Brian Stewart surveying the extensive scatters of stone artefacts observed along the margin of a now-dry lakebed near Swartkolkvloer.  CREDIT Brian Chase
Brian Stewart surveying the extensive scatters of stone artefacts observed along the margin of a now-dry lakebed near Swartkolkvloer. CREDIT Brian Chase

Dr. Andrew Carr models ancient climate change to solve the mystery of vanished South African lakes

New evidence for the presence of ancient lakes in some of the most arid regions of South Africa suggests that Stone Age humans may have been more widespread across the continent than previously thought. 

Research jointly led by the University of Leicester in the UK argues that more archaeological work in the interior regions of South Africa – a country renowned for its globally-significant archaeological record – may reveal more about our ancient ancestors and their movements. Andrew Carr collecting sediment samples dating to the Last Glacial Maximum from the dry lakebed at Swartkolkvloer.  CREDIT Brian Chase

South Africa’s Stone Age archaeological record, particularly for the last 150,000 years has been the subject of a great deal of investigation, not least due to the presence of several remarkable coastal caves and rock shelter records. However, the presence of humans and the resources available to them in the vast interior regions of the country have thus far remained much more enigmatic. 

New research by an international team of researchers from South Africa, the United Kingdom, the United States, and France suggests several large bodies of water were sustained in the now arid South African interior during the last Ice Age, particularly 50,000-40,000 years ago, and again 31,000 years ago. Importantly, the group was able to model how much water was required to fill these palaeo-lakes, allowing the climatic changes necessary to create lakes, and the resulting impacts on the region’s hydrology, flora, and fauna, to be reconstructed. 

Their findings paint a picture of a diverse and fertile region that would have been capable of supporting hunter-gatherer communities of the time.

Team member Dr. Andrew Carr from the University of Leicester School of Geography, Geology and the Environment said: “This is currently the best evidence for when these lakes existed. This region has been something of a gap on the map, climatically and archaeologically. We know humans were present at times during the last ice age, as archaeological materials are scattered across the landscape surface. This new work hints at when and why humans used this landscape. 

“These areas look inhospitable today, but were seemingly much less so at times in the past, and this has implications for when and how groups of people used the landscape and potentially how they were connected and exchanged ideas.

“It also tells us something about the sensitivity of ecosystems and environments to global climatic change. You can see how these desert landscapes can respond in quite significant ways to global climate changes, and understand how the human species responded and how adaptable it would have been.”

The scientists studied three lakes from the arid western interior of South Africa to as far east as Kimberley. As well as dating shorelines using radiocarbon and luminescence dating methods, they estimated the lake sizes and capacities. Supercomputer models of regional hydrology showed that the conditions necessary to create the studied lakes would have led to widespread changes in the region’s many (presently ephemeral) rivers and lakes as the water table rose. 

Dr. Carr added: “The next step is to start to look for sites where we can do more direct dating of the occurrence of stone tools in this region. The work shows that at times the region offered a range of resources and the archaeological ‘gap on the map’ is much more likely to reflect the lack of sites preserving deep archaeological deposits. 

“The region is quite challenging for archaeology as most materials lie in the open on the desert surface with no stratigraphic context - hence it's very difficult to know how long it's been there.” 

UK space missions set to improve solar storm forecasts

Satellites launched into outer space could send back improved warnings of dangerous solar storms thanks to a breakthrough in the way scientists use space weather measurements.   

Experts from the University of Reading have found that using satellite data that is less reliable but is returned to Earth rapidly can be used to improve the accuracy of solar wind forecasts - which are harmful streams of charged particles sent from the sun - by nearly 50 percent.

Their research, published today in Space Weather, could pave the way for agencies, such as the Met Office, to provide more accurate forecasts for severe space weather, which can cause blackouts and harm human health.

Lead researcher Harriet Turner, from the University of Reading’s Department of Meteorology, said: “We know lots about how to prepare for storms that form on Earth, but we need to improve our forecasts of the dangerous weather we get from space. Space weather threatens our technology-focused way of life as it can cause power grids to fail, damage satellites, such as GPS, and even make astronauts ill. 

“Our research has shown that using rapid satellite measurements to forecast space weather is effective. By sending spacecraft far from Earth, we can use this new technique to get better solar storm predictions and ensure we are prepared for what’s to come.”

Simon Machin, Met Office Space Weather Manager, said: “This is a great example of the value that can result through our collaboration with academia. By pulling through scientific research into the operational domain, improved space weather forecasting will ultimately enhance our nation's ability to prepare for and mitigate against space weather events.”

Old dogs and new tricks

To predict space weather, scientists need to forecast the solar wind conditions on Earth. To do this, they combine supercomputer simulations with observations from space to estimate what space weather will be like. This is known as data assimilation. The highest quality observations only become available many days after they are made, as they are processed on the ground and ‘cleaned’, meaning forecasts take longer to achieve.  

To obtain forecasts faster, the research team tried using near-real-time (NRT) data. NRT data undergo no processing or cleaning, meaning it is less accurate but can be made available within a couple of hours. The research team found that forecasts produced using the NRT data still produce reliable predictions and enable greater warning time. This could enable authorities to better prepare for power failures that cost up to 2.1 trillion dollars over a century in the USA and Europe. 

To the stars

The scientists behind this new study say using this new technique with upcoming space missions will enable better forecasts.

The European Space Agency (ESA) will launch ‘Vigil’ in the mid-2020s, a first-of-its-kind mission that will monitor potentially hazardous solar activity using several UK-built instruments. 

By launching the spacecraft into a position 60 degrees behind Earth in longitude, the Met Office will be able to improve space weather forecasts by using data assimilation of the NRT solar wind data. 

It is hoped the unique location of Vigil will allow scientists to see the solar wind that will later arrive at Earth, maximizing forecast accuracy and warning time.

Figure 1 of Wang Z, Liu C, Cheng C, Qin Q, Yan L, Qian J, Sun C, Zhang L. On the Multiscale Oceanic Heat Transports Toward the Bases of the Antarctic Ice Shelves. Ocean-Land-Atmos. Res. 2023;2:Article 0010.  CREDIT Wang Z, Liu C, Cheng C, Qin Q, Yan L, Qian J, Sun C, Zhang L.
Figure 1 of Wang Z, Liu C, Cheng C, Qin Q, Yan L, Qian J, Sun C, Zhang L. On the Multiscale Oceanic Heat Transports Toward the Bases of the Antarctic Ice Shelves. Ocean-Land-Atmos. Res. 2023;2:Article 0010. CREDIT Wang Z, Liu C, Cheng C, Qin Q, Yan L, Qian J, Sun C, Zhang L.

Chinese researcher's simulations show why Antarctic ice shelves are losing their mass, how it leads to global sea level rise

Many nuances factor into the behavior of large ice sheets in the Earth’s oceans; these nuances and the progress toward understanding and accurately simulating these behaviors are being reviewed in this study

The Greenland ice sheet (GIS) and Antarctic ice sheet (AIS) contribute largely to global mean sea level (GMSL) changes, though the seas surrounding the Antarctic like the Bellinghausen-Amundsen Seas and the Indian Ocean sector are seeing significantly more warming than the rest of the marginal seas, with immediately noticeable effects on the mass balance (net weight of the glacier mainly accounting for ice gained by snow and lost by melting and calving) of the AIS. The level AIS will contribute to the overall increase in sea level is unknown, and current models vary drastically, leaving a major question regarding future sea levels unanswered. The development of accurate modeling and technology that can help predict the future state of the Earth’s oceans and ice sheets will help answer these questions.

“In this paper, we identify key multiscale oceanic processes that are responsible for heat delivery to the bases of the Antarctic ice shelves and review our current understanding of these processes,” said Zhaomin Wang, professor and first author of the study.

One of these processes responsible for heat delivery is circumpolar deep water (CDW). Fig. 2. Map of the Antarctic continent and the Southern Ocean. The color shading is the seafloor topography of the Southern Ocean and the Antarctic marginal seas. Light blue color represents the Antarctic Ice Shelves. Colored lines indicate the locations of the cross sections in Fig. 4 for 3 typical shelf regions: a cold and fresh shelf (118°E; cyan), a cold and saline shelf (35°W; green), and a warm and saline shelf (100°W; red).

CDW is a mix of the ocean’s water masses from different ocean basins, culminating in a warm, salty mass of water in the Southern Ocean. This water can cut through the base of ice shelves rapidly, leading to “cavities”, or cleaves in a glacier due to warm water currents. These cavities are then filled with warm-modified CDW and high salinity shelf water which eventually leads to the loss of chunks from the tip of the glacier, known as “calving”. CDW and cavity development are substantial processes, along with basal melting and calving, in which the AIS loses its mass and consequently is a significant contributor to the rise in GMSL.

The effects CDW has on the melting of Antarctic ice shelves, along with other mechanisms contributing to warm air and water circulation, are generally understood though they are poorly modeled with consistency. This may be due to not understanding small-scale processes, particularly when it comes to the effects eddies (short-lived oceanic circulation patterns) and the topography of cavities in the glacier have on melting.

“Both eddies and the dynamic effects of bottom topography have been proposed to be crucial in heat transport toward the fronts of ice shelves, in addition to heat transport by coastal currents,” Wang said. 

These topographical subtleties help with understanding the transport of CDW and how coastal currents, surface winds, and bottom pressure torque all play into the interactions of these warm water currents with glacial masses and ice sheets.

In review, ice melting thanks to warm water aren’t as simple as it seems on the surface. Researchers surmised that while progress in learning the mechanisms in which oceanic warming is affecting the AIS is occurring, there needs to be improvement and innovation to assess where the continued melting of ice shelves in the Antarctic will leave humanity in the future. Retreating coastlines and GMSL rise are anticipated, though the levels to be expected are poorly understood.

Researchers suggest priorities are made, starting with improving cavity geometry, bathymetry (measuring the depth of water), and future projections of the mass balance of ice sheets. Spending time investigating small-scale processes may also provide valuable information leading to better future models being developed, and critically, determining what the mass loss of the AIS means for atmospheric, oceanic, and sea ice circulations.

China National Natural Science Foundation Projects, The Independent Research Foundation of Southern Marine Science and Engineering Guangdong Laboratory, and the National Science Foundation of Jiangsu Province made this research possible through funding.

Zhaomin Wang, Chengyan Liu, and Chen Cheng of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai), Qing Qin, Liangjun Yan, Jiangchao Qian, and Chong Sun of College of Oceanography at Hohai University, and Li Zhang of the School of Atmospheric Sciences at Sun Yat-sen University contributed to this research.