Justine Ramage Anne Morgenstern Gustaf Hugelius Daniel Fortier Hugues Lantuit

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Justine Ramage Anne Morgenstern Gustaf Hugelius Daniel Fortier Hugues Lantuit

14.12.2017 Arctic Change 2017

Snapshot of Carbon Distribution and

Degradation in Arctic Valleys

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Soil organic carbon storage in northern

permafrost region:

999 Pg (0-3 m)

Carbon stocks in the Arctic

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Hugelius, G., Strauss, J., Zubrzycki, S., Harden, J. W., Schuur, E., Ping, C. L., ... & O'Donnell, J. A. (2014).

Estimated stocks of circumpolar permafrost carbon with quantified uncertainty ranges and identified data gaps.

Biogeosciences, 11(23), 6573-6593.

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?

Justine Ramage

Hugelius, G., Strauss, J., Zubrzycki, S., Harden, J. W., Schuur, E., Ping, C. L., ... & O'Donnell, J. A. (2014).

Estimated stocks of circumpolar permafrost carbon with quantified uncertainty ranges and identified data gaps.

Biogeosciences, 11(23), 6573-6593.

Soil organic carbon storage in northern

permafrost region:

999 Pg (0-3 m)

Carbon stocks in

the Arctic

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Hillslope processes

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Erosion

Accumulation

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Hillslope processes

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•  Thermal perturbation

•  Localized disturbances: solifluction, active layer detachments, thaw slumps

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Erosion

Accumulation

Hillslope processes

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The two landscape characteristics considered most important for estimating regional coverage of wetland thermokarst landscapes are histel soil coverage and topographic ruggedness (Table 1). We consider histels to be largely susceptible to the development of wetland thermokarst landforms due to their high-ground ice content³⁰. Because histels have high-ground ice content, we did not further use landscape information on ground ice content by itself for estimating regional coverage (Table 1). Wetland thermokarst landscapes can dominate flat landscapes with extensive histels but are assumed to be largely confined to topographic lows in regions with more topographic ruggedness, including valley bottoms and adjacent to ponds and lakes4,5,15,30–33.

Secondary influences on regional coverage include permafrost zonation and sedimentary overburden thickness (Table 1). All else equal, we consider wetland thermokarst landscapes to have lower regional coverage in regions with thin sedimentary overburden and in colder permafrost zones. Thin sedimentary

overburden is considered to limit the potential for vertical land subsidence and thus the development of characteristic thermokarst landforms. In colder permafrost zones, histels often occur in polygonal peatlands characterized by relatively thin organic soils¹ and abundant ice wedges. In such polygonal peatlands it is more likely that thermokarst leads to the development of thermokarst troughs and pits develop⁵, which we consider characteristic of lake thermokarst landscapes (see below). In the non-continuous permafrost zones, our model allows wetland thermokarst landscape coverage to be greater than the permafrost coverage.

This follows our definition of thermokarst landscapes, which includes both permafrost areas susceptible to future thermokarst development and non-permafrost areas of current thermokarst landforms^23,31.

The resulting maps show ‘Very High’ wetland thermokarst landscape coverage in well-known and extensive boreal peatland regions such as the West Siberian Lowlands, the Hudson Bay

High Moder ate

Low

None Very high

Thermokarst landscape coverage

b

Wetland Lake Hillslope

a

c

Figure 2 | Distribution and regional coverage of thermokarst landscapes in the northern boreal and tundra circumpolar permafrost region.

Differentiation is made for (a) wetland (green shading), (b) lake (blue shading) and (c) hillslope thermokarst landscapes (red shading). Coverage is classified as ‘Very High’ (60–100% regional coverage), ‘High’ (30–60%), ‘Moderate’ (10–30%), ‘Low’ (1–10%) and ‘None’ (0–1%). Hillslope thermokarst landscapes are assumed to not reach ‘Very High’ regional coverage. Yellow star symbols indicate study sites, described in literature, of thermokarst landforms characteristic of each thermokarst landscape (Supplementary Table 4-6). Background map of topography is based on GTOPO30 data (USGS, EROS, ESRI), accessed through ArcGIS 9.3.1.

ARTICLE

NATURE COMMUNICATIONS | DOI: 10.1038/ncomms13043

4 NATURE COMMUNICATIONS| 7:13043 | DOI: 10.1038/ncomms13043 | www.nature.com/naturecommunications Olefeldt, D., Goswami, S., Grosse, G., Hayes, D., Hugelius, G., Kuhry, P., ... & Turetsky, M. R. (2016).

Circumpolar distribution and carbon storage of thermokarst landscapes. Nature communications, 7.

4.9%

of the northern circumpolar

permafrost region

6.2%

of SOC storage

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Hillslope thermokarst

terrains

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Research Question

WHAT IS THE IMPACT OF HILLSLOPE PROCESSES ON CARBON STORAGE IN VALLEYS?

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Study Area

±

0 4

Kilometers

Beaufort Sea Beaufort Sea

Slump-D Creek

Fox Creek

Ice Creek

Herschel Island

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Origin and Geomorphology

Watershed: 140 ha 77.5 ha 61.8 ha

Stream length: 2.5 km 1.4 km 0.9 km

Elevation: 81 to 5 m 68 to 4 m 55 to 5 m

Ice Creek West Fox Creek Slump-D Creek

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±

0 4

Kilometers

Beaufort Sea Herschel Island

!

! !

!

!! !! !

!!

! !

!

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!

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!!!

!!

!

! !

! ! !

!

±

± ±

0 300 m

0 300 m 0 300 m

Legend

Ice Creek Gullies

Streams

! Sampling sites

Bottoms Slopes Uplands Fox Creek

Slump-D Creek

±

0 4

Kilometers

Beaufort Sea Herschel Island

!

! !

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!!!

!!

!

! !

! ! !

!

±

± ±

0 300 m

0 300 m 0 300 m

Legend

Ice Creek Gullies

Streams

! Sampling sites

Slump-D Creek

±

0 4

Kilometers

Beaufort Sea

Herschel Island

!

!! !! !

!!

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!!!

!!

!

! !

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!

±

± ±

0 300 m

0 300 m 0 300 m

Legend

Ice Creek Gullies

Streams

! Sampling sites

Slump-D Creek

±

0 4

Kilometers

Beaufort Sea

Herschel Island

!

! !

!

!! !! !

!!

! !

!

! !

!

! !

!!!

!!

!

! !

! ! !

!

±

± ±

0 300 m

0 300 m 0 300 m

Legend

Ice Creek Gullies

Streams

! Sampling sites

Slump-D Creek

±

0 4

Kilometers

Beaufort Sea

Herschel Island

!

!! ! ! !

!!

! !

!

! !

!

! !

!!!

!!

!

! !

! ! !

!

±

± ±

0 300 m

0 300 m 0 300 m

Legend

Ice Creek Gullies

Streams

! Sampling sites

Slump-D Creek

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Soil pits: active layer &

permafrost

Sampling Scheme

Upland Herschel

“Undisturbed”

Bottom Guillemot

“Accumulation, wet”

Upstream

Downstream

Erosion Accumulation

Erosion

Accumulation

Erosion Transect 1

Transect 3 Transect 2

Mid-Slope Plover-Jaeger

“Mass wasting” Foot-Slope Plover-Jaeger

“Deposition”

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Slopes

Mid

Bottom

Foot Transect 1

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Sampling Scheme

Upland Herschel

“Undisturbed”

Upstream

Downstream

Erosion

Accumulation

Erosion Transect 1

“Deposition”

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Soil pits: active layer &

permafrost

Upland

Slopes

Mid

Bottom

Foot Transect 1

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Transect 1: Upper valley Sampling

Scheme

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Transects

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Transect 2: Middle valley Sampling

Scheme

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Transects

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Transect 3: Lower valley Sampling

Scheme

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Transects

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Sampling Scheme

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Soil pits: active layer &

permafrost

Upland Herschel

“Undisturbed”

Upstream

Downstream

Erosion

Accumulation

Erosion Transect 1

“Deposition”

Upland

Slopes

Mid

Bottom

Foot Transect 1

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Sampling Scheme

3 valleys 45 sites

316 samples

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Soil pits: active layer &

permafrost

Upland Herschel

“Undisturbed”

Upstream

Downstream

Erosion

Accumulation

Erosion Transect 1

“Deposition”

Upland

Slopes

Mid

Bottom

Foot Transect 1

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Sampling Scheme

3 valleys 45 sites

316 samples

Analyses:

%C

%N

%TOC

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Soil pits: active layer &

permafrost

Upland Herschel

“Undisturbed”

Upstream

Downstream

Erosion

Accumulation

Erosion Transect 1

“Deposition”

Upland

Slopes

Mid

Bottom

Foot Transect 1

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Carbon distribution and degradation

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TNTN

Variables

SOC

TN

C:N

Valley

position

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Carbon distribution and degradation

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Spatial parameters

Results

TNTN

Variables

SOC

TN

C:N

Valley position

Slope orientation Hillslope

position

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ALD mean SOC mean TN mean

C:N mean (cm) (kg C m²) (kg N m²)

Bottom 41.2 ± 9.3 33.8 ± 9.1 2.5 ± 0.8 14.1 ± 2.1 Footslope 94.5 ± 11.0 18.5 ± 6.3 1.9 ± 0.7 11.0 ± 1.5 Midslope 57.6 ± 17.7 25.3 ± 10.4 2.2 ± 0.6 11.8 ± 1.5 Upland 41.1 ± 8.8 27.1 ± 6.3 2.1 ± 0.4 13.9 ± 2.2

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** p < 0.05

Results Carbon distribution

and degradation

Hillslope

position

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_{ALD mean} _{TOC mean} _{TN mean}

C:N mean (cm) (kg C m²) (kg N m²)

Downstream 58.5±22.6 25.1±10.3 2.1±0.7 12.5±2.5 Mid-stream 51.6±19.7 26.3±8.8 2.2±0.5 12.6±1.9 Upstream 38.7±6.0 30.2±4.0 2.2±0.3 14.9±1.6

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** p < 0.05

Results Carbon distribution

and degradation

Valley

position

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_{SOC mean} _{TN mean} _{C:N mean}

kg m² kg m²

East 30.6 ± 6.7 2.3 ± 0.6 14.3 ± 0.7

West 26.7 ± 3.3 2.1 ± 0.2 13.5 ± 0.2

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** p < 0.05

Results Carbon distribution

and degradation

Slope

orientation

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14.12.2017 Arctic Change 2017 Summary

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C:N ratios

Degradation downstream Degradation downhill

++

+

-

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++

+++

Summary

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C:N ratios

Degradation downslope Degradation downhill

++

+

- ++ ++

+

-

+++

SOC and TN stocks

Spatial heterogeneity

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Summary

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Acknowledgments

B ^IG ^THANK ^TO ^MY

COLLEAGUES WHO

HELPED ME DIG ALL SOIL PROFILES

MANUALLY IN 2015!

Jan Kahl Samuel Stettner

George Tanski Anna Irrgang Hugues Lantuit Gustaf Huguelius

Saskia Ruttor Isabel Eischeid

Justine Ramage Anne Morgenstern Gustaf Hugelius Daniel Fortier Hugues Lantuit