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As sea ice is floating in oceans, it is currently occupying a volume of oceans. And also ice is less dense than water, and thus it has a greater volume with the same amount of mass compared to water. So will melting sea ice directly cause a rise in the sea level?

Does melting sea ice have a direct influence in the rise of sea level or not? There may be indirect results which are out of scope of this question.

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    $\begingroup$ An answer in physics SE. $\endgroup$
    – user28185
    Commented Mar 4, 2023 at 8:04
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    $\begingroup$ Does this answer your question? Why doesn't sea level show seasonality? $\endgroup$
    – craq
    Commented Mar 6, 2023 at 1:49
  • $\begingroup$ Is the gist of the question whether 'the (literal) tip of the icebergs' is a significant effect or not? $\endgroup$ Commented Mar 6, 2023 at 9:53

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"Sea ices" - if referring to all kinds of ice floating in oceans - is not the same as "sea ice"; sea ice is specifically referring to seawater that has frozen and the total amount of water (and sea level) is not changed by it freezing or melting. So, no, it doesn't contribute to sea level rise from global warming.

Other kinds of ice floating in oceans include glacial ice that breaks off the terminus of glaciers and river ice that is carried by river flows into the oceans. As these get added to the oceans they add to sea levels.

This is glacial ice entering the oceans and adding it's volume to ocean volume -

glacial ice adding to sea levels

But it is important to understand that it is change to glacier mass balance that determines if that ice going into the oceans is causing sea level rise; if the snowfall in glacier catchments is less than ice and meltwater flow into oceans then it is adding to sea levels, but if glaciers get more snowfall than that it will result in sea level fall.

Currently global glacier mass balance is declining, with most glaciers in the world losing mass, ie glacier ice loss is currently adding to ocean volume and causing sea level rise.

Glacier mass balance

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With two exceptions, the answer is no. Sea ice forms from seawater. Sea ice forms from early autumn to early spring but then melts from early spring to early autumn. If there is any change in volume due to sea ice being nearly pure water while seawater is salty (note well: this is very small change), it repeats.

One exception is addition of ice and liquid water to the oceans from glaciers sliding into the ocean. Once that glacial ice detaches from the glacier it becomes sea ice. However, the sea level rise occurs when the glacial ice slides into the ocean and detaches from the ground, rather than later when that new sea ice melts.

The other exception is that water expands when it gets warmer. Less sea ice can form as the oceans get ever warmer. It is not however the freezing and melting of sea ice that make sea levels rise. That said, the reduced amounts of sea ice is one of many signs that the oceans are warming, and those warming ocean temperatures contribute to sea level rise.

Until the start of this century, thermal expansion and meltwaters appeared to be coequal in terms of causing sea level rise. Since then, meltwaters from glaciers and land-based ice sheets have been contributing considerably more to sea level rise than thermal expansion.

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The short answer is No.

If you want proof fill a glass to the brim with water. Place an ice cube in the water and wait for the ice to melt. Water will not overflow the glass.

The ice that is on land, as ice sheets on Greenland and Antarctica and in glaciers and in snow caps around the world is what will cause the ocean levels to rise as they melt, as the melt water from these will be adding water to the oceans.

Ice already floating on the oceans only returns to the oceans when it melts. The only reason why ice floats on water is because it is less dense than water.

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    $\begingroup$ fill a glass to the brim with water. / Place an ice cube in the water - this is the moment at which the glass will overflow, as you add new mass of water to the already-full glass. The volume it displaces (volume of the ice cube under water) = ice cube mass times the density of the liquid it's displacing. After cleaning up that spill, then you can do the experiment of waiting for it to melt. $\endgroup$ Commented Mar 6, 2023 at 3:34
  • $\begingroup$ Even after the initial spill, it will spill (not counting surface tension): Some of the ice is above the surface due to the 9% lower density ('tip of the ice berg'). Whether it is a significant effect wrt. planet sea level rise is another matter. $\endgroup$ Commented Mar 6, 2023 at 9:47
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    $\begingroup$ @PeterMortensen The important thing is not the volume of the ice, it's the volume of the water that the ice will turn into when it melts. This will be equal to the amount of water the ice displaces, so the ice above the surface does not count. $\endgroup$
    – Taemyr
    Commented Mar 6, 2023 at 10:47
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Actually, the total amount of water does not change; it is just in different forms...

The water on land came from rain which came from ocean evaporation, thus reducing the amount of water in the ocean.

With glacier melting that water comes back to the ocean temporary rising the ocean level.

At the same time as the global warming melts the glaciers, the same global warming also increase the evaporation of the ocean with rain falling on the land.

In the end, it is a balanced system.

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