180°

165°W

HiiumaaSaaremaa

HelsinkiHyyti ä l ä

Kaarina

NurmesVario

SodankylaKevo

Ny-ÅlesundQaanaaq

TuraTiksi Chokurdakh

Mirny

Yakutsk Oymyakon

Glaciers in Suntar-Khayata region

S.W.L

105°E 120°E 135°E 150°E 165°E

90°W75°W60°W45°W30°W15°W0°

15°E

30°E

45°E

60°E

75°E

90°E

150°W

135°W

120°W

105°W

Terrestrial ecosystem

Atmosphere

Cryosphere

Greenhouse gas

Marine ecosystem

Sea Ice and ocean environment

Snow survey lines

Permafrost survey lines

Airliner

Solid-lines (yellow, orange, pink, blue): Ship

Icebreakers’observation area

Churchill

Fort Smith

Fort Providence

Norman Wells

InuvikPrudhoe Bay

Poker Flat

FairbanksBarrow Anchorage

LSSL

MIRAI MR14-05

MIRAI MR15-03

MIRAI MR13-06

HAKUHO MARU

OSHORO MARU

MIRAI MR12-E03

Warming ampli�cation in the Arctic

• Intensi�cation of atmospheric circulation

• Reduction of ocean circulation

• Change of snow area

• Sea level rise by glacier and ice-sheet melting

• Change of carbon cycle

• Change of CO2 sink

• Change of heat transport

Increase of extreme events

Heattransport

Cloud Blackcarbon

Snow Sea iceGlacier microorganisms

Surface albedo

2 Arctic system for global climate and future change

4 Projection of sea ice distribution and Arctic sea routes

• Change of sea ice distribution and rafting e�ect

• Change of thermohaline circulation and heat budget

• Projection of sea ice extent and Arctic sea routes

3 a Impacts on weather in Japan

3 b Impacts on marine ecosystem and �sheries

• Cold wave and heavy snow in Japan

• Change of primary species of �sh

• In�uence on mid-latitude • Ocean acidi�cation• Change of primary production

• Stratosphere-troposphere interaction• Change of atmos. circulation

1 Mechanism of warming ampli�cation in the Arctic

StratosphereTroposphere interaction

Atmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heatingAtmospheric heating

Ice-albedo feedback

Cloud-sea ice interaction

Ocean-sea ice interaction

Impact on marine ecosystem

Stratospheric circulation

Tropospheric circulation

Stratosphere–Troposphere interaction

Atmospheric heating

Cloud-sea ice interaction

Black carbon

Ice-sheet

Cloud

Snow

Sea ice

Ship

Ocean-sea ice interaction

Marine ecosystem

Ocean circulation

Impact on marine ecosystem

Warming ampli�cationin the Arctic

Ice-albedo feedback

Ice-albedo feedback

SnowGlacier

(Permafrost)Boreal forest

Impact of the Arctic warming on the mid latitude

Japan

CO2 CH4

Tundra

Degrading underground ice (yedoma) in the per-mafrost zone of the North Slope, Alaska(Courtesy of Masao Uchida, National Institute for Environmental Studies; Go Iwahana, International Arctic Research Center)

Ice-albedo feedback

Impact of the Arctic warming on the mid latitude

Stratospheric circulation

Tropospheric circulation

Stratosphere–Troposphere interaction

Atmospheric heating

Cloud-sea ice interaction

Black carbon

Ice-sheet

Cloud

Snow

Sea ice

Ship

Ocean-sea ice interaction

Marine ecosystem

Ocean circulation

Impact on marine ecosystem

Warming ampli�cationin the Arctic

Ice-albedo feedback

Ice-albedo feedback

SnowGlacier

(Permafrost)Boreal forest

Impact of the Arctic warming on the mid latitude

Japan

CO2 CH4

Tundra

Simulation (AR5, RCP4.5)

Simulation (AR4, SRES A1B)

Observation

2.0

1.5

1.0

0.5

0.0

-0.5

19001850 1950 2000 2050 2100

0

2

4

6

8

10

Average in the Arctic (north of 60°N)

(from the data of UK Met. O�ce)

(from the IPCC reports)

Surface air temperature change

Change of sea ice area in September

Surf

ace

air t

empe

ratu

re c

hang

esi

nce

the

begi

nnin

g of

the

20th

cen

tury

(°C)

Sea

ice

area

(106 k

m2 )

Global average

0.9°C 2.0°C

(Upper) The mean surface air temperature in the Arctic has clearly increased twice as rapidly as that of the global mean, both in the last 100 years and in the last 40 years.(Lower) The Arctic sea ice extent in September has decreased faster than what has been simulated by cli-mate models. Moreover, the decrease is projected to continue through the 21st century.

Map of GRENE-Arctic observation activities

About the projectArctic Climate Change Research Project: Rapid Change of the Arctic Climate System and its Global In� uences

“Green Network of Excellence” (GRENE) Program by Ministry of Education, Culture, Sports, Science & Technology, Japan (MEXT)

Core Institute: National Institute of Polar Research

Associated Institute: Japan Agency for Marine-Earth Science and Technology

Period: July 2011—March 2016

http://www.nipr.ac.jp/grene/

For further details: Final Report of GRENE Arctic Climate Change Research Project (Japanese edition only)

Editing/PublicationInter-university Research Institute CorporationResearch Organization of Information and SystemsNational Institute of Polar Research10-3 Midori-cho, Tachikawa-shi, Tokyo 190-8518, JapanTelephone: +81-42-512-0922http://www.nipr.ac.jp

IssuedAugust 31, 2016Front cover: Meltwater stream over a glacier surface darkened by glacier microorganisms in Greenland(Photo by Shin Sugiyama, Hokkaido Univ.)

Arctic Climate ChangeResearch ProjectRapid Change of the Arctic ClimateSystem and its Global In� uencesGRENE Arctic Climate Change Research ProjectSummary of outcomes, 2011–2016

Warming ampli� cation in the Arctic and its global impact The key to Arctic climate change is Arctic warming ampli� cation (AA). AA leads to the change in sea ice extent and then to the realization of the Arctic sea routes. It also a� ects the global climate, such as atmospheric circulation, cryosphere, and the carbon cycle. Moreover, AA will alter marine chemical components and the living environment for plankton, and hence have impacts on the major � sh species and � sheries. AA will also in� uence the mid-latitude weather and climate, and bring cold and heavy snow to Japan in winter. The Arctic, the fastest-warming place on

What is happening now in the Arctic, under global warming?In warming due to anthropogenic increases in carbon dioxide

concentration, the surface temperature in the Arctic is increasing with a speed that is more than double the global average. We call this “Arctic warming ampli� cation,” and an understanding of its mechanism is urgently needed.

Reduction of sea ice extent in the Arctic Ocean is continuing, and an abrupt decrease since the 2000s is especially noticeable. Owing to this change, potential for regular ship navigation through the Arctic Ocean have increased, and they have become broadly known as “Arctic sea routes.” � e reduction of the sea ice extent

and the warming of the ocean are expected to lead to changes not only in the physical and chemical ocean environment, but also to changes of marine ecosystems.

Looking at the land area, many glaciers distributed around the Arctic are retreating. � e Greenland ice sheet, the largest ice mass in the northern hemisphere, is also melting markedly, and the � ow-out or collapse from its terminal glacier is serious. � is will be a concern in terms of the world sea level rise. Moreover, the duration of the snow season is decreasing. In such ways, snow and ice have been showing great changes, and thus great impacts on atmospheric circulation and terrestrial biology are foreseen. Changes in terres-

trial biological activity will alter the amount of atmospheric carbon dioxide absorption by vegetation, and will a� ect global warming as feedback. Although it is far away from Japan, we cannot turn a blind eye to Arctic climate change, since we are a� ected by it, too.

In order to grasp these abrupt changes in the Arctic, to under-stand the mechanism, and to contribute to future climate change projection, we conducted the Green Network of Excellence Program (GRENE) Arctic Climate Change Research Project “Rapid Change of the Arctic Climate System and its Global In� uences” for � ve years between 2011 and 2016. 39 institutes all over Japan have par-ticipated in the project, and more than 360 Japanese scientists tack-

led all aspects of the Arctic climate system. Comprehensive Arctic research incorporating multidisciplinary work and collaborations between observation and modeling have been realized.

Here we will report the scienti� c results achieved. In the proj-ect, four strategic research targets were presented and the outcomes for each target are described on the following pages. Finally, the mutual relationships between each target and a synthesis of “Rapid Change of the Arctic Climate System and its Global In� uences” are shown in the � ow diagram on the back page.

Earth!

Retreating Suntar-Khayata Mountain Glacier in Siberia region(Photo by Hiroyuki Enomoto, National Institute of Polar Research)

Warming at surface

Pre-warming On-warming

Seasonal cycle of surface warming

Sea ice and snow

Sea ice and snow

Cloud

Increase in absorbed sunlight due to retreat of sea ice and exposure of sea surface

JUN-JUL Increase in ocean heat storageAUG-SEP

WarmingSea ice melt and temperature rise Relaxation of warming

Heat release from the ocean to the atmosphere.Trapping of heat near the surface, increase in cloud, etc.

NOV-JANSummer

Sunlight

Ocean

JAN

15

10

5

0

-5

Tem

pera

ture

cha

nge

from

the

end

of 2

0th

cent

ury

to th

e en

d of

21s

t cen

tury

(°C)

FEB MAR APR May JUN JUL AUG SEP OCT NOV DEC

Others(trapping of heat, increase in cloud, etc.)

Ocean heat uptake and release

Heating by ice-albedo feedback due to sea ice reduction

Warming at surfaceWarming at surface

Greenhousee�ect

Inhibition of convention

High sensitivityto the temperature

increase

Deceleratedpolar vortex

Polar vortex

Stronger Siberian High Negative AO

Cold in Euro-Atlantic region

Jet stream

Cold in Siberia and Far East

Meandering jet stream

Stra

tosp

here

Trop

osph

ere

2015/09/11

Russia

Laptev Sea

East Siberian Sea

Alaska

Canada

Arctic change is advancing with potential global in� uence.

Quanti� cation of relative contribution to Arctic warming ampli� cation factors and their seasonality.

Climate change in the Arctic brings cold spells and snowstorms over Japan.

Changes and shi� s in the Arctic marine ecosystem have been evident.

� e Arctic sea routes: Feasible for sustainable use.

Mechanism of the impacts of Arctic change on weather and climate in Japan Fallen tree by a snowstorm (Photo by Shuhei Takahashi, Okhotsk Sea Ice Museum of Hokkaido)

Predicted (green line, forecasted at the end of May) and observed (white area) ice area on September 11, 2015

Icebreaker navigating the thin ice area(Photo by Kazutaka Tateyama, Kitami Institute of Technology)

Changes in snow cover duration during the past 30 years. The red area indicates shortening of the snow-covered period, while the blue area indicates lengthen-ing. There has been a signi� cant reduc-tion of snow cover duration in Europe.

The seasonal cycle of warming ampli� cation over the Arctic Ocean and its contributing factors. The black line shows the seasonal cycle of temperature increases from the end of the 20th century to the end of the 21st century averaged over the Arctic Ocean under the moderate warming scenario of RCP4.5. The contributions from the major factors contributing to the Arctic ampli� cation are shown by the colored lines (red, blue and green).

Ice-albedo feedback:As the temperature rises over the Arctic, snow and ice with high re� ectance re-treat, and the land and the ocean surfaces with low re� ectance are exposed. The absorption of sunlight then increases, leading to a further increase in tempera-ture and hence to a further increase in snow and ice retreat.

Snow sampling site near Denali National Park, Alaska(Photo by Yoshimi Tsukagawa, National Institute of Polar Research)

Trends of tree production in the second half of the 20th century inferred from tree ring analyses

Production increasedDecreased

Shortening

Trend of Snow Cover Duration [Day/30 years]

(Period: 1982-2013, excl. 1994, 1995)

-58.4 -38.9 -19.5 0.0 19.5 38.9 58.4 77.9 97.3

Lengthening

Sea Ice Thickness [m]

0 0.25

-180°

0°

150°

-30°

120°

-60°

90°

-150°

30°

-120

°

60°

-90°

0.5 0.75 1

An example of optimal routing based on the predicted sea ice thick-ness on 24 October, 2011 with the prediction system for Arctic sea routes

Phytoplankton

Benthos Benthos Feeders

Plankton & Fish Eaters

Zooplankton

Pelagic-Benthic scheme Pelagic-Pelagic scheme

Strategic Research Targets

Strategic Research Targets Strategic Research Targets

Strategic Research Targets Strategic Research TargetsUnderstanding the mechanism of warming ampli� cation in the Arctic

Evaluation of the impacts of Arctic change on weather and climate in Japan Evaluation of the impacts of Arctic change on marine ecosystems and fisheries

Understanding the Arctic system for global climate and future change Projection of sea ice distribution and Arctic sea routes1

3 3a b

2 4

CO2 emissionfrom the soil

Atmospheric CO2

CO2

Land Ocean

CO2 uptakeby vegetation

End

of 2

1st c

entu

ry

Pres

ent

CO2

Image of CO2 exchange in the Arctic

� e land and ocean in the Arctic have an important role in the uptake of CO2 from the atmosphere, which has been demon-strated by observations of atmospheric CO2 concentration. An increase in terres-trial uptake for the most recent 10 years was also suggested by the observed data.

Net uptake (or release) of CO2 by the land is a balance between net primary production of vegetation and soil respira-tion. It had been generally believed that the productivity of vegetation in cold re-gions such as the Arctic and sub-Arctic increased with warming. However, tree ring analyses for circum-arctic forest eco-systems revealed that not all regions in the Arctic and sub-Arctic show increases in tree growth. Tree growth is decreasing in some regions such as eastern Siberia, the Alaska Interior, and Canada. Moreover, soil respiration is expected to increase with temperature, which has been shown

by ecosystem model simulations, which suggests that CO2 uptake by the Arctic may not continue in the future.

� e GRENE-Arctic project has also revealed that snow duration is getting shorter and that reduction of sea ice ex-

tent may lead to extreme events such as heavy snowfall in mid-latitude regions due to changes in the atmospheric circu-lation pattern. � ese may also a� ect the Arctic and sub-Arctic ecosystems, result-ing in changes in the CO2 budget.

By analyzing future climate change projection datasets simu-lated by a number of climate models from the Coupled Model Intercomparison Project Phase 5 (CMIP5), we quantify the role of various factors contributing to the Arctic warming ampli� ca-tion and clarify their seasonality.

Increases in surface air temperature over the Arctic regions are smallest in summer but largest in winter. Over the Arctic Ocean in summer, ice-albedo feedback due to sea ice retreat has the largest tendency to warm the surface. However, the surface warming is smallest because of the large heat uptake by the open ocean. In autumn and winter, the heat stored in the Arctic Ocean in summer is released into the atmosphere. Moreover, there are a number of other factors that contribute to warming the surface: strong vertical stability in the atmosphere traps warming close to the surface; increased low-level clouds enhance the greenhouse e� ect by trapping more longwave radiation; surface warming sensitivity is larger in colder regions than in warmer regions due to the e� ect of the Stefan-Boltzmann law; and so on. As a conse-quence, the largest surface warming occurs in winter. Over the Arctic land, the ice-albedo feedback has a peak in the early sum-

mer. Its additional heat warms the land surface, though part of this enhances surface evaporation and reduces surface warming. In winter, on the other hand, the land has no heat storage to re-lease into the atmosphere. � erefore, the amplitude of seasonal variation for surface warming is smaller over the Arctic land than over the Arctic Ocean.

� is study clari� es the seasonality and the relative contribu-tions of various factors that were separately investigated, and also provides a comprehensive understanding of the mechanism of Arctic warming ampli� cation.

Arctic–mid-latitude climate linkage refers to possible impacts of Arctic climate change on mid-latitude climate and weather, which have recently been intensively studied. Severe weather in the northern mid-latitudes is o� en associated with meandering jet stream and the negative phase of the Arctic Oscillation (AO). Both observations and model simulations provide evidence that reductions in Arctic sea ice, or an increase in the Eurasian snow cover, tend to cause a negative AO phase, which is o� en preceded by weakening of the stratospheric polar vortex. � is evidence hints

at a stratospheric involvement in the Arctic–mid-latitude climate linkage. By arti� cially suppressing the stratospheric wave–mean � ow interactions in numerical experiments, tropospheric signals of the Arctic–mid-latitude climate linkage can be signi� cantly reduced, and thus we con� rm that the stratosphere plays a cru-cial role in the Arctic–mid-latitude linkage. � e results also im-ply that realistic representations of both Arctic surface boundary conditions and stratospheric processes are critical for improving predictions of weather and climate in the mid-latitudes.

� e Arctic Ocean has experienced signi� cant warming, freshen-ing, and ocean acidi� cation mainly caused by rapid reduction of sea ice. In the project Ecosystem Studies on the Arctic Ocean with Declining Sea Ice (ECOARCS), we investigated the impact of sea ice decreases on marine ecosystems. Our results show sev-eral forms of scienti� c evidence for changes in the marine eco-system: the dominance of larger phytoplankton due to faster sea ice retreat in spring in the shelf region of the Arctic Ocean and Bering Sea; and a northward shi� in the geographic distribution of the zooplankton community, benthos, � sh, and marine mam-mals. On the other hand, we found that the North Paci� c species of zooplankton transported into the Chukchi Sea (Arctic Ocean) is unlikely to establish stable Arctic populations in the near fu-ture due to large di� erences in geographic and life conditions.

Currently, a bloom of phytoplankton at the ice edge in spring to summer sinks down to the sea� oor and becomes food for the benthos (Pelagic-Benthic scheme, Figure below le� ). However, warming due to faster sea ice retreat may increase the population of zooplankton and � sh, which feed on phytoplankton at the ice edge (Pelagic-Pelagic scheme, Figure below right).

� e Arctic region will warm more rapidly than the global mean, and the resultant changes in Arctic environments could serve as an indication of global climate change, and should ring alarm bells not only for scientists, but also for the public. � at is why we need to continue to monitor Arctic environmental changes and responses of marine ecosystems to assess how they can or cannot adapt to these changes.

We have proposed empirical method to estimate timing of disappearance of sea ice, and proposed a simple model using just sea ice motion to evaluate volume transportation of upper ocean circulation, so called “Beaufort Gyre”, that delivers the heat into the central Arctic Ocean and af-fects fate of sea ice. Analyses using in-situ and satellite observation data have clari� ed that volume transportation of the oceanic Beaufort Gyre is determined by past sea ice motion from about four years previ-ously. We have also constructed methods to derive the timing of the disappearance of sea ice associated with ra� ing of sea

ice from satellite-derived high-accuracy sea ice motion data. We also conducted a study using a high-resolution numerical Arctic Ocean model to reveal the struc-ture of the heat transport system from the Atlantic to the Arctic, and the impact of meso-scale eddies on the advance/retreat of sea ice cover.

Another important theme of ours is seasonal-scale sea ice prediction, which is necessary for a decision of whether or not to take the Arctic route. We have improved the statistical method of the prediction using satellite remote-sensing data. In 2015, our prediction provided a

good forecast of the timing of summer ice retreat and the spatial pattern of the minimum ice cover. Our activity regard-ing the Arctic sea route included many other themes, such as the optimal routing of ships, engineering studies on ship/ice interaction, ship icing, economic evalua-tions, and a proposal of scenarios for the use of Arctic sea routes. With these mul-tidisciplinary e� orts, studies for realizing the sustainable use of Arctic sea routes have advanced greatly during the GRENE Arctic Research Project.