Landsat 9 photographs three boreal rivers pouring tea-brown water into James Bay

On September 27, Landsat 9 recorded the color of the river water ^[1]. Colored dissolved organic matter, or CDOM, absorbs light in the blue and ultraviolet parts of the spectrum, so water carrying a lot of it looks brown ^[3]. The compounds include substances derived from tannins and lignins, which leach out of decaying leaves, roots, bark and soil, much as similar substances stain tea ^[4]. Here the supply is the boreal forest and boggy wetland the rivers cross in northern Quebec and Ontario before reaching Hannah and Rupert bays, the southernmost arms of James Bay ^[2].

There is a second brown in the scene. Tides and river currents stir up the mudflats and lift lighter brown plumes of suspended sediment that mix with the incoming river water ^[6]. Those plumes are particles of mud. Dissolved organic matter and suspended sediment both push the water toward brown, and in this image they meet at the river mouths ^[1][6]. The flats exist because the floor of southern James Bay is shallow and gently sloping, postglacial rebound is slowly lifting the land, and the rivers keep depositing fine mud ^[5].

NASA's account explains where the tea-colored water goes and why it has that color, but it does not report CDOM concentrations, river discharge or an estimate of the carbon delivered to the bay ^[13]. A flux needs both quantities: how much organic matter is in the water, and how much water passes. One frame from one day supplies neither, though it does show where boreal river water spread across the flats that day ^[1].

Onshore, NASA hedges too. It says differences in moisture and vegetation "likely" produce the green, veinlike branching: denser forest along stream channels shows dark green, while poorly drained peat bog with less tree cover shows lighter green ^[7].

The shade has a Cree name. Pahtaaunaakun means "color of singed beaver" in Southern East Cree ^[8]. European traders came to Rupert Bay for beaver as early as the 1660s. Their trade led to several posts on the bay's shores and to the founding of the Hudson's Bay Company ^[9]. In the 1830s, and again about a century later, in roughly the 1930s, the company and local Cree set up Charlton Island as a place to raise beavers for trapping ^[10][14]. Once predators were removed and breeding pairs delivered, the island's beaver population ballooned, according to historical accounts ^[10]. A Cree myth recorded by the anthropologist Alanson Skinner says Stag Rock, the island at the Nottaway's mouth, is a rock a giant hurled at a fleeing giant beaver, and missed ^[11].

The images are by Lauren Dauphin of NASA Earth Observatory, made with Landsat data from the U.S. Geological Survey; the story is by Adam Voiland ^[12].