Environment

Clouds Over Southern Ocean Made by Ocean Creatures

The Southern Ocean is reckoned as the cloudiest region in our planet and it almost nearly blanketed all through the year. But it might be surprising that it is the tiny marine organisms known as Phytoplankton that live in the stormy waters of the ocean that are responsible for creating these clouds.

Measuring how the gases and particles emitted by these tiny creatures entered the atmosphere to become cloud seeds was the subject of a recent study. This study was also the first large scale correlation between cloud formation and biological activity in the Southern ocean. Establishing that link constitutes a significant first move towards understanding the role played by clouds and the tiny particles of air known as aerosols in the context of climate change and climate modelling.

In climate models, aerosols and clouds constitute two important wild cards and comprehending their impact on climate gets further complex when we consider the question of how they interact with each other. Soot is a type of aerosol that comes from human activities, but we also have other natural aerosols like sulphate, sea spray and ammonium salts in the atmosphere. All these particles form the ‘seeds’ and water vapour condenses around these to become tiny droplets and turn into clouds.

Clouds can have a key role when we consider climate – but that role is complicated. The planet tends to get cooled by the low lying clouds that functions as reflectors and bouncing the solar radiation back to space. Higher clouds on the other hand tend to trap the heat and prop up warming. Climate models in the Southern Ocean have been pretty poor in capturing the influence of the clouds by estimating less reflected radiation than what actually exists. Scientists will have to understand more about aerosols that help in formation of the clouds and how they have impacted the climate over the past 2 centuries, to improve these models. But the task gets difficult for tracking in the absence of knowledge on the number of ‘natural’ aerosols present in the atmosphere before industrialisation began.

If concentration of aerosols were higher during the preindustrial times, then the impact from human perturbations to aerosols would be smaller.

This also brings into focus the Southern Ocean. Apart from being the cloudiest place on the planet, it is also one among the cleanest and relatively unharmed by human activity. That makes it the perfect laboratory for examining the interaction between cloud and aerosols.

Environment

Global Warming Shifts Heavy Rainfall Times in the UK.

The United Kingdom is one of those places that have been studying their weather and rainfall patterns for ages, with huge numbers of rain gauges scattered all across the country. Using this wealth of information, researchers have found that as the global climate warms the time of year when the UK will receive it’s heaviest rainfall is set to shift.

The research found in two different models that between 2021 and 2060 and 2061 and 2100 the south-east of the country is likely to experiences its extreme rainfall in autumn rather than in late summer, while the north-east of the country will see its heaviest rainfalls a month earlier than currently.

Problematically, these changes shift the heavy rainfalls over into times when the water catchments are already at their maximum capacity, increasing the risk of flooding in the regions.

The change in rainfall patterns would also affect the viability of many food and forage crops grown in the UK.

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Forests Worldwide Near Tipping-Point From Drought.

A new study, conducted by an international team of scientists, assessed the specific physiological effects of drought on 226 tree species at 81 sites in different biomes around the world. It found that 70 percent of the species sampled are particularly vulnerable to reduction in water availability. With drought conditions increasing around the globe due to climate change and deforestation, the research suggests large swathes of the world's forests — and the services they afford — may be approaching a tipping point.

Water is critical to trees, transporting nutrients, providing stabilizing, and serving as a medium for the metabolic processes that generate the energy needed for a tree to survive. Insufficient water availably leads a tree to start pulling air bubbles — called gas emboli — into its xylem impeding the flow of water. Hydraulic failure is akin to attempting to drink through a broken straw — air bubbles significantly reduce the amount of liquid that reaches the top of the straw.

The researchers found that a wide range of trees are susceptible to "hydraulic failure".

The study provides insight on why drought-induced forest die-off is occurring in a range of forest types, including tropical rainforests which are not typically considered at risk of drought. Over the past 15 years, forests in Borneo and the Amazon have suffered from widespread drought-induced decline. Drought stress if often accompanied by increased incidence of fires, either from natural sources like lightning or human activities like burning for cattle pasture of plantation establishment.

The suggestion that all forests are on the brink of succumbing to drought, and may already be responding to climate change, is supported by observations of increased drought-induced forest die-offs and tree mortality in many ecosystems.

The research also has implications for efforts to combat climate change by relying on forests to sequester more carbon from the atmosphere. Dying forests release, rather than absorb, carbon.

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Sea snails show impact of more acidic ocean.

The shells of some marine snails in the seas around Antarctica are dissolving as the water becomes more acidic, threatening the food chain,

Oceans soak up about a quarter of the carbon dioxide released into the atmosphere each year and as CO2 levels in the atmosphere increase from burning fossil fuels, so do ocean levels, making seas more acidic.

Ocean acidification is one of the effects of climate change and threatens coral reefs, marine ecosystems and wildlife.

It has been found thattThe shell of the pteropod sea snail in the Southern Ocean was severely dissolved by more acidic surface water.

And although the snails did not necessarily die, it increased their vulnerability to predators and infection which could affect other parts of the food chain. The sea snails are an important source of food for fish and birds as well as an indicator of marine ecosystem health.