The Nile Delta

The MERIS instrument flown onboard Envisat is particularly adapted to highlighting visible processes such as sediment input from rivers and the distribution of river sediment by marine coastal processes.









A single acquisition over the Nile Delta made using the MERIS instrument reveals the striking contrast between the pale sands of the Sahara and the bright green of the course of the Nile and its delta, in the simulated true-colour image at left.

At right, bands 15, 13, and 2 have been used to bring out the extent of the Nile plume as sediment is carried from the river into the Eastern Mediterranean. Band 2 highlights surface sediment; bands 15 and 13, in the near-infrared, highlight the difference over land.

Once a seasonal phenomenon, the Nile flood, up to 1965 when the Aswan High Dam became fully operational, provided massive amounts of silt to the delta and the Eastern mediterranean, renewing soil fertility and providing nutrients on which shrimp and phytoplankton populations, thus fisheries, thrived. Today the sediment plume, negligeable when compared with the approximately 100 million metric tonnes of sediment retained behind the Aswan High Dam, is present year-round. It issues both from the Nile and from the Suez, as is clear in the MERIS image at right above.


see the following gallery and search for Nile Delta

Nile Delta photos from satellite


Another image shows that by enhancing a particular part of the data it is possible to render visible the processes which transport Nile and Red Sea sediment along the coast. Here, data in band 7 has been further stretched to show the sedimentation processes along the coast. Representing perhaps finer sediment, a visible blue plume farther north, which can also be seen in the 15, 13, 2 image, is probably a result of sediment being carried out by the river itself.

These images of the Nile Delta were acquired on March 1st, 2003.

A full description of the capabilities of the MERIS instrument can be found in the MERIS Product Handbook. Other images from ENVISAT's first year in orbit are available in the Envisat Image Gallery.

Freedom from noise

There is a great deal of talk on freedom of speech. I submit that there is another freedom, too - the freedom from noise. I mean one should be free from what one doesn't want to hear, like spam. This is why I have turned on the moderation on the comments here. So I can filter out the spam, the noise.

Sorry, those who made noise. Others, who made constructive comments, have had their comments published.

Glaciers melting in Himalayas

Revenge of the 'Wild Roses'

By Arshad H Abbasi

The present debate is not over the war or ceasefire on the longest glacier known as 'Wild Roses" in the local language but on the concern over the melting of the Siachen Glacier , Known as the world's longest glacier in the non-polar regions, its melting process has now been bracketed amongst the fastest in the world. Its retreat is evident from the snout (base of the glacier) and through the continuous thinning of ice along its entire length.

The Siachen, along with several other major tributary glaciers, reduced its volume by 35 per cent during the last twenty years, retreating at the rate of 110 meter per year. Hydrological analyses too are substantiating this glacier melt. A study on temperature trends of high altitude stations in this region shows temperature is increasing at the rate of 0.20 degrees centigrade annually. The extraordinary melting of Siachen and other major tributary glaciers is caused by human activity, and is not due to natural changes. It has not only led to formations of glacial lakes and snow hole, but is responsible for destructive snow avalanches on both side of Saltoro ridge.

The problem is being caused by the establishment of permanent cantonments on either side of the Saltoro ridge, the daily heavy air traffic to advance camps (up to Indra Col post), the cutting and melting of glacial ice through the application of chemical, daily dumping of more than a ton of chemicals, metals, organic and human waste, daily leakages from 2000 gallons of kerosene oil from 250 km plastic pipeline laid by India throughout the glacier. The unprecedented increase in the flow of the Nubra River, emerging from the Siachen Glaciers further supports the melting process. More so, as the yearly swelling of this river is now destroying carefully constructed bridges and infrastructure along its course. Would this be ' Siachen's Revenge" against the massive human intervention into its natural ecology?

Two decades of military activities, with daily jet flights carrying men and material into the world's highest military airport 'Thoise", at the foot of the Siachen, hourly helicopter flights, facilitated by "Sonam" helipad on the glacier at 21000 ft, provide service to the highest camp site at Base Indra. At this height, the fuel efficiency and load-carrying capacity of a helicopter is reduced to 30 per cent. Its proficiency in disturbing freshly accumulate snow is undoubtedly outstanding, while simultaneously contributing to thinning the ice. Surely clear evidence of human-influenced warming the world's largest glacier, which will have serious long-term repercussion on the water resources with climatic changes at regional and global level.

Joined in this process of rapid ice melting, is the mountain-engineering feat completed in 1986, which laid an all weather road, purely as support-line to the military activities in the Siachen. With its final destination the Nubra Valley, routed from Delhi-Manali-Leh, it requires crossing the highest passes in the world, including the 5.300 meters high Tanglang La Pass.

A death sentence seems to be hanging over this region. The constant movement of heavy military vehicles, which in turn are dependent on ancillary support along its way, are further endangering the ecology of the known 6500 glaciers in this Himalayan regions, particularly Kashmir, Himachal Pradesh, Uttaranchal state and Ladakh. This is further authenticated by a strong correlation between the melting of Siachen and other Himalayan glaciers like Meola, Gangotri which are already retreating at the rate of more than 30 meters per year.

Siachen and other Himalayan glacier contributed 24 per cent to sea level rise since last 20 years, as reported by the World Glacier Monitoring Service (WGMS) in 2005. On the other hand the western glaciers of Pakistan have remained stable as studies conducted by Italians and the University of Newcastle UK in December 2005, published in the "Annals of Glaciology" duly endorsed. As these glaciers are still safe from human transgression and devilry enacted on Siachen, global warming needs to be re-assessed in this context.

In 2005, the WWF indicated and warned that the Himalayan glaciers, which regulate the water supply to the Ganges, Indus, Brahmaputra, Mekong, Thanlwin, Yangtze and the Yellow Rivers, are believed to be retreating at a rate of about 10-15m (33-49ft) each year. Policy makers and scientists of the subcontinent attributed this unprecedented proof to climatic changes or global warming. Over the past many years though, much publicity has been given and concern expressed over the high level of carbon emission in China and India. Global outcry however continuous to ignore the danger signals emitting from the melting glaciers in the Himalayas. Astonishingly, India ratified the Protocol on Environmental Protection to the Antarctic Treaty in 1996, to preserve the pristine nature of this remote continent, but ignores to protect the Himalayan glaciers. An ADB study reveals that a one-meter sea level rise will displace approximately 7.1 million people in India and the economic impact of climate change on a city like Mumbai could be as high as US $48 billion alone. It was also predicted that cyclones in the Bay of Bengal will increase, while during the post monsoon season, fierce winds will become a regular feature.

Cropping patterns will need to be adapted and water-saving techniques and flood controls introduced, while municipal sewage systems will require redesigning. Other studies anticipate that between 2 to 16 per cent of the gross domestic product (GDP) of South Asian countries will be lost every year due to natural disasters.

It is universally accepted, that the Himalayan Glaciers are not only the 'source of the rivers' and 'ecological source' for China and South-Asia, but also the 'starter' and 'regulating area' for climate control of the Eastern Hemisphere. Himalayan glaciers are the headwater of rivers that feed half of humanity. Asia is significantly affected by the height and extent of the Himalayan mountains as it plays a major role in controlling the climatic system of the region.

In turn, it also affects the global climate change. The glaciers within the Himalayas act as the controlling body of the regional atmospheric circulation and splits the upper westerly winds in winter into northern and southern branches. No-doubt, the glacial changes were recorded during the past century. However in the past 40 years or so, glaciers have shrunk more than 6606 kilometres in the entire region. The greatest retreat became noticeable since the mid 1980s. This indicates that Siachen intervention is already playing havoc with the climate of the South-Asia region.

The melting of Siachen and other glaciers is now significantly contributing to the rising of the oceans. Post-Tsunami research reports concluded that one of the causes that triggered the Indonesian tsunami is the ever-rising sea level. It increases pressure on the earth's crust, causing extreme geological disturbances. Serious alarm bells are raised by American scientists, who warned that Katrina and Rita were the result of pressure on the earth's crust and thus the increase in the rising sea levels. Siachen, still a bone of contention between two countries, needs to be adopted by the world community. With the life of 400million people living within 20 kilometres of the coastlines, the Himalayan glaciers and Siachen need to declared as a global heritage to save them from melting.



The writer is a visiting research fellow at the Sustainable Development Policy Institute in Islamabad. Email: abbasi@sdpi.org