Figure 1

Seasonal and interannual variation in SIP in a suite of temperate lakes. SIP is averaged over the top one m depth, and varies primarily as a function of differences in seasonally incident UV, water transparency to UV, and to a lesser extent elevation (Tahoe is 1,897 m above sea level, and Negra, 2,700 m). UV transparency varies within lakes as well (e.g. lower in nearshore bays and harbors than offshore in Tahoe, and because of long-term browning in more recent decades in Giles). Note the inverse seasonal patterns in the Northern Hemisphere vs. Southern Hemisphere. Lake latitude, name, and U.S. state or country are given.