system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When glaciers melt during the warmer months how much gets frozen back during the cooler months?

With all this exponential melting going on it got me thinking. What’s the net loss over time? How does cooler weather impact or regain any lost ice??
gpt
I think you misunderstand glaciers.  A glacier is a slow moving river of ice, flowing down a valley.  Glaciers don't directly regain "lost ice" that melted off at the end and flowed down to the ocean.

Glaciers flow out of fields of ice up in the mountains.  That's an area of high altitude, between mountain peaks, where many years of snowfall accumulate.  It never gets warm enough to melt all the snow that falls each year, so every year, more snow gets added than melted away.  As this snow builds up higher and higher, the weight of all that snow compresses the snow at the bottom into ice.

When an ice field like this overflows the edges - at points in between the mountain peaks, where there are lower passes - ice spills over the edge and starts flowing down a valley, very slowly.  Most of the time, there are multiple glaciers from one ice field, flowing in different directions.

How much a glacier advances or recedes each year is based on these factors:

* How quickly ice melts from the glacier - which happens mostly near the bottom, where it's lower altitude, and especially if the bottom of the glacier is directly touching a lake or ocean.

* How fast the glacier is flowing - which is based on things like how steep a slope it's flowing down.

* How much new ice is being fed to it from the ice field above.

Climate change can attack glaciers in these main ways:

1) Longer, warmer summers mean more of the glacier's ice melts each year.

2) Warmer air at high altitude can cause more snow up there to melt, slowing down the accumulation of new ice, or even causing more snow to melt than fell that year.  This can cause ice fields to shrink or even disappear, and completely stop feeding a glacier.

3) Changes in precipitation patterns can lead to more snow falling on the ice field each winter.  This especially happens because snow is more likely to fall at temperatures a little below freezing, than temperatures that are very far below freezing.  So in some places, as the climate warms, if more of the winter weather at the ice fields is a bit warmer bit still below freezing, this can cause *more* snow to accumulate each year.