My Science School

Walruses, often found lying on the ice in the Arctic Circle, are massive marine mammals. Their distinctive features are their long, white tusks. The tusks are actually their upper canine teeth that grow all through their lives. Both males and females have tusks which they use to break through ice and haul their huge bodies out of frigid waters.

Both sexes possess long tusks (the upper canine teeth) that project downward from the mouth. In the male they can grow to about a metre in length and 5.4 kg (12 pounds) in weight. The tusks function mainly in mating display and in defense against other walrus. They are not used to dig food from the ocean floor. The walrus feeds at depths of less than 80 metres (260 feet), usually at 10–50 metres (30–160 feet). Rooting along the ocean floor with its snout, it identifies prey with its whiskers. The walrus’s diet consists largely of clams and mussels but occasionally includes fish and even small seals.

The walrus is valued by both the Inuit and commercial hunters for blubber, hide, and ivory tusks. Its numbers have been reduced by commercial operations. Walrus are now protected from sealers but are still subject to subsistence hunting by aboriginals. Like seals, the walrus is a pinniped. It is the sole living member of the family Odobenidae.

Credit : Britannica

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Swans were regarded as a status symbol as well as a delicacy in medieval England. According to medieval legislation, the Queen owns all unmarked mute swans on "certain stretches of the Thames and its surrounding tributaries." To this day during the third week of July, all the swans on the Thames are counted for the Queen in a practice called Swan Upping. It is held not just to establish the ownership of each swan, but also to check up on their health and to conserve their population.

Swans—who owns them, who breeds them and who eats them—is an issue for the British that has generated legal statutes, sparked courtroom battles and engaged town councils in bitter arguments since the Middle Ages. 

There is a legend that the mute swan was introduced to Britain by Richard I in the 12th century, who brought them back from his campaigns during the Crusades. Today, ornithologists believe the bird is probably native to the country, with archaeological evidence for the presence of swans dating back as far back as the late glacial period, 10,000 years ago.

Since ancient times, swans have been associated with tranquility and nobility, featuring in myths and stories around the world. Their high status is likely to have come about because of their perceived beauty and natural behavior; they are solitary birds, strong and aggressively protective of their young but at the same time graceful and elegant on the water.

Swans were luxury goods in Europe from at least the 12th century onward; the Medieval equivalent of flashing a Rolex or driving a Lamborghini. Owning swans signaled nobility, along with flying a hawk, running hounds or riding a battle-trained destrier. Swans were eaten as a special dish at feasts, served as a centerpiece in their skin and feathers with a lump of blazing incense in the beak. They were particularly associated with Christmas, when they would be served in large numbers at royal feasts; forty swans were ordered for Henry III’s Christmas celebrations in 1247 at Winchester, for example.

Credit : Smithsonian Magazine

Picture Credit : Google

Stingray is a kind of cartilaginous fish that lives in the shallow waters. It has a flat body. It’s skeleton is made up of cartilages (just like your ears). While its eyes are located on the dorsal side, my mouth, nostrils, and gill slits are situated on its underbelly.

It is an ovoviviparous creature. That is, the young are hatched from eggs held within the body of the female.

It is not usually aggressive and it attacks humans only when provoked. Contact with the stinger causes local trauma, pain and swelling. The sting may become fatal only if the affected area is a vital organ.

Stingrays use a super set of senses to search for food. Special gel-filled pits across the front of their face, (called Ampullae of Lorenzini), allow them to pick up electrical signals from other animals when they move – cool! Their eyes are on the topside of their body and their mouth and gills can be found underneath, so in the darker depths or murky rivers this electromagnetic sense is especially useful for searching for prey.

Picture Credit : Google

Our Earth is a water world. It is the availability of water that makes our planet unique in the solar system. Approximately 71% of the earth's surface is covered by water. The oceans and the seas account for 97%. The rest exists as lakes and rivers, as glaciers and ice caps, and as aquifers. This is so enormous an area that any amount of knowledge of the science and geography of water sources wouldn't be enough. There are different forms of studies such as hydrology, oceanography and limnology that try to understand water and water bodies. And today, we are going to focus on hydrography.

What is hydropgraphy? In the past, ships were one of the major transport systems - they ferried people and goods across the world. But they often ran aground or overturned after striking an underwater rock or mudbank. The need to know the geography of the ocean floors, thus, was strongly felt. Individual mariners began to make charts and describe the bodies of the water to aid navigation. Today, surveyors use technology to map the sea floor. and scientifically and systematically measure and describe the physical features of bodies of water, including the ocean, coastal zones, rivers, and lakes. This is called hydrography.

Hydrography involves measuring the depth of the water and fixing the position of all the navigational hazards that lie on the senfloor, such as: wrecks and rocks. That data is used to update nautical charts and develop hydrographic models Hydrography also involves measuring the tide and the currents

Hydrography comprises two distinct branches. While marine hydrography is the study of the ocean floor, the coasts, tides and currents, hydromorphometric is dedicated to the study of river basins their shapes, dimensions and composition. The second branch helps us apply the knowledge for irrigation, river navigation and power generation.

Today, hydrographic maps are important in informing ocean resource management policies, predicting geohazards, and characterising habitats. Some hydrographers also study the physical and chemical properties of the sea and other water bodies, such as temperature, dissolved oxygen, and salinity.

How is hydrography done?

Surveying with multibeam echo sounders is the primary method of obtaining hydrographic data. The beams sweep the seafloor and bounce off details of the depth of the surveyed area. Sonan, aircraft fitted with lasers and satellite observations are also used in hydrography.

Picture Credit : Google

The Intergovernmental Panel on Climate Change's (IPCC) Sixth Assessment Report (AR6) 'Climate Change 2021: The Physical Science Basis' was released recently. The report was approved by 195 member governments of the IPCC through virtual sessions held over two weeks in July and August. The report pointed out that every region in the world is witnessing irreversible changes in climate due to human influence. Sea level rise, floods, heavy rainfall and glacier melting are some of these irreversible effects. The report warned that extreme sea level events that previously occurred once in 100 years could happen every year by the end of this century.

Using the extensive data on future sea level rise from the IPCC, the National Aeronautics and Space Administration (NASA) of the United States has created a visualisation tool accessible to the public. The tool allows users to view both global and regional sea level projections from 2020 to 2150, along with how these projections differ depending on future scenario. Users can click on a point anywhere in the ocean to obtain the IPCC projection of sea level for that individual location.

As for India, the NASA tool predicts some grim future. The rising sea level threatens to submerge at least 12 coastal cities in the country. What are these cities and how grave is the threat? What causes sea level rise?

What does the tool predict for Indian cities?

From Okha in Gujarat to Khidirpur in Kolkata, the NASA tool offers sea-level projection for 12 Indian coastal cities, which are likely to sink nearly three feet underwater by 2100. Refer the table here to see how your city fares.....

What does the report say about global sea level rise?

By 2100, the global mean sea level will rise between 1.3 feet and 2.6 feet. How high the seas rise depends on how much and how quickly we manage to cut greenhouse gas emissions, the report says.

What is the IPCC report all about?

The Intergovernmental Panel on Climate Change is a climate-science-focused organisation of the United States. It's been around since 1988, and it has 195 member countries. Every seven years or so, the IPCC releases a report summarising the most up-to-date, peer-reviewed research on the science of climate change, its effects and ways to adapt to and mitigate it.

The purpose of these reports is to provide everyone, particularly governing bodies, with the information they need to make important decisions regarding climate change. The IPCC essentially provides governments with thousands of papers published regarding the science, risks, and social and economic components of climate change.

The report released this month was authored by 234 scientists nominated by IPCC member governments around the world. These scientists are Earth and climate science experts.

What causes sea-level rise?

Global warming: The burning of fossil fuels, deforestation, decomposition of waste in landfills and livestock have released enormous amounts of greenhouse gases into the atmosphere. These emissions have caused the Earth's surface temperature to rise, causing global warming, which leads thermal expansion and melting of glacier, and thereby directly contribute to sea-level rise.

Thermal expansion

The oceans are absorbing more than 90% of the increased atmospheric heat associated with greenhouse gas emissions. When water heats up, it expands. The ocean water expands to fill a greater volume and takes up more space. This is called thermal expansion, and it is responsible for one-third of the sea-level rise, according to studies.

Melting of glaciers and ice caps

Warmer temperatures cause land-based ice, such as glaciers and ice sheets to melt, and the meltwater flows into the ocean to increase sea level. Melting ice causes about two-thirds of the rise in sea level.

How does sea-level rise impact coastal regions?

• The impact of sea-level rise includes flooding of coastal areas, increased soil erosion, disappearance of low-lying islands, saltwater intrusion and habitat destruction in coastal areas. Rising sea levels also make storm surges capable of much greater damage. (Storm surge is the abnormal rise in seawater level during a storm. Storm surge can penetrate well inland.)
• Higher sea levels are coinciding with more hurricanes, contributing to more powerful storm surges that can strip away everything in their path.
• Saltwater intrusion is the flow of seawater into water bodies such as rivers and aquifers (underground waterbearing rocks). It is a major concern as it can induce contamination of water resources, used for drinking, household purposes and agriculture. Increased salinity of coastal freshwater can threaten vegetation and wildlife of the region.
• Many birds use coastal ecosystems to find food, live and breed. Sea turtles lay their eggs on beaches, returning to the same location every year. When beaches erode, these animals and birds will be affected.
• Islands and island life will be particularly affected due to sea level rise.
• Rising sea levels will lead to the displacement of people. It could create 187 million climate refugees by 2100, according to a study.

What are the important takeaways from the report?

• The report says almost all of the warming that has occurred since pre-industrial times was caused by the release of heat-trapping gases such as carbon dioxide and methane. Much of that is the result of humans burning fossil fuels - coal, oil, wood and natural gas.
• The global temperatures have already risen by 1.1 degrees Celsius since the 19th century, reaching their highest in over 100.000 years, and only a fraction of that increase can have come from natural forces.
• The report concludes that ice melt and sea level rise are already accelerating. Wild weather events from storms to heat waves are also expected to worsen and become more frequent.
• Even if emissions are drastically cut, some changes will be "irreversible" for centuries, the report said.
• While many of the report's predictions paint a grim picture of humans' impact on the planet and the consequences that will have going forward, the IPCC also found that so-called tipping points, like catastrophic ice sheet collapses and the abrupt slowdown of ocean currents, are "low likelihood," though they cannot be ruled out.
• Although temperatures are expected to overshoot the 1.5 degree Celsius target in the next decade, the report suggests that warming could be brought down through "negative emissions." (Negative emission is the removal of more carbon dioxide out of the atmosphere than is added) But many scientists are sceptical about this mitigation measure.
• The assessment shows the ocean surface has warmed slightly less, by about 0.9 degree Celsius as a global average, than the land surface since 1850, but about two thirds of the ocean warming has taken place during the last 50 years. It is certain that the heat content of the ocean will continue to increase until at least 2300, even under low emissions scenarios.
• Carbon dioxide emissions are the main driver of acidification in the open ocean, Oxygen levels have dropped in many ocean regions since the mid 20th century and marine heatwaves have doubled in frequency since 1980, also becoming longer and more intense, says the report.

Picture Credit : Google