High Affinity Methanotrophs Are an Important Overlooked Methane Sink - - PowerPoint PPT Presentation

High Affinity Methanotrophs Are an Important Overlooked Methane Sink in the Arctic and Global Methane Budgets

1 Youmi Oh, Qianlai Zhuang, Licheng Liu, Lisa R. Welp Maggie C.Y. Lau, Tulli C. Onstott, David Medvigy, Gustaf Hugelius, Ludovica D'imperio, Bo Elberling, Stefan Schwietzke, Xin Lan, Sourish Basu, Lori Bruhwiler, and Edward Dlugokencky

NOAA ESRL Global Monitoring Annual Conference 2019

Uncertainties in natural arctic methane budget

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Tarnocai et al. 2009; McGuire et al., 2012; Hinzman et al., 2013; Bruhwiler et al., 2014; Lau et al., 2015; Tan et al., 2015; Saunois et al. 2016

Introduction

gCH4m-2yr-1

• 2

Methane models Atmospheric Inversions

Tg/yr

10 20 30 40

Arctic Methane Budget (> 53°N)

Net Methane Emissions Simulated by CLM 4.5

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MG

HAM LAM High affinity methanotroph Low affinity methanotroph Methanogen

• a. Wetland

LAM SOC

CH4 CH4 [CH4]air CH4

Introduction

• b. Upland

[CH4]air

Le Mer and Roger, 2001; Christiansen et al., 2015

Biogeographic differences in methanotrophs

HAM MG

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ε: Growth efficiency mE: Maintenance energy

MG

HAM LAM High affinity methanotroph Low affinity methanotroph Methanogen

Permafrost ε mE mE

• a. Wetland

t=1,2,3… t=1,2,3…

LAM MG SOC

CH4 CH4 [CH4]air CH4

ε SOC

Method

ε

• b. Upland

mE

t=1,2,3…

[CH4]air

ε HAM Zhuang et al., 2004; Zhuang et al., 2006; Zhuang et al., 2013; Oh et al., 2016

I added microbial and permafrost dynamics into TEM

Three model setups for factorial analysis

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• Simulation was conducted at a spatial resolution of 0.5°×0.5° from north of

50°N for contemporary period (2000-2016) and future projection (2016-2100) Model Setup XPTEM-XHAM PTEM-HAM TEM Permafrost Dynamics ON ON OFF High Affinity Methanotrophs ON ON OFF Microbial Dynamics ON OFF OFF

Zhuang et al., 2004; Zhuang et al., 2006; Zhuang et al., 2013; Oh et al., 2016

Method

Annual Pan-Arctic Net Methane Emission Year

2000 2002 2004 2006 2008 2010 2012 2014 2016 Tg

C H 4 /yr

20 25 30 35 40 45 50 55 60 65

New models show lower CH4 emissions in 2000-2016

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Results

XPTEM-XHAM

Atmospheric Inversion

Bruhwiler et al., 2014;Lau et al., 2015; Tan et al., 2015; Saunois et al. 2016

Year

2020 2030 2040 2050 2060 2070 2080 2090 2100 Tg

C H 4 /yr

20 30 40 50 60 70 80 90

Annual Pan-Arctic Net Methane Emission for RCP 8.5

XPTEM-XHAM PTEM-HAM TEM

New models project smaller future CH4 emissions

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Schaefer et al., 2011; Koven et al., 2011; Schuur et al., 2013; Lawrence et al., 2015

Previous Models

Results

HAM shows a better adaption strategy in the future

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Von Stockar and Liu, 1999; Wieder et al., 2013; Trimmer et al., 2015

Results

Year

2020 2030 2040 2050 2060 2070 2080 2090 2100

Tg

C H 4 /yr

10 15 20 25 30 35 40

Temperature-sensitive Pan-Arctic Net Methane Emission for RCP 8.5

XPTEM-XHAM XPTEM-XHAM with Microbial Adaptation

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Temperature Increase Permafrost Thaw Methane Emission Methanogen Activity Soil Water Increase

+ + + + + +/-

Well Constrained Poorly Constrained Microbial Dynamics and Composition High Affinity Methanotroph Activity

+

• Implication on arctic methane feedbacks

Implication

Oh et al., 2016

Models overestimated global natural methane emissions

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Smith et al., 2000; Curry et al., 2007; Dutaur and Verchot, 2007; Saunois et al. 2016

Introduction

Natural - BU Natural - TD Ag/Waste - BU Ag/Waste - TD Fossil Fuel - BU Fossil Fuel - TD

• Bio. Burning - BU
• Bio. Burning - TD

Tg

C H 4 yr

• 1

500 1000

Mean Annual Methane Emissions from 2003 - 2012

BU: Bottom-Up Methane Models TD: Top-Down Atmospheric Inversions

• The current estimation of global methane soil sink is 30 TgCH4yr-1, but

with a huge uncertainty (7 to >100 TgCH4yr-1)

The Global methane soil sink can be up to 3 times larger

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Zhuang et al., 2004; Zhuang et al., 2006; Nachtergaele, Freddy, et al. 2010

Results

Criteria 1 (TgCH4 yr-1) – max. SOC threshold HAM only SOC 5% SOC 1% SOC 0.5% LAM only 90 90 73 60 33 Criteria 2 (TgCH4 yr-1) – max. pH threshold HAM only pH 6 pH 7 pH 8 LAM only 90 76 64 46 33

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Inversion simulation using CarbonTracker-CH4

CarbonTracker- CH4 XPTEM-XHAM In-situ and Satellite data Airborne measurement

Observational Constraints Current Simulation GOSAT NOAA Aircraft HIPPO BARCA CARIBIC ARCTAS CARVE AIRS TM5

Peters et al., 2005; Bruhwiler et al., 2011; Bruhwiler et al., 2014

Atmospheric Inversion

NOAA in-situ data

Take Home Message

• We simulated less current and future net methane emissions in the

Arctic by considering microbial dynamics of HAM and MG and permafrost dynamics

• The preliminary results show that the global methane soil sink can

be up to 3 times larger than the current estimation

• Limitation and future research
• Validation of the model and hypothesis using atmospheric inversions
• Validation of the model for sites with a broader range of pH, SOC, and

vegetation types using both high and low affinity methanotrophs using meta-data 13

Summary

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Acknowledgement

NASA Earth and Space Science Fellowship