In a warming climate, why do we see decreasing heat flux in the Arctic Ocean?
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Transcript of In a warming climate, why do we see decreasing heat flux in the Arctic Ocean?
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
● 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
● 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.