In a warming climate, why do we see

decreasing heat flux in the Arctic Ocean

Under the guidance of

Prof. Yanping Li and Dr. Daqing Yang

By

Harsh Beria

-Mitacs Intern

IIT Kharagpur

Study area

Figure 1. Pan-Arctic view

(Source: http://picshype.com/arctic-ocean-on-map/figure-1/32917)

Background

● 70% flow into the Arctic from Siberian rivers, the rest 30% comes

from North American rivers (Yukon and Mackenzie).

● 7% increase in fresh water flow into the Arctic Ocean from the six

Siberian rivers.

● Increased water temperature due to warmer climate.

●

● Expected increase in heat flux, but trend analysis shows decreasing

trends in heat flux.

86, 400 p Q TH C N

Data

● Streamflow, water temperature (10 days resolution, called decadal)

obtained from Russian archival sources (Lammers et al., 2007)

● Time period: 1929 – 2003 (most data lies between mid 1930s to

early 1990s).

● Limitation: North American datasets only date back to 1970s.

Methodology

● Non-parametric change point estimator (Pettitt, 1979).

● Single most significant change point calculated, to characterize the

impact of multiple dams, instead of conventional pre vs post dam

approach.

● Non-parametric Mann-Kendall test used for long term trend

detection, using pre-whitening procedure (accounting for AR(1)

processes)

Reservoir regulation

0

500

1000

1500

2000

1930 1940 1950 1960 1970 1980 1990 2000

Mea

n a

nnual

flu

x (

PJ/

dec

ade)

Mean annual flux from major 6 Eurasian rivers

0

500

1000

1500

2000

1930 1940 1950 1960 1970 1980 1990 2000

Mea

n a

nnual

flu

x (

PJ/

dec

ade)

Year

Mean annual flux from 4 major regulated rivers

0

50

100

150

200

250

1930 1940 1950 1960 1970 1980 1990 2000

Mea

n a

nnual

flu

x (

PJ/

dec

ade)

Year

Mean annual flux from 2 major unregulated rivers

Effect of reservoir regulation

Peak flow: 5th June

Peak flux: 25th June

Peak water temp: 25th July

Effect of reservoir regulation

● Increase in winter low flows (40% - 90% at p = 0.01) – No impact

on heat flux

● Peak flow - Decrease in flow (-5%), increase in water temperature

(0.21 °C), increase in flux (11%)

● Peak flux – Decrease in flow (-1.1%), decrease in water temperature

(-0.1 °C), decrease in flux (-3.9%)

● Peak temperature – Decrease in flow (-17% at p = 0.01), decrease in

water temperature (-0.3 °C), decrease in flux (-18% at p = 0.01)

● Decrease in annual flux from 426 PJ/decade to 381 PJ/decade

(-10.7%) [p = 0.06]

Impact of climate change

Peak flow: 5th June

Peak flux: 25th June

Peak water temp: 25th July

Impact of climate change

● Increase in winter precipitation (up to 40 mm), leading to

increase in streamflow when the snow pack melts.

● Increase in winter air temperature, leading to warmer water

(up to 3.8 °C increase in peak temperature).

● Increased precipitation and warmer climate leads to

increased heat flux discharge in a natural climate setting

(without any major dams).

Conclusions

●Dams change the flow regime, leading to an

earlier peak flow when temperatures are low.

●Due to lower temperatures at the time of peak

floods, less heat flux flows into the Arctic

ocean.

How is the Arctic changing?

● Flow regimes are changing immensely, with the peak flows

occurring 3-5 days before normal.

● Flow of heat flux has decreased substantially into the Arctic Ocean.

● Increased freshwater inflow into the Arctic Ocean may stop the

thermohaline circulation, causing rapid cooling in Europe.

● Recent study by Fossheim et al. 2015, shows a drastic change in

spatial distribution of fish communities, with Arctic shelf fish

retracting northwards.

Future Scope

● Incorporate North American rivers (Yukon and

Mackenzie) into the heat flux calculations, and assess the

impact of reservoirs.

● Use climate reconstruction to naturalize flows for North

American rivers, for long term climate assessment.

● Estimation of water balance components and permafrost

degradation.

Thank You