When scientists talk about the cryosphere, they mean the places on Earth where water is in its solid form, frozen into ice or snow. Read more ...
On Friday, 17 October 2014 from 8:00 a.m. to 5:00 p.m. (USA Mountain Time), our Web site and FTP services will be unavailable because of system maintenance. We apologize for any inconvenience this may cause you.
(1) in mountainous regions, the line above which climatic conditions do not allow the upright growth of trees (2) the poleward limit of tree growth, also known as the tree line.