# Presentation: 294015

## Ocean Currents, Sea Level, and Climate Change

***Dr. Lee-Lueng Fu***
***Project Scientist:  TOPEX/POSEIDON, Jason, OSTM***
***NASA/***
***Jet Propulsion Laboratory***
***California Institute of Technology***
***April 20, 2006***

## Planet Earth is the ocean planet... 

***“******How inappropriate to call this planet Earth, when clearly it is Ocean.” ***
***– ******Arthur C. Clarke ******–***

***Planet Earth is the ocean planet... ***

## The ocean affects climate through its huge capacity of water and heat:

**Has 97% of all Earth’s water,**
**The upper 3 m of the ocean has the same amount of heat as the entire atmosphere,**
**Absorbed 84% of the heat from global warming.**

## The Ocean’s Role in Climate:

- The oceans are the dominant reservoir for heat (and freshwater) in the climate system

- From Levitus et al., *GRL*, 2005

**Incoming heat**

**Outgoing heat**

**Net heat input causing global warming**

***Sun***

***Top of atmosphere***

## Challenger Expedition (1872~1875)

- H.M.S. Challenger sampled the ocean across the globe heralding the beginning of oceanography as a science discipline.

- Route of Challenger

## The harsh and vast ocean environment makes ocean observations from ships very scarce.

**The harsh and vast ocean environment makes ocean observations from ships very scarce.**

**January 2000**

## TOPEX/Poseidon ground track coverage every 10 days

**TOPEX/Poseidon ground track coverage every 10 days**

## Ocean currents transport heat and regulate climate change.  They can be measured from space via ocean surface topography. 

**geoid**

**sea surface**

**Ocean surface topography**

**H**

**L**

**Ocean currents move around the highs and lows of ocean surface topography.**

## L

**L**

**H**

**L**

**L**

## Slide 10

## 200 m

**200 m**

## 100 fold improvement in 25 years

**100 fold improvement in 25 years**

## Measurement Performance

**Measurement Performance**

**R. Cheney/NOAA**

## Ocean Surface Topography 

**Ocean Surface Topography **
**(TOPEX/Poseidon Sea Level – GRACE Geoid)**

**D. Chambers /UT Austin**

**3.4 m**

## Oceanic Conveyor Belt of Heat

**Oceanic Conveyor Belt of Heat**

**W.Broecker (Columbia U.); http://www.anl.gov/Media_Center/Frontiers/2003/**

**Overturning circulation**

## The overturning circulation of the North Atlantic (JPL ECCO Analysis)

**The *****overturning circulation***** of the North Atlantic (JPL ECCO Analysis)**

**Latitude**

**Northward Heat Flux (in 10****15**** watts) at 45o N**

**Year**

**Depth (m)**

**Cabanes, Fu, Lee/JPL**

**10****15**** watts (PW) > 300 times of the US energy consumption rate**

**Decrease by 0.07 PW**

## Monitoring El Niño

**Either direction (from****the warmer to the ****cooler medium).**

**Either direction (with some chemicals****being transferred predominantly in****one direction of the other).**

**Normal equatorial conditions**

**El Niño conditions**

**Monitoring El Ni****ñ****o**

## Slide 18

## Global Mean Sea Level Trends

**For the first time in history the global mean sea level is directly estimated from global observations.  Coupled with ocean temperature observations, the contribution of ice melting is estimated. **

**Global Mean Sea Level Trends**

**J. Willis/JPL**

**Recent rate of ice discharge from Greenland ~ 0.5 mm/year**

## Ocean Has Absorbed Most of the Heat

**J. Willis/JPL**

**Over 10 years, the heat absorbed by the ocean is enough to do one of the following:**
**heat the entire atmosphere by 5 degrees, **
**2)  melt all of the world's sea ice (3 times over), **
**3)  melt enough land-bound ice to raise sea level by 24 cm,  **

**Ocean Has Absorbed Most of the Heat**

**Net heat input from the Sun**

**Ocean heat storage**

## Chart of the Twice-Daily Lunar (M2)Tides

**Chart of the Twice-Daily Lunar (M****2****)Tides**

**Ray (1999)**

## Total tidal dissipation= 1 TW (1012 ) ~ 1/3 US energy consumption rate; half of total ocean mixing

**Egbert & Ray (2000)**

**Total tidal dissipation= 1 TW (10****12**** ) ~ 1/3 US energy consumption rate; half of total ocean mixing**

## R. Ray/GSFC

**R. Ray/GSFC**

## Ocean Mixing and the Overturning Circulation

**Sinking by gravity**

**Rising  by mixing**

**Ocean Mixing and the Overturning Circulation**

## Decadal Trends of Sea Level (1992-2005)

**cm**

**Decadal Trends of Sea Level (1992-2005)**

**13 years are not sufficient to determine a long-term trend of ocean change.**

**Ocean changes of ever-increasing time scales are being discovered**

**cm**

**Fu, Lee /JPL**

## OSTM (Ocean Surface Topography Mission)

**OSTM ****(Ocean Surface Topography Mission)**

**Exploring two decades of change in ocean climate**

## 90% of the ocean’s kinetic energy is carried by eddies which are not well resolved by a nadir-looking altimeter

**100 km**

**ground tracks of Jason (thick) and T/P (thin) Tandem Mission**

**100 km scale eddies**

**10 km scale eddies**

## A Global Hydrosphere Mapper

**A Global Hydrosphere Mapper**

**A SAR interferometry radar altimeter**

**Near-global coverage with 16-day repeat orbit**

** ****Same technique as SRTM – radar interferometry**
** ****Use of SAR to enhance the spatial resolution**
** ****1 cm measurement precision at 1 km resolution, **
**  ****superb for mapping ocean eddies**** **

##  Global warming is a fact.

** ****Its consequence to life depends on the**
**  ****ocean’s response.**
** ****Space technology is providing key  **
**   ****information on the ocean’s response.**
** ****The data stream must be continued  **
**   ****indefinitely.**
** ****New technology must be developed to fill**
**  ****key missing links in understanding **
**  ****the ocean.**