scholarly journals Signals of tree volume and temperature in a high-resolution record of pollen accumulation rates in northern Finland

2012 ◽  
Vol 27 (6) ◽  
pp. 564-574 ◽  
Author(s):  
F. Mazier ◽  
A. B. Nielsen ◽  
A. Broström ◽  
S. Sugita ◽  
S. Hicks
Keyword(s):  
High Resolution ◽  
Accumulation Rates ◽  
Pollen Accumulation Rates

scholarly journals Linking modern pollen accumulation rates to biomass: Quantitative vegetation reconstruction in the western Klamath Mountains, NW California, USA

The Holocene ◽  
2021 ◽  
pp. 095968362098803
Author(s):  
Clarke A Knight ◽  
Mark Baskaran ◽  
M Jane Bunting ◽  
Marie Champagne ◽  
Matthew D Potts ◽  
...  
Keyword(s):  
Mean Squared Error ◽  
Plant Biomass ◽  
Source Area ◽  
Pollen Deposition ◽  
Accumulation Rates ◽  
Klamath Mountains ◽  
Plant Abundance ◽  
Circular Area ◽  
Value Analysis ◽  
Pollen Accumulation Rates

Quantitative reconstructions of vegetation abundance from sediment-derived pollen systems provide unique insights into past ecological conditions. Recently, the use of pollen accumulation rates (PAR, grains cm−2 year−1) has shown promise as a bioproxy for plant abundance. However, successfully reconstructing region-specific vegetation dynamics using PAR requires that accurate assessments of pollen deposition processes be quantitatively linked to spatially-explicit measures of plant abundance. Our study addressed these methodological challenges. Modern PAR and vegetation data were obtained from seven lakes in the western Klamath Mountains, California. To determine how to best calibrate our PAR-biomass model, we first calculated the spatial area of vegetation where vegetation composition and patterning is recorded by changes in the pollen signal using two metrics. These metrics were an assemblage-level relevant source area of pollen (aRSAP) derived from extended R-value analysis ( sensu Sugita, 1993) and a taxon-specific relevant source area of pollen (tRSAP) derived from PAR regression ( sensu Jackson, 1990). To the best of our knowledge, aRSAP and tRSAP have not been directly compared. We found that the tRSAP estimated a smaller area for some taxa (e.g. a circular area with a 225 m radius for Pinus) than the aRSAP (a circular area with a 625 m radius). We fit linear models to relate PAR values from modern lake sediments with empirical, distance-weighted estimates of aboveground live biomass (AGLdw) for both the aRSAP and tRSAP distances. In both cases, we found that the PARs of major tree taxa – Pseudotsuga, Pinus, Notholithocarpus, and TCT (Taxodiaceae, Cupressaceae, and Taxaceae families) – were statistically significant and reasonably precise estimators of contemporary AGLdw. However, predictions weighted by the distance defined by aRSAP tended to be more precise. The relative root-mean squared error for the aRSAP biomass estimates was 9% compared to 12% for tRSAP. Our results demonstrate that calibrated PAR-biomass relationships provide a robust method to infer changes in past plant biomass.

scholarly journals A representative density profile of the North Greenland snowpack

2016 ◽  
Vol 10 (5) ◽  
pp. 1991-2002 ◽  
Author(s):  
Christoph Florian Schaller ◽  
Johannes Freitag ◽  
Sepp Kipfstuhl ◽  
Thomas Laepple ◽  
Hans Christian Steen-Larsen ◽  
...  
Keyword(s):  
Remote Sensing ◽  
High Resolution ◽  
Density Profile ◽  
Accumulation Rate ◽  
Sampling Technique ◽  
Data Sets ◽  
Accumulation Rates ◽  
The North ◽  
North Greenland ◽  
Good Agreement

Abstract. Along a traverse through North Greenland in May 2015 we collected snow cores up to 2 m depth and analyzed their density and water isotopic composition. A new sampling technique and an adapted algorithm for comparing data sets from different sites and aligning stratigraphic features are presented. We find good agreement of the density layering in the snowpack over hundreds of kilometers, which allows the construction of a representative density profile. The results are supported by an empirical statistical density model, which is used to generate sets of random profiles and validate the applied methods. Furthermore we are able to calculate annual accumulation rates, align melt layers and observe isotopic temperatures in the area back to 2010. Distinct relations of δ18O with both accumulation rate and density are deduced. Inter alia the depths of the 2012 melt layers and high-resolution densities are provided for applications in remote sensing.

scholarly journals Diatom ooze—A large marine mercury sink

Science ◽  
2018 ◽  
Vol 361 (6404) ◽  
pp. 797-800 ◽  
Author(s):  
Sara Zaferani ◽  
Marta Pérez-Rodríguez ◽  
Harald Biester
Keyword(s):  
High Resolution ◽  
Southern Ocean ◽  
Marine Sediment ◽  
Crucial Role ◽  
Anthropogenic Pollution ◽  
Atmospheric Mercury ◽  
Mercury Accumulation ◽  
Accumulation Rates ◽  
Sediment Data

The role of algae for sequestration of atmospheric mercury in the ocean is largely unknown owing to a lack of marine sediment data. We used high-resolution cores from marine Antarctica to estimate Holocene global mercury accumulation in biogenic siliceous sediments (diatom ooze). Diatom ooze exhibits the highest mercury accumulation rates ever reported for the marine environment and provides a large sink of anthropogenic mercury, surpassing existing model estimates by as much as a factor of 7. Anthropogenic pollution of the Southern Ocean began ~150 years ago, and up to 20% of anthropogenic mercury emitted to the atmosphere may have been stored in diatom ooze. These findings reveal the crucial role of diatoms as a fast vector for mercury sequestration and diatom ooze as a large marine mercury sink.

Revisiting pollen accumulation rates from Swedish lake sediments

The Holocene ◽  
2008 ◽  
Vol 18 (2) ◽  
pp. 293-305 ◽  
Author(s):  
Thomas Giesecke ◽  
Sonia L. Fontana
Keyword(s):  
Lake Sediments ◽  
Accumulation Rates ◽  
Pollen Accumulation Rates

scholarly journals Snow-stratification investigation on an Antarctic ice stream with an X-band radar system

1991 ◽  
Vol 37 (127) ◽  
pp. 323-325 ◽  
Author(s):  
Richard R. Forster ◽  
Curt H. Davis ◽  
Timothy W. Rand ◽  
Richard K. Moore
Keyword(s):  
Remote Sensing ◽  
High Resolution ◽  
Microwave Remote Sensing ◽  
Snow Accumulation ◽  
Radar System ◽  
Accumulation Rates ◽  
X Band ◽  
Local Topography ◽  
Cw Radar ◽  
Insight Into

AbstractAn X-band FM-CW radar was used to determine the feasibility of observing annual snow-accumulation layers in Antarctica with a high-resolution inexpensive radar system. The formation of layering boundaries, their resultant electromagnetic discontinuity and their detection by reflected energy are presented. Large returns from depths corresponding to reasonable positions for annual layers were found. The average accumulation rates calculated from the radar returns agree with those measured in a previous pit study done in the same area. The detection of the annual accumulation layers with this system implies a simple, inexpensive mobile radar could be used to profile large areas allowing the distorting effects of local topography to be removed.This type of system with a concurrent pit study could provide insight into the effect of sub-surface strata on spaceborne or airborne microwave remote sensing.

scholarly journals Combined Magnetostratigraphy From Three Localities of the Rainstorm Member of the Johnnie Formation in California and Nevada, United States Calibrated by Cyclostratigraphy: A 13 R/Ma Reversal Frequency for the Ediacaran

2021 ◽  
Vol 9 ◽  
Author(s):  
Kenneth P. Kodama
Keyword(s):  
United States ◽  
High Resolution ◽  
Accumulation Rate ◽  
Sediment Accumulation ◽  
Critical Time ◽  
Sediment Accumulation Rate ◽  
Accumulation Rates ◽  
Field Reversal ◽  
South Central ◽  
Reversal Frequency

A combined magnetostratigraphy for the Rainstorm Member of the Ediacaran Johnnie Formation was constructed using the sediment accumulation rates determined by rock magnetic cyclostratigraphy for three localities of the Rainstorm Member to provide a high resolution, time-calibrated record of geomagnetic field reversal frequency at a critical time period in Earth history. Two previously reported magnetostratigraphy records from Death Valley, California, the Nopah Range and Winters Pass Hills (Minguez et al., 2015), were combined with new paleomagnetic and cyclostratigraphic results from the Desert Range locality of the Rainstorm Member in south central Nevada, United States . The Johnnie oolite marker bed is at the base of each of the three sections and allows their regional correlation. The Nopah Range and Desert Range localities have similar sediment accumulation rates of ∼5 cm/ka, so their stratigraphic sections can be combined directly. The Winters Pass Hills locality has a higher sediment accumulation rate of 8.4 cm/ka, therefore its stratigraphic positions are multiplied by 0.6 to combine with the Desert Range and Nopah Range magnetostratigraphy. The thermal demagnetization results from the Desert Range locality isolates characteristic remanent magnetizations that indicate two nearly antipodal east-west and shallow directions and a mean paleopole (11.7˚N, 348.4˚E) that is consistent with “shallow” Ediacaran directions. The Desert Range also yields a magnetic susceptibility rock magnetic cyclostratigraphy that records short eccentricity, obliquity, and precession astronomically-forced climate cycles in the Ediacaran. The high-resolution combined magnetostratigraphy with nearly meter-scale stratigraphic spacing (nominally 23 ka, based on the Desert Range sediment accumulation rate), indicates 11 polarity intervals in a cyclostratigraphy-calibrated duration of 849 ka, indicating a reversal frequency of 13 R/Ma. The Rainstorm Member records the Shuram carbon isotope excursion, hence its age is ∼574 Ma. Given the recent cyclostratigraphy-calibrated reversal frequency of 20 R/Ma from the Zigan Formation (Levashova et al., 2021) at 547 Ma, our results show that reversal frequency was high but fluctuated during the Ediacaran.

Sign in / Sign up

Export Citation Format

Share Document