Sentences with phrase «changes over ice sheets»

As a remote sensing scientist, I often use Worldview to put things into context (e.g. for studying changes over ice sheets and glaciers).

Not exact matches

Developing an understanding of how ice sheets are changing over time requires precise measurements of the thickness of the ice sheets and accurate mapping of the bedrock below.

Stewart Jamieson from Durham University in England and his colleagues made the discovery by looking for subtle changes in the ice sheet's surface shapes, developed as a result of ice flowing over diverse topography.

«It is a very good paper which provides valuable new insights about the physical processes controlling the change in reflectivity of the Greenland ice sheet and specifically its darkening over time,» said Eric Rignot, a senior research scientist at NASA's Jet Propulsion Laboratory who studies ice sheets but was not involved with the new study.

«It doesn't change our estimates of the total mass loss all over Greenland by that much, but it brings a more significant change to our understanding of where within the ice sheet that loss has happened, and where it is happening now.»

The team found layers of sediment and rocks that built up over time, recording the flow of the ice sheet and reflecting climate change.

«It turns out that for much of the East Antarctic Ice Sheet's history, it was not the commonly perceived large stable ice sheet with only minor changes in size over millions of years,» he saIce Sheet's history, it was not the commonly perceived large stable ice sheet with only minor changes in size over millions of years,» he Sheet's history, it was not the commonly perceived large stable ice sheet with only minor changes in size over millions of years,» he saice sheet with only minor changes in size over millions of years,» he sheet with only minor changes in size over millions of years,» he said.

A new study by scientists at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, and the University of California, Irvine, shows that while ice sheets and glaciers continue to melt, changes in weather and climate over the past decade have caused Earth's continents to soak up and store an extra 3.2 trillion tons of water in soils, lakes and underground aquifers, temporarily slowing the rate of sea level rise by about 20 percent.

From an altitude of just over 700 km, CryoSat will precisely monitor changes in the thickness of sea ice and variations in the thickness of the ice sheets on land.

To consider change in the ice sheet over time, we also need to know how the inputs change over time.

GRACE - FO and ICESat - 2 will use radically different techniques to observe how the massive ice sheets of Greenland and Antarctica are changing over time and how much they are contributing to sea level rise.

That estimate was based in part on the fact that sea level is now rising 3.2 mm / yr (3.2 m / millennium)[57], an order of magnitude faster than the rate during the prior several thousand years, with rapid change of ice sheet mass balance over the past few decades [23] and Greenland and Antarctica now losing mass at accelerating rates [23]--[24].

Antarctic climate and ice sheet changes and their relationship to global scale climate change over the last 2000 years.

[Response: Here's a simple back - of - envelope consideration for the future: if the Greenland ice sheet melts completely over the next ~ 1,000 years (Jim Hansen argues in the current Climatic Change that the time scale could be centuries), this would contribute an average flux of ~ 0.1 Sv of freshwater to the surrounding ocean.

Most geologic sea level changes are related to tectonic processes (rates of ocean spreading, continental subduction etc.) or the waxing and waning of ice sheets (particularly over the last 2.5 million years).

In a more recent paper, our own Stefan Rahmstorf used a simple regression model to suggest that sea level rise (SLR) could reach 0.5 to 1.4 meters above 1990 levels by 2100, but this did not consider individual processes like dynamic ice sheet changes, being only based on how global sea level has been linked to global warming over the past 120 years.

• Thorough understanding of the physics and dynamics of the Greenland and Antarctic ice sheets, with a view to predicting sea level rise within 20 % for a specified change in climate over the ice sheets....»

The largest climate mode shift over this time interval, occurring ~ 950,000 years before the present (the mid-Pleistocene transition), has previously been attributed to changes in the pattern and frequency of ice sheets.

Ricarda Winkelmann et al. modeled the response of the Antarctic ice sheet to a wide range of future carbon emissions scenarios over the long - term (previous simulations have mainly looked at changes that might occur on a shorter timescale).

With global GHG emissions and concentrations continuing to increase; with climate change intensifying changes in ecosystems, ice sheet deterioration, and sea level rise; and with fossil fuels providing more than 80 % of the world's energy, the likelihood seems low that cooperative actions will prevent increasingly disruptive climate change over the next several decades.

Figure 3: Estimated ice mass change over time for the entire Antarctic ice sheet, West Antarctica, West Antarctica without the rapidly changing Amundsen Sea Coast (ASC) region and East Antarctica.

Then in 2003 the launch of two new satellites, ICESat and GRACE, led to vast improvements in one of the methods for mass balance determination, volume change, and introduced the ability to conduct gravimetric measurements of ice sheet mass over time.

Ritz, C., Rommeleare, V. & Dumas, C. Modeling the evolution of Antarctic ice sheet over the last 420,000 years: implications for altitude changes in the Vostok region.

Ice sheet feedbacks seem the dominant mechanism for abrupt change over the Quaternary.

A simple ice budget calculation from ESL records demonstrates that the change in ice volume over Antarctica during the Late Glacial was at least comparable with the Scandinavian ice sheet, and quite possibly larger.

«Models traditionally have projected that this difference doesn't become negative (i.e. net loss of Antarctic ice sheet mass) for several decades,» Mann said, adding that detailed gravimetric measurements, which looks at changes in Earth's gravity over spots to estimate, among other things, ice mass.

The objects would have exploded over North America or slammed into it, or both, shattering and melting ice sheets, sparking extreme wildfires, and fueling hurricane - force winds — all of which could have contributed to changes in climate that led to the cooling of the Younger Dryas period.

When there is evidence for the growth of a large ice sheet on Antarctica or on Greenland or the growth of sea ice in the Arctic Ocean, we see evidence for a dramatic change in carbon dioxide levels over the last 20 million years.

16 * Melting Glaciers and Rising Sea Levels Over the last century glaciers have been melting worldwide Antarctica ice sheet temp has risen 6 degrees As ice sheets and glaciers melt, sea level rises * Regional Temp Changes Changes in regional climate * Drought and Desertification Rising temps causes regions to warm and become very dry.

Since there is controversy over the subject of climate change, it is important to study the behaviour of ice sheets in the past, in order to predict what may happen in the futureThe study focused on «erratic» rocks, which are rocks that differ totally from the local sedimentary rocks and have been transported there by moving ice.

In addition, the running sum total of the accumulated mass change over the Greenland Ice Sheet is shown on a graph overlay in gigatons.

Actually Fielding's use of that graph is quite informative of how denialist arguments are framed — the selected bit of a selected graph (and don't mention the fastest warming region on the planet being left out of that data set), or the complete passing over of short term variability vs longer term trends, or the other measures and indicators of climate change from ocean heat content and sea levels to changes in ice sheets and minimum sea ice levels, or the passing over of issues like lag time between emissions and effects on temperatures... etc..

NASA is carrying out its sixth consecutive year of Operation IceBridge research flights over Antarctica to study changes in the continent's ice sheet, glaciers and sea ice.

«The observed changes in sea ice on the Arctic Ocean, in the mass of the Greenland ice sheet and Arctic ice caps and glaciers over the past 10 years are dramatic and represent an obvious departure from long - term patterns,» says the report.

In addition there are slow climate feedbacks, such as changes of ice sheet size, that occur mainly over centuries and millennia.

That estimate was based in part on the fact that sea level is now rising 3.2 mm / yr (3.2 m / millennium)[57], an order of magnitude faster than the rate during the prior several thousand years, with rapid change of ice sheet mass balance over the past few decades [23] and Greenland and Antarctica now losing mass at accelerating rates [23]--[24].

Joughin and others, 2008 observed that seasonal drainage of meltwater to the glacier bed induces a uniform acceleration of 50 — 150 meters / year over a ~ 300 km long section of the West Greenland margin that is not drained by outlet glaciers, causing a large fractional acceleration of the interior ice sheet but a small fractional change in the speed of fast - moving outlet glaciers.

Since to me (and many scientists, although some wanted a lot more corroborative evidence, which they've also gotten) it makes absolutely no sense to presume that the earth would just go about its merry way and keep the climate nice and relatively stable for us (though this rare actual climate scientist pseudo skeptic seems to think it would, based upon some non scientific belief — see second half of this piece), when the earth changes climate easily as it is, climate is ultimately an expression of energy, it is stabilized (right now) by the oceans and ice sheets, and increasing the number of long term thermal radiation / heat energy absorbing and re radiating molecules to levels not seen on earth in several million years would add an enormous influx of energy to the lower atmosphere earth system, which would mildly warm the air and increasingly transfer energy to the earth over time, which in turn would start to alter those stabilizing systems (and which, with increasing ocean energy retention and accelerating polar ice sheet melting at both ends of the globe, is exactly what we've been seeing) and start to reinforce the same process until a new stases would be reached well after the atmospheric levels of ghg has stabilized.

It will also confirm the accelerated rate of change for impacts such as sea - level rise, the steady retreat of Arctic sea ice and quickened melting of ice sheets and glaciers, as well as offer more detail on scenarios that will shape international negotiations over both short - term and long - term greenhouse gas emissions, including how long «business as usual» can be sustained without dangerous risk.

While sea level has varied greatly in the past, it has generally changed slowly, over many thousands of years — except when ice sheets collapse.

They use a range of techniques to track changes in the volume of the ice - sheet over a 500 - year period, and compare it with measurements of ice - accumulation obtained by deep boring undertaken by Lonnie Thompson of Ohio State University.

Climate change research topics identified for immediate action • Thorough understanding of the physics and dynamics of the Greenland and Antarctic ice sheets, with a view to predicting sea level rise within 20 % for a specified change in climate over the ice sheets.

The remaining slow drift to lower GMT and pCO2 over glacial time, punctuated by higher - frequency variability and the dust − climate feedbacks, may reflect the consequences of the growth of continental ice sheets via albedo increases (also from vegetation changes) and increased CO2 dissolution in the ocean from cooling.

N.b. this diverges from the commonly used «Charney sensitivity» which describes temperature change over the next century or so, and which is less than the change expected over the multi-millenial scale of dwindling ice sheets and vegetation changes.

The mass balance of the ice sheets continues to change over time.

To gain a longer view, Dr Jones and her colleagues used a compilation of records from natural archives such as ice cores from the Antarctic ice sheet, which show how the region's climate has changed over the last 200 years.

However, the accelerated retreat of glaciers, combined with greater melting of these ice sheets, suggest that earlier projections of sea - level rise over the next century — such as in the 2007 report of the Intergovernmental Panel on Climate Change — are conservative.8, 9

Consider, for example, that Lowe, et al. [in Avoiding Dangerous Climate Change, H.J. Schellnhuber et al. (eds), Cambridge University Press, Cambridge, 2006, p. 32 - 33], based on a «pessimistic, but plausible, scenario in which atmospheric carbon dioxide concentrations were stabilised at four times pre-industrial levels,» estimated that a collapse of the Greenland Ice Sheet would over the next 1,000 years raise sea level by 2.3 meters (with a peak rate of 0.5 mm / yr).

It only shows that the huge climate sensitivity over the glacial / interglacial transitions is mainly from ice sheet albedo changes.

``... the most profound contemporary changes to the ice sheets and their contribution to sea level rise can be attributed to ocean thermal forcing that is sustained over decades and may already have triggered a period of unstable glacier retreat.»