Environmental Education Outreach Program
PO Box 5768
Flagstaff, AZ 86011
Phone: 928-523-1275
Fax: 928-286-8882
Sand Dunes
Sand dunes & dune mobility
Sand dunes are typically classified by type: crescentic, linear, star, dome, and parabolic. With respect to dune mobility, however,
the general categories of interest are:
So what are the factors that influence dunes mobility?
The dune mobility index is an equation that incorporates the percent of time that wind speeds exceed transport threshold (W),
the annual precipitation (P), and finally, the annual evapotranspiration (PE).
M = W/(P/PE)
So then, how does climate change relate to dune mobility?
Climate model projections indicate that the desert Southwest will experience increased temperatures and decreased precipitation
in coming years. That means that we can anticipate a hotter and drier regional climate for the foreseeable future. Under the
projected climate conditions, precipitation (P) will continue to decrease, and the annual evapotranspiration (PE) will increase.
As this trend continues, the denominator will increase rendering a greater mobility index value (greater mobility).
But aren’t they just climate projections?
Global climate models, referred to as global circulation models (GCM), typically have resolutions of 200-300 km. Additional
detail and resolution can be achieved through the use of regional climate models (RCM) which cover much smaller areas on the
order of 25-50 km. These models are subject to rigorous review and produce highly reliable results. In addition, the different
GCM and RCM projections for the southwest provide consistent projections for decreased precipitation and increased temperatures.
The projections are highly reliable and furthermore, we are already feeling many of the projected effects of climate change
in the southwest.
How exactly do dunes migrate?
The U.S. Geological Survey, and in particular Dr. Margaret Hiza, have conducted a substantial amount of research on the subject
of dunes and dune migration. To learn more, please check out the link below. http://sgst.wr.usgs.gov/dunes/
The dust generated by dune erosion can be measured using a unique and inexpensive passive collection system. To learn
more, click HERE [pdf] .
Resources:
Lancaster, N. (1995). Geomorphology of Desert Dunes. New York, NY: Routledge.
For more information, please contact:
Mansel Nelson
928-523-1275 Mansel.Nelson@nau.edu
Inactive dune.
Partial active dune
Fully active dune.