reality, USGS

Discussion in 'Environment' started by Old Rocks, Feb 20, 2011.

  1. Old Rocks

    Old Rocks Diamond Member

    Oct 31, 2008
    Thanks Received:
    Trophy Points:
    Portland, Ore.

    • Since the mid-19th century, small glaciers (sometimes called “glaciers and ice caps;” see Box 2.1 for
    definitions) have been losing mass at an average rate equivalent to 0.3 to 0.4 millimeters per year of sea
    level rise.
    • The best estimate of the current (2007) mass balance of small glaciers is about –400 gigatons per year
    (Gt a–1), or nearly 1.1 millimeters sea level equivalent per year.
    • The mass balance loss of the Greenland Ice Sheet during the period with good observations increased
    from 100 Gt a–1 in the mid-1990s to more than 200 Gt a–1 for the most recent observations in 2006.
    Much of the loss is by increased summer melting as temperatures rise, but an increasing proportion is
    by enhanced ice discharge down accelerating glaciers.
    • The mass balance for Antarctica is a net loss of about 80 Gt a–1 in the mid-1990s, increasing to almost
    130 Gt a–1 in the mid-2000s. There is little surface melting in Antarctica, and the substantial ice losses
    from West Antarctica and the Antarctic Peninsula are very likely caused by increasing ice discharge as
    glacier velocities increase.
    • During the last interglacial period (~120 thousand years ago) with similar carbon dioxide levels to preindustrial
    values and arctic summer temperatures up to 4 °C warmer than today, sea level was 4–6 meters
    above present. The temperature increase during the Eamian was the result of orbital changes of the sun.
    During the last two deglaciations, sea level rise averaged 10–20 millimeters per year with large “meltwater
    fluxes” exceeding sea level rise of 50 millimeters per year lasting several centuries.
    • The potentially sensitive regions for rapid changes in ice volume are those with ice masses grounded
    below sea level such as the West Antarctic Ice Sheet, with 5 to 6 meters sea level equivalent, or large
    glaciers in Greenland like the Jakobshavn Isbræ, also known as Jakobshavn Glacier and Sermeq Kujalleq
    (in Greenlandic), with an over-deepened channel (channel below sea level, see Figure 2.10) reaching far
    inland; total breakup of Jakobshavn Isbræ ice tongue in Greenland, as well as other tidewater glaciers
    and ice cap outlets, was preceded by its very rapid thinning.
  2. Mini 14

    Mini 14 Senior Member

    Jun 6, 2010
    Thanks Received:
    Trophy Points:

Share This Page