Final answer:
The glacier sitting on land, once melted, would contribute more to the lake's water level rise since the iceberg floating in the lake is already displacing water. The glacier, once melted, will add its entire volume to the water level, unlike the iceberg, which has a neutral effect due to displacement rules.
Step-by-step explanation:
If both an iceberg floating in a lake and a glacier sitting on land next to the lake were to melt, the impact on the lake's water level would differ based on whether the ice is already in the water or on land. The melting iceberg that is already floating in the lake will not significantly change the water level due to the principle of displacement; it has already displaced its weight in water. In contrast, the glacier on land contains a volume of ice that is not already displacing the lake water. When it melts, it will add that volume to the lake, causing the water level to rise.
The increase in the water level is dependent on the volume of water released from the glacier. This is analogous to the situation described where if a large sheet of ice completely melts, the rise in water level is proportional to the volume of melted ice that was not previously displacing the water in the body. Thus, melting glaciers contribute to rising sea levels or in this case, lake levels.
Changes in the extent of sea ice and glaciers melting are indicators of climate change and have significant implications for ecosystems and human habitation. The effects include altering local ecosystems, biodiversity loss and potential displacement of people in coastal areas.