The Interaction of Large Amplitude Internal Seiches with a Shallow Sloping Lakebed: Observations of Benthic Turbulence in Lake Simcoe, Ontario, Canada

نویسندگان

  • Remo Cossu
  • Mathew G. Wells
چکیده

Observations of the interactions of large amplitude internal seiches with the sloping boundary of Lake Simcoe, Canada show a pronounced asymmetry between up- and downwelling. Data were obtained during a 42-day period in late summer with an ADCP and an array of four thermistor chains located in a 5 km line at the depths where the thermocline intersects the shallow slope of the lakebed. The thermocline is located at depths of 12-14 m during the strongly stratified period of late summer. During periods of strong westerly winds the thermocline is deflected as much as 8 m vertically and interacts directly with the lakebed at depth between 14-18 m. When the thermocline was rising at the boundary, the stratification resembles a turbulent bore that propagates up the sloping lakebed with a speed of 0.05-0.15 m s(-1) and a Froude number close to unity. There were strong temperature overturns associated with the abrupt changes in temperature across the bore. Based on the size of overturns in the near bed stratification, we show that the inferred turbulent diffusivity varies by up to two orders of magnitude between up- and downwellings. When the thermocline was rising, estimates of turbulent diffusivity were high with KZ ∼10(-4) m(2)s(-1), whereas during downwelling events the near-bed stratification was greatly increased and the turbulence was reduced. This asymmetry is consistent with previous field observations and underlines the importance of shear-induced convection in benthic bottom boundary layers of stratified lakes.

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Impacts of hydrodynamics and benthic communities on phytoplankton distributions in a large, dreissenid-colonized lake (Lake Simcoe, Ontario, Canada)

We quantified the vertical and horizontal variation of chlorophyll a (Chl-a) to test how benthic filter feeders (dreissenid mussels), rooted macrophytes, and hydrodynamics influence phytoplankton distributions in a large lake (Lake Simcoe, Canada). Water column Chl-a did not differ significantly among sites of different depth, distance offshore, or rooted macrophyte biomass, but among the nears...

متن کامل

A Simple Method to Improve Hazelnut Grafting

Hazelnuts are usually propagated by suckers or layering. However, other methods of propagation have been tested with variable results. Grafting is a method that has a few advantages such as fast multiplication rate, earlier fruiting and reducing sucker removal cost on specific rootstocks. Unfortunately, grafting is difficult due to slow formation of callus in hazelnuts. Here, we report the hypo...

متن کامل

Tests of an extension to internal seiches of Defant’s procedure for determination of surface seiche characteristics in real lakes’

The success of A. Defant’s method of calculating surface seiche periods and structures in real lakes is well known. To test whether it can bc adapted and applied with similar success in studies of internal seiches in stratified lakes, in which density structure is simulated by two homogeneous layers, we compare the predictions of a computerized version of Mortimer’s modified Defant procedure ag...

متن کامل

Modelling phosphorus dynamics in multi-branch river systems: a study of the Black River, Lake Simcoe, Ontario, Canada.

High rates of nutrient loading from agricultural and urban development have resulted in surface water eutrophication and groundwater contamination in regions of Ontario. In Lake Simcoe (Ontario, Canada), anthropogenic nutrient contributions have contributed to increased algal growth, low hypolimnetic oxygen concentrations, and impaired fish reproduction. An ambitious programme has been initiate...

متن کامل

Experiments on Internal Wave Resonance in Periodically Forced Lakes

Laboratory experiments were conducted to determine the steady state internal wave response of a periodically forced long and narrow lake. The system is two-layer stratified and is subjected to periodic forcing over a wide frequency range. The ratio of the forcing frequency (f) to horizontal mode-one (H1) internal seiche frequency (fH1) governs the system response. For f ≥ 2fH1, highermode inter...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:

دوره 8  شماره 

صفحات  -

تاریخ انتشار 2013