They say a picture says a thousand words. This week we published our 100th image in State of Flux, our gallery showing images of change around our planet. So hopefully by now you’re in awe of our home planet and the ways in which it is constantly changing, and aware of the impact us humans can have.
Each week for the past couple of years, we’ve published new images of different locations on planet Earth, showing change over time periods ranging from centuries to days. The pictures have been taken from space, by NASA’s Eyes on the Earth (its fleet of satellites whizzing above our heads), and from the ground, by real-life people. Some of the changes seen are related to, or exacerbated by, climate change, and some are not. Some document the effects of urbanization and man’s impact on the land, while others the ravage of disasters such as fires and floods.
Seeing our planet from space gives us a global view that we can’t get elsewhere. Through those eyes, we’ve witnessed damage caused by the recent tsunami in Japan, glacier melt in the Himalayas, the greening of China, the growth of Las Vegas and a century of global warming. We’ve looked at the march of deforestation in Bolivia, the rumblings of the (unpronounceable) Icelandic volcano Eyjafjallajökull, and the damming of the River Nile. Take a look below at some of our favorites. Sign up to our monthly newsletter or subscribe to our Facebook page if you want to keep up to date with our latest images. We’ll be launching a brand spanking new version of the gallery soon!
DELTA DEFENSE. Wax Lake Delta, Louisiana. Left: January 13, 1983. Right: January 2, 2011. The delta, where the Atchafalaya River flows into the Gulf of Mexico, was formed by sediment following the construction of a canal through Wax Lake in 1941. Since Hurricane Katrina in 2005, the delta has served as a model for restoring wildlife habitat and protection against storm surge in the Mississippi River delta region.
We recently read in the news that the earthquake and tsunami that struck Japan in March was strong enough to send waves that snapped a Manhattan-sized chunk of ice off the Sulzberger Ice Shelf some 8,100 miles away.
That’s true, but as pointed out at the end of this piece, there’s more to this story than just the strength of the earthquake. Though it’s not making it into the headlines, the condition of the ice in the region was also key. Specifically, the lack of nearby sea ice, coastal ice (also called fast or landfast ice) and pack ice made the portion of the Sulzberger Ice Shelf that broke off particularly susceptible to the incoming waves from the tsunami. Here’s how Kelly Brunt, the Goddard scientist who made the discovery, explained it in her Journal of Glaciology paper:
“The recent calving from the Sulzberger Ice Shelf suggests that, while the rifts provide the ice-shelf front with a zone that is weakened with respect to stress, and while tsunamis arrive episodically to cause vibrational disturbances to these rifts, some additional enabling condition must be satisfied before a given tsunami can lead to the detachment of an iceberg.
The timing of the earthquake and tsunami in Japan coincided with the typical summer sea-ice minimum (Zwally and others, 2002). As observed in the MODIS imagery and confirmed in the ASAR imagery, the region north of the Sulzberger Ice Shelf was devoid of either fast or pack ice at the time of predicted arrival of the tsunami. Fast ice is an important factor in ice shelf stability (Massom and others, 2010). Additionally, the absence of sea ice meant that the energy associated with the tsunami incident on the ice-shelf front was not damped by sea-ice flexure. With a distant tsunami source, over an irregular ocean bathymetry, and taking into account the dispersion of high-frequency components of the tsunami outside the shallow-water approximation, a complex pattern of dispersed waves is predicted in the wake of the leading front of the tsunami (NOAA/PMEL/Center for Tsunami Research; http://nctr.pmel.noaa.gov). As these waves interacted with the ice shelf over a period of hours to days, flexural modes may have been resonantly excited, each with the potential to trigger iceberg calving (Holdsworth and Glynn, 1978), in a pattern reminiscent of the delayed response of harbors documented in the far field during the 2004 Sumatra tsunami (Okal and others, 2006).
This study presents the first observational evidence linking a tsunami to ice-shelf calving. Specifically, the impact of the tsunami and its train of following dispersed waves on the Sulzberger Ice Shelf, in combination with the ice-shelf and sea ice conditions, provided the fracture mechanism needed to trigger the first calving event from the ice shelf in 46 years.”
Cross-posted from NASA's What on Earth blog. Adam is based in Washington, D.C.