Page 33 - living-ice

ILL.: REIBO
Carbon is the ocean’s
currency
We use carbon as a currency to understand how natural processes are interrelated. Carbon moves in a never-ending cycle between plants, animals, sea oor and atmosphere. During this cycle, carbon switches from alive to dead and from organic to inorganic – from the simplest form of carbon dioxide (CO2) to complex molecules in living organisms. Sinking carbon-rich materials link the upper and deep ocean together. Microscopic algae are an important component of the carbon cycle. The process by which carbon sinks and is transported from the ice and surface layer to the deep ocean using plants and animals is called the biological carbon pump. This pump contributes to removing CO2 from the atmosphere and storing it in the deep ocean or on the seabed. The biological carbon pump helps create a buffer against rising concentrations of CO2 in the atmosphere.
The sea ice affects this biological carbon pump in several ways. The algal production in and under the ice needs light and nutrients. The ice affects the amount of light that enters the ocean. Melting ice affects the supply of nutrients. When ice melts, a freshwater lens is formed that limits the supply of nutrient-rich deep water to the surface where algae have enough light to grow. Consequently, algal growth, CO2 uptake and nutrient absorption are limited by invisible boundaries created by melt- water from the sea ice.