Predicting the Loss of Organic Archaeological Deposits at A

Supplementary information: Predicting the loss of organic archaeological deposits at a regional scale in Greenland Jørgen Hollesen1,2, Henning Matthiesen1, Rasmus Fenger-Nielsen1,2, Jakob Abermann3,4, Andreas Westergaard-Nielsen2 & Bo Elberling2

1 Environmental Archaeology and Materials Science, The National Museum of Denmark, IC Modewegsvej, Brede, DK- 2800 Lyngby, Denmark 2 Center for Permafrost (CENPERM), Department of Geosciences and Natural Resource Management (IGN), University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark 3Asiaq, Greenland Survey, Postbox 1003, GL-3900 Nuuk, Greenland 4 Department of Geography and Regional Science, Graz University, Heinrichstraße 36, 8010 Graz, Austria 100 90

space 80

70 pore 60

filled 50

40 water 30

% of % 20 10 0 01-06-2017 01-07-2017 31-07-2017 Kangeq Ersaa Qoornoq Iffiartarfik Sandnes

Supplementary Fig. S1: Percentage of water filled pore space in 0.1 m depth at the five study sites during the summer 2017. The percentage of water filled pore space is the ratio of volumetric soil water content to total soil porosity.

1500

)

C o ( 1000

500 Sum of TDD ofSum

0 Kangeq Ersaa Qoornoq Iffiartarfik Sandnes

Supplementary Fig. S2: Mean annual sum of TDD for the period 2001–2017 derived from the MODIS-based land surface temperature product MOD11A1 V6 (black squares) and observed at the study sites from 1 September 2016–31 August 2017 (blue circles). Vertical bars show ± 1 s.d. 100 a 80 60 40

20 Porosity (vol. (vol. %) Porosity 0 50 b 40 30 20

LOI WT%/Dw LOI 10 0

1000

) 3 - c 800

kg kg m 600 400 200

Bulk density ( density Bulk 0 Kangeq Ersaa Qoornoq Iffiartarfik Sandnes V35 V53d (n=4) (n=2) (n=3) (n=2) (n=3) (n=3) (n=5)

Supplementary Fig. S3: Observed mean values of porosity (a), organic content (b) and bulk density (c). Vertical bars show ± 1 s.d. Thermal conductivity (W m-1 K-1) Heat capacity (MJ m-3 K-1) 0 0.2 0.4 0.6 0.8 0 1 2 3 0 0

Kangeq -50 -50 Erssa

Qoornoq Depth Depth (cm) -100 Depth (cm) -100 Iffiartarfik Sandnes

-150 -150

0.8 3 )

1 y = 0.028x + 0.68

- y = 0.0063x + 0.143

)

K 1

- r² = 0.6763

1 r² = 0.7032

- K

0.6 3 - 2

0.4 (MJm

0.2

capacity Heat Heat 0 0 Thermal conductivity Thermalconductivity (W m 0 20 40 60 80 0 20 40 60 80 Water content (Vol. %) Water content (Vol. %)

Supplementary Fig. S4: Upper: observed depth-specific values of thermal conductivity (left) and heat capacity (right). Lower: Linear regression between observed ground water contents and values of thermal conductivity (left) and heat capacity (right). 0.05

0.04

day 1

- 0.03 g g dw

2 0.02

O mg mg 0.01

Ersaa (-30 cm) (-30 Ersaa Ersaa (-20 cm) Ersaa

Kangeq (-30 cm (-30 Kangeq

Kangeq (-20 cm) (-20 Kangeq cm) (-40 Kangeq cm) (-50 Kangeq

Iffiartarfik (-20 cm (-20 Iffiartarfik

Qoornoq (-10 cm) Qoornoq (-20 cm) Qoornoq (-30 cm) Qoornoq (-40 cm) Qoornoq (-50 cm) Qoornoq

Sandnes (-20 cm) (-20 Sandnes cm) (-40 Sandnes cm) (-60 Sandnes

Iffiartarfik (-10 cm) Iffiartarfik (-30 cm) Iffiartarfik

Supplementary Fig. S5: Observed oxygen consumption rates in 17 different samples at 5 °C. Vertical bars show ± 1 s.d. (n =3).

10 0.1 m depth 10 0.4 m depth

) C o 5 5

0 0

-5 -5 Temperature ( Temperature

-10 -10 01-01-2015 01-01-2016 01-01-2017 01-01-2015 01-01-2016 01-01-2017

10 0.2 m depth 10

) 0.6 m depth

C o 5 5

0 0

Temperature ( Temperature -5 -5

-10 -10 01-01-2015 01-01-2016 01-01-2017 01-01-2015 01-01-2016 01-01-2017

Supplementary Fig. S6: Simulated (red) and measured (black) ground temperatures at the archaeological site Kangeq from 1st January 2015–31st August 2017. 0.1 m depth 0.3 m depth 100 100 80 80

(Vol. (Vol. %) 60 60

40 40 water

20 20 Soil 0 0 01-01-2015 01-01-2016 01-01-2017 01-01-2015 01-01-2016 01-01-2017

100 0.2 m depth 100 0.4 m depth 80 80

(Vol. %) (Vol. 60 60

40 40 water

20 20 Soil 0 0 01-01-2015 01-01-2016 01-01-2017 01-01-2015 01-01-2016 01-01-2017

Supplementary Fig. S7: Simulated (blue) and measured (black) soil water contents in the archaeological deposits at the site Kangeq from 1st January 2015–31st August 2017. The low water content during the winter periods is due to soil frost. Ersaa

Qoornoq Iffiartarfik Sandnes )

C 0.1 m depth 0.1 m depth 0.1 m depth 0.1 m depth

o 10

Temperature ( Temperature -5

-10

) 10 0.2 m depth 0.2 m depth 0.2 m depth 0.2 m depth

C o 5 No data 0

-5 Temperature ( Temperature

-10 )

C 10

o 0.4 m depth 0.4 m depth 0.4 m depth 0.4 m depth

Temperature ( Temperature -5

-10 1/6 1/7 1/8 1/6 1/7 1/8 1/9 1/6 1/7 1/8 1/6 1/7 1/8 1/9

Supplementary Fig. S8 Simulated (red) and measured (black) soil temperatures at the archaeological sites Ersaa, Qoornoq, Iffiartarfik and Sandnes during the summer period 2017. 80 Kangeq 2015 70 y = 0.951x + 4.1775 Kangeq 2016 60 R² = 0.8673 Kangeq 2017 Ersaa 50 Qoornoq 40 Iffiartarfik Sandnes 30

10 Simulated soil water content (Vol. %) water soil (Vol. contentSimulated 0 0 10 20 30 40 50 60 70 80 Observed soil water content (Vol. %)

Supplementary Fig. S9: Linear regression between mean simulated and mean observed ground water contents for the frost free summer period. Vertical and horizontal bars show ± s.d. Ersaa Qoornoq Iffiartarfik Sandnes

100 0.1 m depth 0.1 m depth 0.1 m depth 0.1 m depth 80 60 40 20 0

100 0.2 m depth 0.2 m depth 0.2 m depth 0.2 m depth 80 60 40 20 soil water content (Vol. %) (Vol. soil content water 0

100 0.4 m depth 0.4 m depth 0.4 m depth 0.4 m depth 80 60 40 20 0 1/6 1/7 1/8 1/6 1/7 1/8 1/9 1/6 1/7 1/8 1/6 1/7 1/8 1/9

Supplementary Fig. S10: Simulated (blue) and measured (black) soil water contents at the archaeological sites Ersaa, Qoornoq, Iffiartarfik and Sandnes during the summer period 2017. 20 Kangeq 20 Iffiartarfik 10 10

0 0 -30 -20 -10 0 10 20 -30 -20 -10 0 10 20

-10 -10 Ta Modis Ta y = 1.297x - 1.1094 TaModis -20 R² = 0.8111 -20 y = 1.0961x - 1.9515 -30 -30 R² = 0.8757 Ta Observed Ta Observed

20 20 Ersaa Sandnes 10 10

0 0 -30 -20 -10 0 10 20 -30 -20 -10 0 10 20

-10 -10 Ta Modis Ta y = 1.0114x - 0.7815 Modis Ta y = 0.9825x - 1.3438 -20 R² = 0.8383 -20 R² = 0.8751 -30 -30 Ta Observed Ta Observed

20 Qoornoq

0 -30 -20 -10 0 10 20 -10

Ta Modis Ta y = 1.1148x - 1.2555 -20 R² = 0.8582

-30 Ta Observed

Supplementary Fig. S11: Linear regression between observed air temperatures (Ta) and air temperatures derived from MODIS-based land surface temperature product MOD11A1 V6 that was gap-filled with data from MAR3.7. 60 14 Kangeq Iffiartarfik 50 12 y = 0.7225x + 0.1984 y = 1.0412x + 0.4155 10 r² = 0.7284 40 r² = 0.6675 8 30 6 20 4

10 2 Rain Rain observed Nuuk(mm) 0 Rain observed Kapssillit (mm) 0 0 10 20 30 40 0 5 10 15 20 Rain observed on-site (mm) Rain observed on-site (mm)

14 25 Qoornoq Sandnes 12 y = 0.4973x + 0.2675 20 y = 0.8631x + 0.1142 10 r² = 0.5747 r² = 0.757

8 15

6 10 4 5

Rain Rain observed Nuuk(mm) Rain observed Kapisillit observed Rain Kapisillit (mm) 0 0 0 5 10 15 20 0 5 10 15 20 Rain observed on-site (mm) Rain observed on-site (mm)

Supplementary Fig. S12: Linear regression between precipitation rates observed at the study sites in the frost-free period from 1st September 2016–31st July 2017 and daily precipitation sums from official meteorological stations in Nuuk and Kapisillit. Kangeq and Qoornoq correlated best with data from Nuuk and Iffiartarfik and Sandnes with data from Kapisillit. 1.4 Kobbefjord 1.2 Observed Kobbefjord 1

(m) Modelled

0.8 depth

0.6 Snow 0.4

0.2

2012-01-01 2013-01-01 2014-01-01 2015-01-01 2016-01-01 2017-01-01

Supplementary Fig. S13: Simulated vs observed snow depths for the Nuuk Basic research station located in Kobbefjorden. 2.0

(m) 1.5 Kangeq

depth Ersaa Qoornoq 1.0 Snow Iffiartrafik Sandnes Kobbefjord 0.5

0.0

2012-01-01 2013-01-01 2014-01-01 2015-01-01 2016-01-01 2017-01-01

Date

Supplementary Fig. S14: Modelled snow cover for the five study sites and the Nuuk Basic research station i Kobbefjord. Supplementary Table S1: Study site informations. Samples were taken from the cultural phases highlighted in bold.

Site Latitude Longitude Cultural phases

Kangeq 64°06.433' N 52° 03.104' W Saqqaq, Thule

Ersaa 64°14.796' N 51° 36.449' W Thule

Qoornoq 64°32.027' N 51°05.144' W Thule

Iffiartarfik 64°27.567' N 50°38.738' W Norse, Thule

Kilaarsarfik 64°14.604' N 50° 10.510' W Saqqaq, Dorset, Norse (Sandnes) V35 (Tummeralik) 64°17.196' N 50° 09.136' W Norse

V53D 64°13.603' N 49° 49.157' W Norse o Supplementary Table S2: The Q10 values obtained from O2 consumption measurements at 1, 5, 10 and 15 C.

Site Depth Q10 (1-15 oC) r2 (n=4)

Kangeq 20 2.6 0.99 Kangeq 30 2.3 0.97 Kangeq 40 2.2 0.92 Kangeq 50 2.1 0.96 Erssa 10 2.7 0.98 Erssa 20 2.3 0.95 Qoornoq 10 2.5 0.96 Qoornoq 20 2.3 0.93 Qoornoq 30 2.5 0.95 Qoornoq 40 2.1 0.93 Qoornoq 50 2.6 0.89 Iffiartarfik 10 2.0 0.99 Iffiartarfik 20 1.5 0.79 Iffiartarfik 30 1.7 0.99 Sandnes 20 1.7 0.69 Sandnes 40 2.4 0.95 Sandnes 60 2.5 0.97 Supplementary Table S3: Statistics on the agreement between observed (x) and simulated soil temperatures (y) for the calibration and test simulations.

Calibration (Kangeq) Calibration (Kangeq) 1 January 2015–31 August 2017 1 June–31 August 2015,2016 and 2017 Depth (m) N r2 Regression lines Average N r2 Regression lines Average (y-x) (y-x) 0.1 974 0.86 y=0.99x-0.29 -0.29 276 0.74 y=0.95x+0.52 0.35 0.2 974 0.85 y=0.87x-0.15 -0.11 276 0.85 y=0.97x+0.01 0.01 0.4 974 0.78 y=0.99x-0.14 -0.13 276 0.90 y=1.26x-0.01 0.17 0.6 974 0.55 y=0.96x-0.13 -0.12 276 0.82 y=1.57x-0.03 -0.03

Test 1 (Ersaa) Test 2 (Qoornoq) 1 June–31 July 2017 1 June–31 August 2017 Depth (m) N r2 Regression lines Average N r2 Regression lines Average (y-x) (y-x) 0.1 61 0.68 y=0.67x + 1.18 -0.08 92 0.60 y=1.20x - 1.24 -0.23 0.2 61 0.80 y=0.93x - 0.09 -0.28 92 0.79 y=0.95x - 0.35 -0.50 0.4 61 0.79 y=1.26x - 0.78 -0.25 92 0.82 y=0.99x - 0.05 0.03

Test 3 (Iffiartafik) Test 4 (Sandnes) 1 June–31 July 2017 1 June–31 August 2017 Depth (m) N r2 Regression lines Average N r2 Regression lines Average (y-x) (y-x) 0.1 61 0.85 y=1.08x-0.41 0.07 92 0.39 y=0.73x+2.2 0.27 0.2 No data No data No data No data 92 0.88 y=0.98x-0.03 -0.12 0.4 61 0.97 y=1.36x - 0.56 0.02 92 0.92 y=1.14x - 0.04 -0.13 Supplementary Table S4: Overview of the environmental parameters monitored at the five study sites and the equipment used.

Data type Kangeq Ersaa Qoornoq Iffiartarfik Sandnes

Air temperature CS215 Temperature *Data from an official CS215 Tinytag MP100A Temperature & RH probe meteorological station Temperature & RH (Gemini Data Loggers) & RH probe (Campbell (Campbell Scientific) located 5 km to the probe Scientific) South was used. (Campbell Scientific) Rain 52202 Tipping Bucket *Data from an official 52202 Tipping 52202 Tipping Bucket 52202 Tipping Bucket Raingauge meteorological station Bucket Raingauge Raingauge Raingauge (Campbell Scientific) located 5 km to the (Campbell (Campbell Scientific) (Campbell Scientific) South was used. Scientific) Snow cover Automatic camera Automatic camera Automatic camera

Soil temperature 107 temperature Tinytag 107 temperature Tinytag 107 temperature probes (Campbell (Gemini Data probes (Campbell (Gemini Data Loggers) probes (Campbell Scientific) Loggers) Scientific) Scientific)

Soil moisture Theta Probe SM300 probe Theta Probe SM300 probe SM300 probe (Delta-T Devices Ltd, (Delta-T Devices Ltd, (Delta-T Devices (Delta-T Devices Ltd, (Delta-T Devices Ltd, Cambridge, UK) Cambridge, UK) Ltd, Cambridge, Cambridge, UK) Cambridge, UK) UK)