Fresh-water polar ice caps melting into salt-water oceans alter the ocean gulf-stream patterns that regulate temperatures. This process leads to major temperature-pattern changes around Earth.
The changing landscapes and higher temperatures in polar regions will endanger countless animal and plant species, and irretreivably alter the balance of the ecosystem.
Ice caps and glaciers serve as sunlight reflectors, bouncing high-temperature sun rays back into space and away from Earth. When these natural structures have diminished greatly or vanished, Earth will be further warmed as the darker oceans absorb much of the sun ray heat.