As was mentioned earlier in the lab, the tropics are warmer than the poles because of differences in the angle at which solar radiation impacts the Earth (Figure 6.1). Very little solar radiation reaches higher latitude areas because the solar radiation comes in almost parallel to the Earth’s surface. Therefore, most of the thermal energy at higher latitudes comes from the movement of heat from the tropics. Heat is transported across the Earth’s surface through wind currents, storms, and ocean currents. In particular, large circular ocean currents, called gyres, appear to have a significant impact on the geographic distribution of heat on Earth and large-scale climate change in Earth’s history. These currents are particularly effective in melting polar ice in that they melt the sea ice from below. In addition, an examination of ocean current patterns will assist in explaining the patterns of sea ice extent you graphed earlier as the earth is warming (Part B and C).