| 21. |
- Büntgen, Ulf, et al.
(author)
-
Reply to 'Limited Late Antique cooling'
- 2017
-
In: Nature Geoscience. - : Springer Science and Business Media LLC. - 1752-0894 .- 1752-0908. ; 10:4, s. 243-243
-
Journal article (other academic/artistic)
|
|
| 22. |
- Catalan, Nuria, et al.
(author)
-
Organic carbon decomposition rates controlled by water retention time across inland waters
- 2016
-
In: Nature Geoscience. - 1752-0894 .- 1752-0908. ; 9:7, s. 501-504
-
Journal article (peer-reviewed)abstract
- The loss of organic carbon during passage through the continuum of inland waters from soils to the sea is a critical component of the global carbon cycle(1-3). Yet, the amount of organic carbon mineralized and released to the atmosphere during its transport remains an open question(2,4-6), hampered by the absence of a common predictor of organic carbon decay rates(1,7). Here we analyse a compilation of existing field and laboratory measurements of organic carbon decay rates and water residence times across a wide range of aquatic ecosystems and climates. We find a negative relationship between the rate of organic carbon decay and water retention time across systems, entailing a decrease in organic carbon reactivity along the continuum of inland waters. We find that the half-life of organic carbon is short in inland waters (2.5 +/- 4.7 yr) compared to terrestrial soils and marine ecosystems, highlighting that freshwaters are hotspots of organic carbon degradation. Finally, we evaluate the response of organic carbon decay rates to projected changes in runoff(8). We calculate that regions projected to become drier or wetter as the global climate warms will experience changes in organic carbon decay rates of up to about 10%, which illustrates the influence of hydrological variability on the inland waters carbon cycle.
|
|
| 23. |
- Christensen, Torben
(author)
-
Climate Science Patchy Peat
- 2009
-
In: Nature Geoscience. - : Springer Science and Business Media LLC. - 1752-0908 .- 1752-0894. ; 2:3, s. 163-164
-
Journal article (other academic/artistic)
|
|
| 24. |
- Christensen, Torben R.
(author)
-
Permafrost : It's a gas
- 2016
-
In: Nature Geoscience. - : Springer Science and Business Media LLC. - 1752-0894 .- 1752-0908. ; 9:9, s. 647-648
-
Journal article (peer-reviewed)
|
|
| 25. |
- Conley, Daniel, et al.
(author)
-
Silica cycling over geologic time
- 2015
-
In: Nature Geoscience. - : Springer Science and Business Media LLC. - 1752-0908 .- 1752-0894. ; 8:6, s. 431-432
-
Journal article (other academic/artistic)
|
|
| 26. |
- Coxall, Helen K., et al.
(author)
-
Export of nutrient rich Northern Component Water preceded early Oligocene Antarctic glaciation
- 2018
-
In: Nature Geoscience. - : Springer Science and Business Media LLC. - 1752-0894 .- 1752-0908. ; 11:3, s. 190-196
-
Journal article (peer-reviewed)abstract
- The onset of the North Atlantic Deep Water formation is thought to have coincided with Antarctic ice-sheet growth about 34 million years ago (Ma). However, this timing is debated, in part due to questions over the geochemical signature of the ancient Northern Component Water (NCW) formed in the deep North Atlantic. Here we present detailed geochemical records from North Atlantic sediment cores located close to sites of deep-water formation. We find that prior to 36 Ma, the northwestern Atlantic was stratified, with nutrient-rich, low-salinity bottom waters. This restricted basin transitioned into a conduit for NCW that began flowing southwards approximately one million years before the initial Antarctic glaciation. The probable trigger was tectonic adjustments in subarctic seas that enabled an increased exchange across the Greenland-Scotland Ridge. The increasing surface salinity and density strengthened the production of NCW. The late Eocene deep-water mass differed in its carbon isotopic signature from modern values as a result of the leakage of fossil carbon from the Arctic Ocean. Export of this nutrient-laden water provided a transient pulse of CO2 to the Earth system, which perhaps caused short-term warming, whereas the long-term effect of enhanced NCW formation was a greater northward heat transport that cooled Antarctica.
|
|
| 27. |
- Cronin, T. M., et al.
(author)
-
Deep Arctic Ocean warming during the last glacial cycle
- 2012
-
In: Nature Geoscience. - 1752-0894 .- 1752-0908. ; 5:9, s. 631-634
-
Journal article (peer-reviewed)abstract
- In the Arctic Ocean, the cold and relatively fresh water beneath the sea ice is separated from the underlying warmer and saltier Atlantic Layer by a halocline. Ongoing sea ice loss and warming in the Arctic Ocean(1-7) have demonstrated the instability of the halocline, with implications for further sea ice loss. The stability of the halocline through past climate variations(8-10) is unclear. Here we estimate intermediate water temperatures over the past 50,000 years from the Mg/Ca and Sr/Ca values of ostracods from 31 Arctic sediment cores. From about 50 to 11 kyr ago, the central Arctic Basin from 1,000 to 2,500 m was occupied by a water mass we call Glacial Arctic Intermediate Water. This water mass was 1-2 degrees C warmer than modern Arctic Intermediate Water, with temperatures peaking during or just before millennial-scale Heinrich cold events and the Younger Dryas cold interval. We use numerical modelling to show that the intermediate depth warming could result from the expected decrease in the flux of fresh water to the Arctic Ocean during glacial conditions, which would cause the halocline to deepen and push the warm Atlantic Layer into intermediate depths. Although not modelled, the reduced formation of cold, deep waters due to the exposure of the Arctic continental shelf could also contribute to the intermediate depth warming.
|
|
| 28. |
- Datry, T., et al.
(author)
-
A global analysis of terrestrial plant litter dynamics in non-perennial waterways
- 2018
-
In: Nature Geoscience. - : Nature Publishing Group. - 1752-0894 .- 1752-0908. ; 11:7, s. 497-503
-
Journal article (peer-reviewed)abstract
- Perennial rivers and streams make a disproportionate contribution to global carbon (C) cycling. However, the contribution of intermittent rivers and ephemeral streams (IRES), which sometimes cease to flow and can dry completely, is largely ignored although they represent over half the global river network. Substantial amounts of terrestrial plant litter (TPL) accumulate in dry riverbeds and, upon rewetting, this material can undergo rapid microbial processing. We present the results of a global research collaboration that collected and analysed TPL from 212 dry riverbeds across major environmental gradients and climate zones. We assessed litter decomposability by quantifying the litter carbon-to-nitrogen ratio and oxygen (O2) consumption in standardized assays and estimated the potential short-term CO2 emissions during rewetting events. Aridity, cover of riparian vegetation, channel width and dry-phase duration explained most variability in the quantity and decomposability of plant litter in IRES. Our estimates indicate that a single pulse of CO2 emission upon litter rewetting contributes up to 10% of the daily CO2 emission from perennial rivers and stream, particularly in temperate climates. This indicates that the contributions of IRES should be included in global C-cycling assessments.
|
|
| 29. |
- de Lavergne, Casimir, et al.
(author)
-
Getting to the bottom of the ocean
- 2016
-
In: Nature Geoscience. - : Springer Science and Business Media LLC. - 1752-0894 .- 1752-0908. ; 9:12, s. 857-858
-
Journal article (other academic/artistic)
|
|
| 30. |
- Ding, Jinzhi, et al.
(author)
-
Decadal soil carbon accumulation across Tibetan permafrost regions
- 2017
-
In: Nature Geoscience. - 1752-0894 .- 1752-0908. ; 10:6, s. 420-424
-
Journal article (peer-reviewed)abstract
- Permafrost soils store large amounts of carbon. Warming can result in carbon release from thawing permafrost, but it can also lead to enhanced primary production, which can increase soil carbon stocks. The balance of these fluxes determines the nature of the permafrost feedback to warming. Here we assessed decadal changes in soil organic carbon stocks in the active layer-the uppermost 30 cm-of permafrost soils across Tibetan alpine regions, based on repeated soil carbon measurements in the early 2000s and 2010s at the same sites. We observed an overall accumulation of soil organic carbon irrespective of vegetation type, with a mean rate of 28.0 g Cm-2 yr(-1) across Tibetan permafrost regions. This soil organic carbon accrual occurred only in the subsurface soil, between depths of 10 and 30 cm, mainly induced by an increase of soil organic carbon concentrations. We conclude that the upper active layer of Tibetan alpine permafrost currently represents a substantial regional soil carbon sink in a warming climate, implying that carbon losses of deeper and older permafrost carbon might be offset by increases in upper-active-layer soil organic carbon stocks, which probably results from enhanced vegetation growth.
|
|
