Carbon inventory of Siberian Yedoma and thermokarst deposits
1,* 1 1
Jens Strauss , Lutz Schirrmeister , Sebastian Wetterich
1 Alfred Wegener Institute Potsdam, Department of Periglacial Research, Telegrafenberg, 14473 Potsdam, Germany; *contact: Jens.Strauss@awi.de
I. Background
II. Methods
III. Results and Discussion
IV. Conclusion
REFERENCES
100
Kilometers
0
130°E 140°E
72°N
70°N
Buor Khaya Peninsula
Lena
Laptev Sea Arctic Ocean
Kolyma
Lena
Yenissey
Alaska
Green land
Pleistocene Yedoma depositsHolocene Alas deposits
Funded by:
Proxy Method / Device
Radiocarbon ages AMS 14C
Grain size Coulter Laser (LS 200)
Bulk density Archimedes principle and a gas pycnometer (Accu-
Pyc-1330, Micrometrics)
OM characteristics TOC (Vario Max C, Elementar) C/N ratios (Vario El III, Elementar)
Stable water isotopes mass spectrometer (Finnigan MAT Delta-S) Lipid biomarkers (isoprenoid and branched
glycerol dialkyl glycerol tetraether, GDGT)
HPLC (Shimadzu LC10AD)-MS (Finnigan TSQ 7000)
During the late Quaternary, a large pool of organic carbon accumulated in the arctic permafrost zone.
Because of the potential re-introduction into the biogeochemical cycle from degrading permafrost, the organic-matter (OM) inventory of ice-rich permafrost deposits and its degradation features is relevant to current concerns about the effects of global warming.
Our study site is located on the Buor Khaya peninsula (N 71.6°, E 132.2°, Fig. 1), Yakutia (Russia).
The research questions are:
- How much and which type of OM is stored in ice-rich arctic lowlands?
- What are the paleoenvironmental conditions of the source biota?
Fig. 1: Study site Buor Khaya
Fig. 3: Summary of OM and lipid biomarker proxies; Alas profile Buo-01
Fig. 4: Summary of OM and lipid biomarker proxies; Yedoma profile Buo-02
Fig. 5: Summary of OM and lipid biomarker proxies; Yedoma profile Buo-04
Stratigraphically, there are two main types of deposition units at the study site. The first unit is composed of ice-rich permafrost (Yedoma, Fig. 4 and 5). The second unit are thermokarst deposits (Alas, Fig.3) resulting from thermal degradation of Yedoma.
Grain-size (distribution curves and fractions) illustrate that Alas is made up of degraded Yedoma. The bulk density average is ca. 1 10³kg/m³. The TOC content is 2.4 wt% for Yedoma, 10.2 wt% for Alas and low degraded. This illustrates that the deposits accumulated at relatively fast rates and the OM underwent a short time of decomposition before it was incorporated into permafrost. The volumetric OM content of the Yedoma and Alas is 13 ± 11 kg/m³ and 27 ± 18 kg/m³, respectively.
The stable water Isotopes reveal cold temperatures especially for Yedoma. Alas deposits indicate warmer conditions compared to Yedoma, but at the lower part (Fig.
5, Buo-04-C) Yedoma reflects a remarkably warm isotope signal.
After Wejers et al. (2007) it is possible to calculate absolute temperature values using bacterial (branched) GDGT's. Negative values (exception at Buo-02-B, Fig. 4) reveal feasible results for permafrost. An astonishing fact is that Alas reveals the lowest temperatures. We interpret these GDGT temperatures as a growth/summer periods signal. Possibly the Holocene summers have been colder because of a lesser continental climate.
The concentration of archaeol suggests a response of archaeal communities to temperature and humidity changes in the past (Griess et al. 2011). More archeol means larger acheal communities, which is related to a drier and warmer climate (Fig.3).
OM proxies reveal a significant carbon inventory of the studied deposits. Yedoma and Alas contain 13 ± 11 kg/m³ and 27 ± 18 kg/m³, respectively.
Nearly all Biomarker temperature reconstruction reveal negative values This biomarker proxy is a promising tool and could be an ideal supplement to the temperature signals inferred from water isotopes.
Archeol can be employed as a proxy for archeal communities and therefore used as paleoclimatic reconstructions
0 20 40 60 TOC [wt %]
0 50 100 organic carbon
inventory [kg/m³]
0 102030 C/N 0 50 100
grain size fractions
[vol %]
0 25 50 mean grain
size [µm]
-10 0 temperature
[°C]
0 1000 16000 24000
total GDGT [ng/gSediment]
-30-25-20 d18O [‰ vs VSMOW]
0 30000
60000
radiocarbon age [a BP]
7 8 9
altitude[ma.s.l.]
0 0.8 1.6 bulk density [10³kg/m³]
0 100 200 5000 10000
Archeol [ng/gSediment]
Buo-01
3665 ± 35
8140
± 50
0 50 100 organic carbon
inventory [kg/m³]
0 25 50 mean grain
size [µm]
27 28 29 30
0 20 40 60 TOC [wt %]
0 102030 C/N 0 50 100
grain size fractions
[vol %]
-10 0 temperature
[°C]
-30-25-20 d18O [‰ vs VSMOW]
0 30000
60000
radiocarbon age [a BP]
22 23 24 25 26
0 0.8 bulk density [10³kg/m³]
24 25 26 27 28
altitude[ma.s.l.]
23 24 25
0 100 200 5000 10000
Archeol [ng/gSediment]
Buo-02-ABuo-02-DBuo-02-BBuo-02-C
30100
± 300
34650
± 550
41500
± 1500
45000
± 2000
43000
± 1500
Clay Silt Sand
carbon inventory TOC
total GDGT temperature
legend
On-going work focusses on identifying other Biomarkers like alkanes, steranes, hopanes, fatty acids, alcohols and sterols for identifying the TOC sources, quality and vulnerability.
Griess, J., K. Mangelsdorf, A. Gattinger, and D. Wagner (2011), Methanogenic communities within terrestrial Late Pleistocene and Holocene permafrost deposits in the central Lena River Delta, Siberia, 25th International Meeting on Organic Geochemistry (IMOG), Interlaken.
Weijers, J. W. H., S. Schouten, J. C. v. d. Donker, Ellen C. Hopmans, and J. S. S. Damste (2007), Environmental controls on bacterial tetraether membrane lipid distribution in soils, Geochimica et Cosmochimica Acta, 71, pp. 703-713.
0 50 100 organic carbon
inventory [kg/m³]
0 25 50 mean grain
size [µm]
13 14 15 16 17 18 19
7 8 9 10
altitude[ma.s.l.]
0 20 40 60 TOC [wt %]
0 102030 C/N 0 50 100
grain size fractions
[vol %]
-10 0 temperature
[°C]
-30-25-20 d18O [‰ vs VSMOW]
0 30000
60000
radiocarbon age [a BP]
4 5 6 7 8 9 10
0 0.8 1.6 bulk density [10³kg/m³]
0 100 200 5000 10000
Archeol [ng/gSediment]
Buo-04-BBuo-04-CBuo-04-A
49000
± 3000
>48000 infinite
>55000 infinite
>49000 infinite
>55000 infinite
Fig. 2: Yedoma profile Buo-02 (photo taken by F. Günhter)
