Why are Glacier’s glaciers shrinking? Determining whether a glacier is growing or receding involves a simple math equation. When more snow falls in the winter than melts in the summer, glaciers grow. When summer melting exceeds winter snowfall, they shrink. To determine how a glacier’s size (or mass balance) is changing, researchers measure the height of a glacier’s surface in late spring (accumulation peak) and late summer (melting peak). The late spring measurement shows how much snow accumula