Nearly every year in the late spring, ice blocks the flow of water at the mouth
of the Lena River in northeastern Russia and gives rise to floods across the
Siberian plains. This year’s floods can be seen in this image taken on June 2,
2002, by the MODIS (Moderate Resolution Imaging Spectroradiometer) instrument
aboard the Terra satellite. The river runs down the left side of the image, and
its delta is shrouded in ice (red) at the top of the image. Normally, the river would resemble a thin black line in MODIS imagery.
The river, which is Russia’s longest, flows 2,641 miles (4,250 kilometers) south
to north through Siberia and into the Laptev Sea. In the winter, the river
becomes nearly frozen. In the spring, however, water upstream thaws earlier
than water at the mouth of the river. As the southern end of the
river begins to melt, blocks of ice travel downstream to the still frozen delta,
pile up, and often obstruct the flow of water. Flooding doesn’t always occur on the same parts of the river. The floods hit further south last year. If the flooding grows severe enough, explosive charges
are typically used to break up the ice jams.
In these false-color images land areas are a dull, light green or tan, and water
is black. Clouds appear pink, and ice comes across as bright red.
In the span of three weeks, spring crept over the Siberian landscape surrounding the northern half of the Lena River. Many of the rivers in Earth’s temperate zones run high in the spring when melting snow and spring rain flood river basins. On the Lena River, however, spring flooding is almost inevitable for another reason: ice. Like other north-flowing rivers, the upper reaches of the Lena melt before their downstream counterparts. Because the northern mouth of the river remains frozen while the southern body of the river flows freely, water naturally builds behind the ice, forming a temporary reservoir that drains as the ice dwindles.