# Presentation: 905482

**Historical and Future Changes in Dissolved Oxygen in the Bern 2D Climate Model**

- North Pacific Carbon Cycle Workshop, Seattle, June 2004

- Gian-Kasper Plattner
-        IGPP, UCLA

## Bern Climate Model of Reduced Complexity

**GEOMETRY**

**COMPONENTS**

- - 29 vertical layers

-  Anthropogenic and Natural Radiative Forcings:
- --> reconstructed until 2000, SRES scenarios until 2100
-  Climate Sensitivity: 3.7 oC

## Modeled Oxygen and Heat Fluxes

- (Plattner et al., GBC 2002)

## Modeled Oxygen Changes1990s – 1970s

- (Plattner et al., GBC 2002)

**Mechanisms:**
**- Circulation and convection**
- - Solubility
- - Biology

## North Pacific Changes: Model vs. Data

** ****1990s – 1970s**

- (Plattner et al., GBC 2002)

## Modeled Historical Oxygen Changes

- (a) O2 (mmol m-3) 1990s – 1950s

- (b) O2 (mmol m-3) 1990s – 1970s

-           ATLANTIC                         INDIAN                      PACIFIC

-           ATLANTIC                         INDIAN                      PACIFIC

- 10

- -10

- 10

- -10

- -23

- -23

## Modeled Future Oxygen Changes

- (a) O2 (mmol m-3) 2020s – 1990s, SRES B1

- (b) O2 (mmol m-3) 2090s – 1990s, SRES B1

-           ATLANTIC                         INDIAN                      PACIFIC

-           ATLANTIC                         INDIAN                      PACIFIC

- 60

- -60

- 30

- -30

- -80

- -200

## Modeled Future Oxygen Changes

**Modeled Future Oxygen Changes**

- (a) O2 (mmol m-3) PACIFIC 2020s – 1990s

- (b) O2 (mmol m-3) PACIFIC 2090s – 1990s

-     SRES B1 anth               SRES A1B anth                 SRES A1FI anth

- 10

- -10

- -60

- 60

- -90

- -120

## Modeled Future Oxygen Changes

- (a) O2 (mmol m-3) year 2500 – 2000, WRE550 anth

- (b) O2 (mmol m-3) year 2500 – 2000, WRE1000 anth

-           ATLANTIC                         INDIAN                      PACIFIC

-           ATLANTIC                         INDIAN                      PACIFIC

- 150

- -150

- 70

- -70

- -250

- -110

## Summary

-   Global mean dissolved oxygen is reduced by 0.45 mmol m-3 between the 1970s and the 1990s. Reductions until 2100 are around 8 mmol m-3 on average (different SRES scenarios give a range of 7 to 10 mmol m-3).
-   North Pacific reductions are 0.29 mmol m-3 from the 1970s to the 1990s, and 11 mmol m-3 until 2100.
-   Largest changes occur in the North Atlantic (to a depth of about 3000 m), the top 1000 m of the North Pacific and the Southern Ocean.
-   Changes in circulation and convection are dominant. Solubility changes contribute about 20%. Changes in organic matter cycling (reduced new production) are modestly counteracting the oceanic oxygen loss. The solubility contribution increases to over 30% in simulations of future changes up to year 2100.
-   The large scale oxygen outgassing impacts global carbon budget estimates based on atmospheric oxygen measurements.

## The end

## Summary

-   Significant oxygen changes are modeled** **in all basins due to variations in radiative forcing (natural and anthropogenic).
-   Global mean dissolved oxygen is reduced by 0.45 mmol m-3 between the 1970s and the 1990s. Reductions until 2100 are around 8 mmol m-3 on average (different SRES scenarios give a range of 7 to 10 mmol m-3).
-   North Pacific reductions are 0.29 mmol m-3 from the 1970s to the 1990s, and 11 mmol m-3 until 2100.
-   Modeled changes (zonally averaged) are much smaller than observed changes reported in the literature.
-   Largest changes occur in the North Atlantic (to a depth of about 3000 m), the top 1000 m of the North Pacific and the Southern Ocean.
-   The changes are predominantly driven by changes in circulation and convection and to lesser extent by changes in solubility (20%). Changes in organic matter cycling (reduced new production) are modestly counteracting the oceanic oxygen loss. The solubility contribution increases to over 30% in simulations of future changes up to year 2100.
-   The large scale oxygen outgassing impacts global carbon budget estimates based on atmospheric oxygen measurements.

## Modeled Historical Oxygen Changes

**Modeled Historical Oxygen Changes**

- O2 (mmol m-3)
-                1990s – 1950s, anth

- 1990s – 1970s, anth

- NORTH PACIFIC

## Modeled Future Oxygen Changes

- O2 (mmol m-3)
-   2020s – 1990s, SRES B1 anth

- 2090s – 1990s, SRES B1, anth

- NORTH PACIFIC

## Changes in NADW FormationIPCC TAR Models vs. Bern Model (red)

## Global Mean Surface Air Temperature Rise Model vs Obs. 1850 – 2000

## Ocean Heat Content AnomalyModel vs Obs. 1850 – 2000

- (Plattner et al., GBC 2002)

## Modeled Historical Oxygen Changes

**Modeled Historical Oxygen Changes**

-  O2 (mmol m-3) 1990s – preindustrial

-           ATLANTIC                         INDIAN                      PACIFIC

- 25

- -25

- -50

- -50

## Global Mean Surface Air Temperature RiseSRES B1, different forcings incl.

## Modeled Historical Oxygen Changes

- (a) O2 (mmol m-3) 1990s – 1950s, anth

- (b) O2 (mmol m-3) 1990s – 1970s, anth

-           ATLANTIC                         INDIAN                      PACIFIC

-           ATLANTIC                         INDIAN                      PACIFIC

- 15

- -15

- 15

- -15

- -65

- -25

- -20

- -55

## Modeled Circulation Changes

- Streamfunction (Sv), Year 2100 – preindustrial

## Modeled Temperature Changes

**Modeled Temperature Changes**

- (a) Temp (oC) 1990s – 1970s

- (b) Temp (oC) 2090s – 1990s, SRES B1

-           ATLANTIC                         INDIAN                      PACIFIC

-           ATLANTIC                         INDIAN                      PACIFIC

- 6

- -6

- 0.5

- -0.5

## Modeled Salinity Changes

- (a) Salt (psu) 1990s – 1970s

- (b) Salt (psu) 2090s – 1990s, SRES B1

-           ATLANTIC                         INDIAN                      PACIFIC

-           ATLANTIC                         INDIAN                      PACIFIC

- 1

- -1

- 0.03

- -0.03

## Modeled Phosphate Changes

- (a) PO4 (mmol m-3) 1990s – 1970s

- (b) PO4 (mmol m-3) 2090s – 1990s, SRES B1

-           ATLANTIC                         INDIAN                      PACIFIC

-           ATLANTIC                         INDIAN                      PACIFIC

- 0.7

- -0.7

- 0.1

- -0.1