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Underwater glacial melting much faster than predicted: Study

WASHINGTON: Underwater melting of tidewater glaciers is occurring much faster than previously thought, according to a study which could lead to improved forecasting of climate-driven sea level rise.

The findings, published in the journal Science, are based on a new method developed by the researchers that for the first time directly measures the submarine melting of tidewater glaciers — valley glaciers that flow all the way down to the ocean.

“Tidewater glaciers around the globe — in Greenland, Alaska, Antarctica and beyond — are retreating and raising sea levels globally,” said Rebecca Jackson, an oceanographer at Rutgers University-New Brunswick in the US.

Submarine melting has been implicated as a trigger for this glacier retreat, but we have had no direct measurements of melting, let alone how it might vary in time,” Jackson said.

The study shows that the prevailing theory for melt significantly underestimates melt rates.

“These results suggest a stronger coupling between the ocean and glacier than previously expected, and our work provides a path forward to improving our understanding of how the ocean impacts glaciers,” she said.

The scientists studied the underwater melting of the LeConte Glacier, a tidewater glacier in Alaska, from 2016-2018.

Most research on the underwater melting of glaciers around the world has relied on theoretical modelling, measuring conditions near the glaciers and then applying theory to predict melt rates, but this theory had never been directly tested, said Dave Sutherland, a professor at the University of Oregon in the US.

The researchers looked for changes in melt patterns between the August and May measurements.

“We found that melt rates are significantly higher than expected across the whole underwater face of the glacier — in some places 100 times higher than theory would predict,” Jackson said.

“We also find, as expected but never shown, that melt rates are higher in summer than in spring, and that variations in melt rates across the terminus cause overcutting and undercutting,” she said.

While the study focused on one tidewater glacier, the new approach should be useful to researchers who study melting at other tidewater glaciers around the world, which would help to improve projections of global sea level rise.

“The fact that we show the existing theory is wildly inaccurate at one glacier — the only glacier where we can make a robust comparison between theory and observations — should lead us to be very sceptical of its current use in studying any tidewater glacier,” Jackson added.

“Our results also align with several recent studies of other glaciers that have indirectly suggested that theory under-predicts melting.

“Our observations prove this in a robust way and contribute to a growing body of research that suggests that we need to revisit our basic assumptions about what controls underwater melting at glaciers around the world,” she said.

Climate change disrupts supply chains — companies investing in responsible energy are resilient: John D St

John D. Sterman teaches at the MIT Sloan School of Management. Speaking to Srijana Mitra Das, he discusses climate impacts on supply chains — and mitigations for greater sustainability:

Q. What is the core of your research?
A. I direct the MIT System Dynamics Group and am co-director of the MIT Sloan Sustainability Initiative. My main research centres on policy to address climate change.

Through our interactive climate policy simulation models, we work with senior leaders in government, business, investing, philanthropy, civil society, education and the public at large in the US and worldwide to help people learn for themselves about the harms from climate change and ways to build a more secure and prosperous future.

Q. New insights from you suggest climate change is already impacting supply chains — can you outline this?
A. We’ve already warmed our world over 1°C above pre-industrial levels. The harms from even that are obvious to all now — these include wildfires, drought, crop yield declines, sea level rise, more extreme storms and flooding and the migration and conflict these create. All these disrupt supply chains through interruptions to sourcing, production, transport and destination markets.

Consumers can expect higher prices and much more volatility in the availability of products as climate change increasingly disrupts the production of commodities.

Q. Are finance and service industry supply chains also climate-vulnerable?
A. Yes. Banks and other financial institutions will experience greater default on loans and higher risk. The cost of capital will rise, slowing investment and economic growth, particularly in emerging and developing nations. Financial markets abhor risk and uncertainty — climate change increases both.

Service industries, like healthcare and tourism, will also be affected. IT consulting, accounting and other service businesses will be impacted as climate change disrupts supply chains for electronics and threatens telecommunications infrastructure.

Q. How can companies protect their supply chains from climate impacts?
A. In the short run, companies need robust emergency plans to safeguard against extreme weather. These may include alternative sources of supply and strategic inventory accumulation. ‘Just in time’ works well when material and component supplies are steady and reliable — but this is now a brittle system with low resilience to increased risks of supply disruptions.

These plans should therefore assume more severe disruptions, happening more often and with more weather events hitting at once than actuarial estimates would indicate. Many communities have experienced multiple ‘100-year storms’ in just the last decade — so, historical experience is a poor guide to future risk in a rapidly warming world.

But the most important immediate action for companies and countries is to reduce their greenhouse gas emissions as quickly as possible — without such cuts, global warming will continue, threatening our prosperity and security. The world’s poor will not be able to rise out of poverty. Instability will increase and the harm to businesses and people will be profound. There is no time to waste.

Furthermore, companies that cut their dependence on fossil fuels by investing in efficiency and renewable energy increase their own resilience — they will be less vulnerable to disruptions in energy supply and wild swings in energy prices due to the physical harms from climate change and transition risks as governments impose policies that will raise costs and reduce the availability of coal, oil and methane gas.

Finally, companies must not only work to cut their own emissions and those of their supply chain partners, they must demand that governments enact policies to phase out fossil fuels as swiftly as possible and promote renewable energy.

To succeed in a warming world , businesses need reliable, renewable, responsible sources of zero-carbon energy. Government policy is essential in providing this infrastructure that will reduce business risk and uncertainty, fostering sustainable development and a healthy business sector.

Q. Have companies already begun applying climate mitigation strategies?
A. Apple, Amazon, Microsoft, Walmart, General Motors and many other global leaders in business have committed to achieve net zero emissions by midcentury or even sooner.

The real estate industry has discovered that highly efficient green buildings have lower operating costs — these cost only 0-5% more than conventional buildings, are more comfortable, boost worker productivity and are more resilient to climate-fuelled storms. That’s why green buildings rent and sell at premia compared to traditional buildings.

Q. How do the climate change simulations you’ve devised help companies understand the situation before them?
A. With our partner, the non-profit think tank, Climate Interactive, we have developed interactive simulations of the energy system, economy and climate. The En-ROADS simulation enables you to learn for yourself about the climate and energy system. You can try any actions and policies you like and discover which can help limit climate change and which are low-leverage or too little, too late.

Elected officials, senior company leaders and civil society representatives are using En-ROADS to learn how they can help create a more sustainable world. Try it yourself at http://en-roads.org

Views expressed are personal