Can Regulation of Freshwater Runoff in Hudson Bay Affect the Climate of the North Atlantic?

A sequence of phenomena links anthropogenic changes in the timing of freshwater runoff in Hudson Bay to a possible impact on the North Atlantic thermohaline circulation. The chain of events starts with the spreading of estuarine plumes under ice and continues with the effect of lowered salinity on the rate of ice formation, regional effects on the scale of Hudson Bay, the export of freshwater to the Labrador Sea, its impact on deep convection in that area, and the relative importance of such changes to the North Atlantic circulation. At each step we compare anthropogenic effects with other factors and place them within the perspective of natural variability. Our conclusion does not support the contention that freshwater runoff regulation, even of all rivers in the basins of Hudson and James Bays, could have a significant or even a detectable effect on the climate of the North Atlantic.Une séquence de phénomènes relie des changements anthropiques dans le moment où les eaux douces commencent à s'écouler dans la baie d'Hudson à leur répercussion possible sur les courants thermiques des eaux marines. La séquence débute par la formation d'un panache estuarien sous la glace et se poursuit avec l'effet de la baisse de salinité sur la vitesse de formation de la glace, des répercussions régionales affectant toute la baie d'Hudson, l'exportation d'eau douce vers la mer du Labrador et ses retombées sur la convection profonde dans cette zone, ainsi qu'avec l'importance relative de tels changements sur les courants nord-atlantiques. À chaque étape, on compare les influences anthropiques avec d'autres facteurs pour les situer dans un contexte de variabilité. Notre conclusion n'appuie pas la thèse que la régulation de l'écoulement des eaux douces, même si elle s'étendait à tous les cours d'eau des bassins de la baie d'Hudson et de la baie James, pourrait avoir des répercussions notables ou même détectables sur le climat nord-atlantique

The Arctic freshwater system : changes and impacts

Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 112 (2007): G04S54, doi:10.1029/2006JG000353.Dramatic changes have been observed in the Arctic over the last century. Many of these involve the storage and cycling of fresh water. On land, precipitation and river discharge, lake abundance and size, glacier area and volume, soil moisture, and a variety of permafrost characteristics have changed. In the ocean, sea ice thickness and areal coverage have decreased and water mass circulation patterns have shifted, changing freshwater pathways and sea ice cover dynamics. Precipitation onto the ocean surface has also changed. Such changes are expected to continue, and perhaps accelerate, in the coming century, enhanced by complex feedbacks between the oceanic, atmospheric, and terrestrial freshwater systems. Change to the arctic freshwater system heralds changes for our global physical and ecological environment as well as human activities in the Arctic. In this paper we review observed changes in the arctic freshwater system over the last century in terrestrial, atmospheric, and oceanic systems.The authors gratefully acknowledge the National Science Foundation (NSF) for funding this synthesis work. This paper is principally the work of authors funded under the NSF-funded Freshwater Integration (FWI) study

An investigation of thermal structure in two fresh-water lakes

The temperature fine structure of the thermocline in two stratified fresh water lakes is investigated using data from repeated vertical temperature profiles, and temperature time series from moored thermistor chains. The data show that much of the structure in the thermocline migrates through the water column with time. Analysis suggests that the migrating aspect of the structure is associated with the natural oscillations of the lake.A theory for the wind forced internal oscillations of a viscous, non-rotating, long-narrow lake of constant stratification is developed. The introduction of viscosity gives a smooth phase change with depth near the nodes of the vertical displacement profile, and enables the theory to model the observed vertical migration of features in the lake.The theory is compared to several aspects of the data from the two lakes. Phase profiles calculated from thermistor chain data are compared to the predicted phase profiles, and in the. diurnal frequency band where the wind forcing is strongest the agreement is good for values of the viscosity of about 0.1 cm2 sec 1. The amplitude of the vertical displacement, in the diurnal frequency band, agree best with values predicted by the theory for a viscosity of 0.2 cm2 sec 1, which, considering the errors involved, is not significantly different from the value obtained from the phase profiles. Comparisons are also made between the theory and observations of the energy as a function of the' forcing in various frequency bands, of the phase profiles as a function of frequency, and of the phase of the wind relative to the internal oscillations. The agreement in all cases is sufficient to warrant the description of the migrating structures in terms of damped internal oscillations of the lake.</p