scholarly journals Statistical-Dynamical Model of Accumulation on the Greenland Ice Sheet

1984 ◽  
Vol 5 ◽  
pp. 69-74 ◽  
Author(s):  
Richard A. Keen
Keyword(s):  
Moisture Content ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Relative Vorticity ◽  
Ice Age ◽  
Cyclonic Activity ◽  
Atmospheric Moisture ◽  
Distribution Maps ◽  
Southern Half ◽  
Atmospheric Moisture Content

A relatively simple, three-parameter model is used to simulate the annual precipitation (accumulation) distribution for the Greenland ice sheet and surrounding regions. The three parameters are (1) the flux of relative vorticity at the 500 mbar level (a measure of cyclonic activity), (2) atmospheric moisture content, and (3) surface terrain. The climatological (1946–79) precipitation distribution predicted by the model displays major features of the observed distribution derived from pit studies. However, the model suggests that, due to changes in storm tracks during this period of 33 a, accumulation distribution maps based on pit studies for varying periods of record may not be representative of a true mean for a uniform period of record. The model is then applied to reconstructed ice-age conditions. Compared to present conditions, accumulation reductions of 60¾ or more are indicated for much of the southern half of Greenland; only slight reductions are noted for northern Greenland.

scholarly journals Statistical-Dynamical Model of Accumulation on the Greenland Ice Sheet

1984 ◽  
Vol 5 ◽  
pp. 69-74 ◽  
Author(s):  
Richard A. Keen
Keyword(s):  
Moisture Content ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Relative Vorticity ◽  
Ice Age ◽  
Cyclonic Activity ◽  
Atmospheric Moisture ◽  
Distribution Maps ◽  
Southern Half ◽  
Atmospheric Moisture Content

A relatively simple, three-parameter model is used to simulate the annual precipitation (accumulation) distribution for the Greenland ice sheet and surrounding regions. The three parameters are (1) the flux of relative vorticity at the 500 mbar level (a measure of cyclonic activity), (2) atmospheric moisture content, and (3) surface terrain. The climatological (1946–79) precipitation distribution predicted by the model displays major features of the observed distribution derived from pit studies. However, the model suggests that, due to changes in storm tracks during this period of 33 a, accumulation distribution maps based on pit studies for varying periods of record may not be representative of a true mean for a uniform period of record. The model is then applied to reconstructed ice-age conditions. Compared to present conditions, accumulation reductions of 60¾ or more are indicated for much of the southern half of Greenland; only slight reductions are noted for northern Greenland.

scholarly journals Blowing snow in coastal Adélie Land, Antarctica: three atmospheric-moisture issues

2014 ◽  
Vol 8 (5) ◽  
pp. 1905-1919 ◽  
Author(s):  
H. Barral ◽  
C. Genthon ◽  
A. Trouvilliez ◽  
C. Brun ◽  
C. Amory
Keyword(s):  
Moisture Content ◽  
Snow Accumulation ◽  
Blowing Snow ◽  
Atmospheric Moisture ◽  
Atmospheric Models ◽  
Moisture Fluxes ◽  
Measurement Uncertainties ◽  
Strong Winds ◽  
The Impact ◽  
Atmospheric Moisture Content

Abstract. A total of 3 years of blowing-snow observations and associated meteorology along a 7 m mast at site D17 in coastal Adélie Land are presented. The observations are used to address three atmospheric-moisture issues related to the occurrence of blowing snow, a feature which largely affects many regions of Antarctica: (1) blowing-snow sublimation raises the moisture content of the surface atmosphere close to saturation, and atmospheric models and meteorological analyses that do not carry blowing-snow parameterizations are affected by a systematic dry bias; (2) while snowpack modelling with a parameterization of surface-snow erosion by wind can reproduce the variability of snow accumulation and ablation, ignoring the high levels of atmospheric-moisture content associated with blowing snow results in overestimating surface sublimation, affecting the energy budget of the snowpack; (3) the well-known profile method of calculating turbulent moisture fluxes is not applicable when blowing snow occurs, because moisture gradients are weak due to blowing-snow sublimation, and the impact of measurement uncertainties are strongly amplified in the case of strong winds.

scholarly journals Why Does Air Passage over Forest Yield More Rain? Examining the Coupling between Rainfall, Pressure, and Atmospheric Moisture Content*

2014 ◽  
Vol 15 (1) ◽  
pp. 411-426 ◽  
Author(s):  
A. M. Makarieva ◽  
V. G. Gorshkov ◽  
D. Sheil ◽  
A. D. Nobre ◽  
P. Bunyard ◽  
...  
Keyword(s):  
Moisture Content ◽  
Forest Cover ◽  
Meteorological Data ◽  
Circulation Pattern ◽  
Forest Loss ◽  
Amazon Forest ◽  
Atmospheric Moisture ◽  
Wet Season ◽  
Atmospheric Moisture Content ◽  
Rainy Days

Abstract The influence of forest loss on rainfall remains poorly understood. Addressing this challenge, Spracklen et al. recently presented a pantropical study of rainfall and land cover that showed that satellite-derived rainfall measures were positively correlated with the degree to which model-derived air trajectories had been exposed to forest cover. This result confirms the influence of vegetation on regional rainfall patterns suggested in previous studies. However, the conclusion of Spracklen et al.—that differences in rainfall reflect air moisture content resulting from evapotranspiration while the circulation pattern remains unchanged—appears undermined by methodological inconsistencies. Here methodological problems are identified with the underlying analyses and the quantitative estimates for rainfall change predicted if forest cover is lost in the Amazon. Alternative explanations are presented that include the distinct role of forest evapotranspiration in creating low-pressure systems that draw moisture from the oceans to the continental hinterland. A wholly new analysis of meteorological data from three regions in Brazil, including the central Amazon forest, reveals a tendency for rainy days during the wet season with column water vapor (CWV) exceeding 50 mm to have higher pressure than rainless days, while at lower CWV, rainy days tend to have lower pressure than rainless days. The coupling between atmospheric moisture content and circulation dynamics underlines that the danger posed by forest loss is greater than suggested by consideration of moisture recycling alone.

Greenland fjord productivity under climate change - multiproxy late-Holocene records from two contrasting fjord systems

2020 ◽  
Author(s):  
Anna Bang Kvorning ◽  
Tania Beate Thomsen ◽  
Mimmi Oksman ◽  
Marit-Solveig Seidenkrantz ◽  
Christof Pearce ◽  
...  
Keyword(s):  
Climate Change ◽  
Primary Productivity ◽  
Negative Impact ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Age ◽  
Dinoflagellate Cyst ◽  
Coastal Marine ◽  
The Future ◽  
The Impact

<p>The Greenland Ice Sheet has been losing mass at an increasing rate over the past decades due to atmospheric and oceanic warming. As a result, freshwater discharge from the Greenland Ice sheet has doubled in the last two decades and is expected to strongly increase in the future, with a large impact on the functioning of coastal marine ecosystems. While glacier runoff delivers nutrients and labile carbon into the fjords, an increase in sediment inputs is expected to have a negative impact in primary productivity, due to increased turbidity and subsequent reduction in available light for photosynthesis. Bridging modern satellite, historical and paleo-records is a key approach, as our capacity to project future scenarios requires an understanding of long-term dynamics, and insight into past warm(er) climate periods that may serve as analogues for the future. We will present results from a master’s project developed within the framework of project GreenShift: Greenland fjord productivity under climate change. Two high-resolution sediment core records from two contrasting fjord systems in NE and SW Greenland were analysed to assess the impact of Greenland Ice Sheet melt on sediment fluxes and primary productivity, focusing on the time period from the Little Ice Age until present. The overall goal of this work is to gain a better understanding of the possible linkages between GIS melt and productivity in Greenland fjord systems, with a view to improve future projections. We followed a multiproxy approach including grain-size distribution, organic carbon and biogenic silica fluxes; and dinoflagellate cyst analyses. Our preliminary results show an overall trend towards sea-surface freshening in recent decades for both fjords influenced by land-terminating (NE) and marine-terminating (SW) glaciers, alongside with important differences both in terms of sedimentary organic composition and dinoflagellate cyst assemblages.  </p>

scholarly journals Ice-age ice-sheet rheology: constraints from the Last Glacial Maximum form of the Laurentide ice sheet

2000 ◽  
Vol 30 ◽  
pp. 163-176 ◽  
Author(s):  
W. Richard Peltier ◽  
David L. Goldsby ◽  
David L. Kohlstedt ◽  
Lev Tarasov
Keyword(s):  
Last Glacial Maximum ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Glacial Maximum ◽  
Ice Age ◽  
Laurentide Ice Sheet ◽  
Last Glacial ◽  
Flow Law ◽  
The Last Glacial Maximum ◽  
The Last Glacial

AbstractState-of-the-art thermomechanical models of the modern Greenland ice sheet and the ancient Laurentide ice sheet that covered Canada at the Last Glacial Maximum (LGM) are not able to explain simultaneously the observed forms of these cryospheric structures when the same, anisotropy-enhanced, version of the conventional Glen flow law is employed to describe their rheology. The LGM Laurentide ice sheet, predicted to develop in response to orbital climate forcing, is such that the ratio of its thickness to its horizontal extent is extremely large compared to the aspect ratio inferred on the basis of surface-geomorphological and solid-earth-geophysical constraints. We show that if the Glen flow law representation of the rheology is replaced with a new rheology based upon very high quality laboratory measurements of the stress-strain-rate relation then the aspect ratios of both the modern Greenland ice sheet and the Laurentide ice sheet, that existed at the LGM, are simultaneously explained with little or no retuning of the flow law.

scholarly journals Increase in Near-Surface Atmospheric Moisture Content due to Land Use Changes: Evidence from the Observed Dewpoint Temperature Data

2008 ◽  
Vol 136 (4) ◽  
pp. 1554-1561 ◽  
Author(s):  
Rezaul Mahmood ◽  
Kenneth G. Hubbard ◽  
Ronnie D. Leeper ◽  
Stuart A. Foster
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Moisture Content ◽  
Great Plains ◽  
Growing Season ◽  
Atmospheric Moisture ◽  
Near Surface ◽  
Dewpoint Temperature ◽  
Atmospheric Moisture Content

Abstract Land use change can significantly affect root zone soil moisture, surface energy balance, and near-surface atmospheric temperature and moisture content. During the second half of the twentieth century, portions of the North American Great Plains have experienced extensive introduction of irrigated agriculture. It is expected that land use change from natural grass to irrigated land use would significantly increase near-surface atmospheric moisture content. Modeling studies have already shown an enhanced rate of evapotranspiration from the irrigated areas. The present study analyzes observed dewpoint temperature (Td) to assess the affect of irrigated land use on near-surface atmospheric moisture content. This investigation provides a unique opportunity to use long-term (1982–2003) mesoscale Td data from the Automated Weather Data Network of the high plains. Long-term daily Td data from 6 nonirrigated and 11 irrigated locations have been analyzed. Daily time series were developed from the hourly data. The length of time series was the primary factor in selection of these stations. Results suggest increase in growing-season Td over irrigated areas. For example, average growing-season Td due to irrigation can be up to 1.56°C higher relative to nonirrigated land uses. It is also found that Td for individual growing-season month at irrigated locations can be increased up to 2.17°C by irrigation. Based on the results, it is concluded that the land use change in the Great Plains has modified near-surface moistness.

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