A large number of the valley networks scarring Mars’s surface were carved by water melting beneath glacial ice, not by free-flowing rivers as previously thought, according to new UBC research published today in Nature Geoscience. The findings effectively throw cold water on the dominant “warm and wet ancient Mars” hypothesis, which postulates that rivers, rainfall and oceans once existed on the red planet. To reach this conclusion, lead author Anna Grau Galofre, former PhD student in the department of earth, ocean and atmospheric sciences, developed and used new techniques to examine thousands of Martian valleys. She and her co-authors also compared the Martian valleys to the subglacial channels in the Canadian Arctic Archipelago and uncovered striking similarities. If you look at Earth from a satellite you see a lot of valleys: some of them made by rivers, some made by glaciers, some made by other processes, and each type has a distinctive shape. Mars is similar, in that valleys look very different from each other, suggesting that many processes were at play to carve them.
Antarctic Ice Cores and Environmental Change
Following this maximum, the ice sheet began to diminish in size. Retreat was rapid in some sectors, but was punctuated by still-stands and readvances in other sectors. Geochronology of CIS retreat is key for understanding the pace and style of this deglaciation, and for testing hypothesized feedbacks between the changing ice sheet and the ocean, atmosphere, and solid earth.
One method of reconstructing ice sheet retreat relies on radiocarbon ages of immediate post-glacial organic material. Such ages are minima for deglaciation and are often utilized to infer the timing of ice sheet retreat.
The large polar ice sheets consist of atmospheric precipitation that has fallen over a period ledgfe of accumulation and deformation rates to date the ice core.
Over the past two years, researchers ventured to remote areas along the mountain range to decipher how high ancient glaciers reached, by studying the rocks they left behind. The team collected samples from these glacial deposits, also known as moraines, which are essentially piles of rocks, sand and dirt left behind by flowing ice. By measuring the amount of cosmic radiation the rocks have been exposed to, the research team can map out the reach of ancient glaciers at different points in the past.
Knowing the extent of the ice sheets throughout different climatic conditions over the last 15 million years will offer insights into their possible future as the planet warms from climate change. Their project is supported by the National Science Foundation, which manages the U. Antarctic Program.
Ice core dating using stable isotope data
Ice consists of water molecules made of atoms that come in versions with slightly different mass, so-called isotopes. Variations in the abundance of the heavy isotopes relative to the most common isotopes can be measured and are found to reflect the temperature variations through the year. The graph below shows how the isotopes correlate with the local temperature over a few years in the early s at the GRIP drill site:.
The dashed lines indicate the winter layers and define the annual layers.
They are obtained by drilling through glaciers or ice sheets. have proposed to date ice cores continuously using snow accumulation and ice flow models for.
CN — Scientists have revealed the most detailed map of the land beneath the massive ice sheets of Antarctica — a map that offers significant insight into how the continent will respond to climate change and contribute to rising sea levels, according to a new scientific study. The study, published in Nature Geoscience on Thursday, details how a group of glaciologists assembled the most detailed map to date of the topography hidden beneath Antarctic ice. The group, led by a research team from the University of California, Irvine, used Antarctic ice thickness data that dates back to the late s, comprehensive bathymetry measurements of ice shelves, and several other research tools in their cartography.
The new map, known as the BedMachine project, unearthed several land features that were previously either unknown or poorly understood, according to the study. Significantly, the map revealed icy ridges that help to naturally stabilize ice flow across and around the Transantarctic Mountains, some of the oldest and most expansive mountains in Antarctica. Researchers also gained detailed information on an East Antarctic canyon underneath the Denman Glacier — the deepest land canyon on Earth.
Researchers say that perhaps the most valuable insight that can be gained by this new understanding of Antarctic topography is how the continent could react to continually shifting climate conditions as a result of climate change. It then starts to deform under its own weight forming rivers of ice that discharge icebergs into the ocean. Researchers suggest that with each new discovery made about the geographic makeup of what is under the Antarctic ice sheets, scientists become increasingly well-equipped with the kind of knowledge needed to anticipate and understand how Antarctica will be influenced by climate change in the coming years.
Morlighem said these discoveries were never made by previous radar mapping efforts of Antarctica, and that a newer, more detailed approach was needed in order to make these vital geographic observations. The study notes that while this new map is the most detailed picture scientists have of Antarctica, further efforts to map the landmass could yield even more enlightening results. Skip to content.
An ice core is a core sample that is typically removed from an ice sheet or a high mountain glacier. Since the ice forms from the incremental buildup of annual layers of snow, lower layers are older than upper, and an ice core contains ice formed over a range of years. Cores are drilled with hand augers for shallow holes or powered drills; they can reach depths of over two miles 3. The physical properties of the ice and of material trapped in it can be used to reconstruct the climate over the age range of the core.
The proportions of different oxygen and hydrogen isotopes provide information about ancient temperatures , and the air trapped in tiny bubbles can be analysed to determine the level of atmospheric gases such as carbon dioxide.
Ice cores contribute to our view of Earth’s climate, providing insight into where our Scientists obtain this information by traveling to ice sheets, like Antarctica or the ice accumulates over time allow scientists to date the age of the ice cores.
Review article 21 Dec Correspondence : Theo Manuel Jenk theo. High-altitude glaciers and ice caps from midlatitudes and tropical regions contain valuable signals of past climatic and environmental conditions as well as human activities, but for a meaningful interpretation this information needs to be placed in a precise chronological context. For dating the upper part of ice cores from such sites, several relatively precise methods exist, but they fail in the older and deeper parts, where plastic deformation of the ice results in strong annual layer thinning and a non-linear age—depth relationship.
However such fragments are rarely found and, even then, they would not be very likely to occur at the desired depth and resolution. Since then this new approach has been improved considerably by reducing the measurement time and improving the overall precision.
Ice Sheets and Sea Level in Earth’s Past
Drilling at four sites will go through hundreds of meters of ice before collecting bedrock. Analyzing the isotopes will show when and how the ice receded. Among other things, the researchers will use the new data to test the hypothesis that northern Greenland is more sensitive to warming than the southern part.
The inventory of nitrogen compounds in the polar ice sheets is approximately are used as a component of the layer-counted dating of Greenland ice cores.
Official websites use. Share sensitive information only on official, secure websites. Despite elevated summer insolation forcing during the early Holocene, global ice sheets retained nearly half of their volume from the Last Glacial Maximum, as indicated by deglacial records of global mean sea level GMSL. Partitioning the GMSL rise among potential sources requires accurate dating of ice-sheet extent to estimate ice-sheet volume.
Here, we date the final retreat of the Laurentide Ice Sheet with 10 Be surface exposure ages for the Labrador Dome, the largest of the remnant Laurentide ice domes during the Holocene. We demonstrate through high-resolution regional climate model simulations that the thermal properties of a seasonally ice-free Hudson Bay would have increased Laurentide ice-sheet ablation and thus contributed to the subsequent rapid Labrador Dome retreat. Finally, our new 10 Be chronology indicates full Laurentide ice-sheet had completely deglaciated by 6.
Final Laurentide ice-sheet deglaciation and Holocene climate-sea level change Quaternary Science Reviews. By: David J.
Polar ice caps melting six times faster than in 1990s
Snow and ice play their most important role in the nitrogen cycle as a barrier to land—atmosphere and ocean—atmosphere exchanges that would otherwise occur. The inventory of nitrogen compounds in the polar ice sheets is approximately Tg N, dominated by nitrate in the much larger Antarctic ice sheet. Ice cores help to inform us about the natural variability of the nitrogen cycle at global and regional scale, and about the extent of disturbance in recent decades.
Nitrous oxide concentrations have risen about 20 per cent in the last years and are now almost certainly higher than at any time in the last years.
Ice core , long cylinder of glacial ice recovered by drilling through glaciers in Greenland, Antarctica , and high mountains around the world. Scientists retrieve these cores to look for records of climate change over the last , years or more. Ice cores were begun in the s to complement other climatological studies based on deep-sea cores, lake sediments, and tree-ring studies dendrochronology.
Since then, they have revealed previously unknown details of atmospheric composition , temperature, and abrupt changes in climate. Abrupt changes are of great concern for those who model future changes in climate and their potential impacts on society. Ice cores record millennia of ancient snowfalls, which gradually turned to crystalline glacier ice. In areas of high accumulation, such as low-latitude mountain glaciers and the Greenland Ice Sheet , annual layers of ice representing tens of thousands of years can be seen and counted, often with the unaided eye.
The first deep drilling took place in the s as preliminary efforts at Camp Century, Greenland, and Byrd Station, Antarctica.