this flexible, outcomes-focused curriculum document will genuinely inform new approaches to teaching and learning will depend not only upon the good will of teachers and communities, but also upon their ability to interpret the curriculum and to use it in a way that informs the design of language programmes, including the planning of units of work and of lessons and lesson sequences. In balancing language development and language practice, a communicative core and spiral approach is recommended, an approach in which there are core lessons (where the focus is language development) and spiral lessons (where the focus is language practice). In an earlier issue of this Journal (Johnson, 2003), one of us discussed core lesson design. Here, the design of spiral lessons is discussed and exemplified in the context of an outcomes-based curriculum.

text: The Māori language curriculum for New Zealand schools: Spiral lesson/ lesson sequence design A draft curriculum document for the teaching and learning of te reo Māori as a subject in mainstream schools in New Zealand (that is, in schools other than Kura Kaupapa Māori schools) was designed and trialled in 2004 and 2005. That draft is currently being reworked in line with the advice of those who trialled the document as well as that of a team of advisers set up by the Ministry of Education. The revised curriculum document will be submitted to the Ministry of Education in May 2006. As is the case with all new curriculum documents, the implementation phase will be critical. The extent to which this flexible, outcomes-focused curriculum document will genuinely inform new approaches to teaching and learning will depend not only upon the good will of teachers and communities, but also upon their ability to interpret the curriculum and to use it in a way that informs the design of language programmes, including the planning of units of work and of lessons and lesson sequences. In balancing language development and language practice, a communicative core and spiral approach is recommended, an approach in which there are core lessons (where the focus is language development) and spiral lessons (where the focus is language practice). In an earlier issue of this Journal (Johnson, 2003), one of us discussed core lesson design. Here, the design of spiral lessons is discussed and exemplified in the context of an outcomes-based curriculum.

year: 2005