Final answer:
The temperature-versus-depth profile of inland lakes differs from oceans because deeper lake water can be warmer during winter due to water's maximum density at around 4°C, and due to summer stratification and fall turnover that mixes nutrients and oxygen throughout the lake.
Step-by-step explanation:
The temperature-versus-depth profiles of the Great Lakes or Wisconsin's inland lakes differ from those in the oceans primarily due to thermal stratification and turnover events caused by water density variations with temperature changes. In winter, there is warmer water at depth in these lakes because water is densest and has maximum density at around 4°C, which is why the deeper water, which is warmer than the ice-covered surface, is found at this temperature. This contrasts with ocean profiles, where temperature generally decreases with depth. In summer, lakes experience stratification, with warmer water at the surface and cooler water below, until fall turnover occurs, allowing for the mixing of oxygen and nutrients throughout the lake.
During the fall turnover, the top layers cool to 4°C and sink, displacing the warmer bottom water and allowing nutrient cycling and oxygen replenishment. Conversely, tropical lakes may have less pronounced turnovers due to a smaller variation in seasonal temperature changes. Finally, due to specific heat properties, lakes undergo smaller temperature changes than air, contributing to stability in the temperature-versus-depth profile over short time spans.