1. Radiation Budget in the Shelf Areas of the Laptev Sea
Sebastian Hellmann
Jens Hölemann, Tilman Dinter, Birgit Heim, Astrid Bracher
LenaDNM Workshop, Bremerhaven
07 December 2016

2. Motivation&Objectives Current results Ideas and Outlook Summary
Outline:
Motivation, investigation area and Objectives
First results
Modelling of radiation budgets in Laptev Sea
Ideas and Outlook
Remote sensing data for multi-annual time series
Summary
Sebastian Hellmann: Radiation Budget in the Shelf Areas of the Laptev Sea
2/14

3. Motivation&Objectives Current results Ideas and Outlook Summary
Sebastian Hellmann: Radiation Budget in the Shelf Areas of the Laptev Sea
3/14

4. Motivation&Objectives Current results Ideas and Outlook Summary
Siberian Laptev Sea:
S02, S06, S22: no riverine influence
S16, S19: influenced by river plume
Sebastian Hellmann: Radiation Budget in the Shelf Areas of the Laptev Sea
4/14

5. Motivation&Objectives Current results Ideas and Outlook Summary
Motivation to analyse CDOM:
Light = limiting factor for biological activities
CDOM limits solar radiation into water
Radiation  ice cover + development  high CDOM absorption changes radiation budget
Why do we use remote sensing data:
Remote area, very limited access
Remote sensing  broad seasonal measurements
Inter- and intra-annual changes
Sebastian Hellmann: Radiation Budget in the Shelf Areas of the Laptev Sea
5/14

6. Motivation&Objectives Current results Ideas and Outlook Summary
Difficulties for remote sensing investigations:
ice cover
river plume
Sebastian Hellmann: Radiation Budget in the Shelf Areas of the Laptev Sea
6/14

7. Motivation&Objectives Current results Ideas and Outlook Summary
Two main objectives:
Question I: absorption in which part of the water column?  influences on radiation budget
Question II: are there changes in CDOM- absorption over the last decades  climate effects
Sebastian Hellmann: Radiation Budget in the Shelf Areas of the Laptev Sea
7/14

8. Motivation&Objectives Current results Ideas and Outlook Summary
Solar irradiance (up+downwelling) into water
Radiative Transfer Model SCIATRAN:
developed at Uni Bremen, free to use, but registration required
highly resolved solar spectrum (3nm convolved, nm)
consider Chl, CDOM, SPM in water
Consider aerosols and gaseous absorption in atmosphere
SZA between 54° and 80°
hourly values for a clear and cloud covered summer day
stations in river plume
stations on shelf outside river plume
--- cloudcovered sky clear sky
Sebastian Hellmann: Radiation Budget in the Shelf Areas of the Laptev Sea
8/14

9. Motivation&Objectives Current results Ideas and Outlook Summary
Solar irradiance (up+downwelling) into water
Solar irradiance (up+downwelling) into water
stations in river plume
stations on shelf outside river plume
--- cloudcovered sky clear sky
Sebastian Hellmann: Radiation Budget in the Shelf Areas of the Laptev Sea
8/14

10. Motivation&Objectives Current results Ideas and Outlook Summary
True colour satellite image
ESA-MERIS (L1b), 20 Sept 2010
Sebastian Hellmann: Radiation Budget in the Shelf Areas of the Laptev Sea
9/14

11. Motivation&Objectives Current results Ideas and Outlook Summary
Image of CDOM-absorption (L2)
POLYMER-Algorithm, 20 Sept 2010
CDOM-Abs. aCDOM (443nm) [m-1]
Sebastian Hellmann: Radiation Budget in the Shelf Areas of the Laptev Sea
10/14

12. Motivation&Objectives Current results Ideas and Outlook Summary
Image of CDOM-absorption (L2)
POLYMER-Algorithm, 20 Sept 2010
aRS [m-1]
ain-situ [m-1]
CDOM-Abs. aCDOM (443nm) [m-1]
Sebastian Hellmann: Radiation Budget in the Shelf Areas of the Laptev Sea
10/14

13. Motivation&Objectives Current results Ideas and Outlook Summary
Image of CDOM-absorption (L2)
C2X-Algorithm, 20 Sept 2010
CDOM-Abs. aCDOM (443nm) [m-1]
Sebastian Hellmann: Radiation Budget in the Shelf Areas of the Laptev Sea
11/14

14. Motivation&Objectives Current results Ideas and Outlook Summary
Image of CDOM-absorption (L2)
POLYMER-Algorithm, 20 Sept 2010
aRS [m-1]
ain-situ [m-1]
CDOM-Abs. aCDOM (443nm) [m-1]
Sebastian Hellmann: Radiation Budget in the Shelf Areas of the Laptev Sea
11/14

15. Challenges to obtain high quality CDOM distribution:
Investigation Area Motivation Current results Ideas and Outlook Summary
Challenges to obtain high quality CDOM distribution:
relationship between CDOM and Chlorophyll
Laptev Sea riverine influenced case-2 water
global relationships not valid in this shelf sea
frequent cloud cover inhibits continuous time series and
Comparison with sparse in-situ measurements
Sebastian Hellmann: Radiation Budget in the Shelf Areas of the Laptev Sea
12/14

16. Challenges to obtain high quality CDOM distribution:
Investigation Area Motivation Current results Ideas and Outlook Summary
Challenges to obtain high quality CDOM distribution:
relationship between CDOM and Chlorophyll
Laptev Sea riverine influenced case-2 water
global relationships not valid in this shelf sea
frequent cloud cover inhibits continuous time series and
Comparison with sparse in-situ measurements
resuspension occurs often
in shallow parts of the sea
penetration depth very low
However: Remote sensing data
are the only continuous data
Sebastian Hellmann: Radiation Budget in the Shelf Areas of the Laptev Sea
12/14

17. Investigation Area Motivation Current results Ideas and Outlook Summary
Summary and Outlook:
Question I: Energy transfer is limited by CDOM but also by solar elevation
Question II: Developing an adapted retrieval algorithm to avoid underestimation of CDOM
Question II: Using this algorithms to generate a time series and analyse potential feedback to climate changes
Sebastian Hellmann: Radiation Budget in the Shelf Areas of the Laptev Sea
13/14

18. Investigation Area Motivation Current results Ideas and Outlook Summary
Sebastian Hellmann: Radiation Budget in the Shelf Areas of the Laptev Sea
14/14

19. Motivation&Objectives Current results Ideas and Outlook Summary
True colour satellite image
ESA-MERIS (L1b), 01 Sept 2011
Sebastian Hellmann: Radiation Budget in the Shelf Areas of the Laptev Sea
10/14

20. Motivation&Objectives Current results Ideas and Outlook Summary
What is “CDOM”?
Chromophoric or coloured dissolved organic matter
Compounds of organic carbon, smaller than 0.2 µm
Absorbs light predominantly in UV-blue range  colour of water changes to yellow  gelbstoff
Laptev Sea: CDOM mainly transported by Lena river from Mid-Siberian mountain region
Distinction between marine and terrestrial origin possible (slope ratio, FDOM analysis)
Sebastian Hellmann: Radiation Budget in the Shelf Areas of the Laptev Sea
3/14

21. Motivation&Objectives Current results Ideas and Outlook Summary
Image of CDOM-absorption (L2b)
ESA-MERIS-C2R, 01 Sept 2011
CDOM-Absorption aCDOM (=443 nm) [m-1]
Sebastian Hellmann: Radiation Budget in the Shelf Areas of the Laptev Sea
11/14