# Presentation: 815429

## The Inferred 3D velocity field

- Nelson Hogg (WHOI)

**Nelson Hogg:**
- Missing PN
- Ranks with altimetry in terms of innovation and global reach

## Themes

-  Global coverage
-  Influence of bottom topography
-  Zonality of mid-depth flows
-  Presence of annual signal at mid-depths
-  Numerical models do reproduce some of these features

## Surface: Mean Meridional Velocity

*Niiler and Maximenko (personal communication)*

**Nelson Hogg:**
- Change in sign of ekman @ equator

## Surface: Mean Zonal Component

*Niiler and Maximenko (personal communication)*

**Nelson Hogg:**
- Banding in tropics
- wbcs

## Surface: Eddy Kinetic Energy

*Niiler and Maximenko (personal communication)*

*Stammer (persnonal communication)*

- Satellite

- Surface Drifters

## Kuroshio Extension:RMS eddy velocities from drifters and altimeters, and their ratio

*Niiler et al, 2002: (in press) *

- Drifter RMS

- Altimeter RMS

- Drifter / Altimeter

## Mean Surface Velocity: Kuroshio Extension

*Niiler et al, 2002: (in press)*

- Shatsky Rise

- Emperor
-  Seamounts

- Izu Ridge

## North Atlantic: Mean Surface Circulation

- North Atlantic: Mean Surface Circulation

*Fratantoni, 2001, JGR 106(10)*

**Nelson Hogg:**
- New england seamounts
- recirculations
- NAC and CGFZ

## EKE Difference: Drifter – Altimeter

*Fratantoni, 2001, JGR 106(10)*

## North Atlantic: Mean surface velocity

*Niiler and Maximenko, pers. comm.*

**Nelson Hogg:**
- New England Seamounts
- Azores C
- NAC & CGFZ
- Reykianes Ridge
- Lab Sea and offshore recirc

## “Upper level” Streamlines

*Bower et al, 2002: Nature*

*Lavender et al, 2000: Nature*

- 700m

- 

**Nelson Hogg:**
- See posters

## LSW Streamlines

*Bower et al, 2002: Nature*

- 1500m – 1750m

**Nelson Hogg:**
- CGFZ
- Split at eastern b.
- Reyk. Ridge

## Influence of Mid-Atlantic Ridge on Rafos trajectories

*Bower et al, 2002, Nature*

## AAIW: South Atlantic

*Boebel et al, 1999, GRL 26*

**Nelson Hogg:**
- Color scheme
- Eastward @ 20S

## IW (1000m) trajectories: North Pacific

*Steve Riser, pers. Comm.*

**Nelson Hogg:**
- Zonal trajectories
- Rounder streamlines

## AAIW displacements: South Pacific 

*Davis, 1998, JGR 103*

## AAIW smoothed: South Pacific

*Davis, 1998, JGR 103*

## AAIW streamlines: South Pacific

*Davis, 1998, JGR 103*

## NADW: Brazil Basin (DBE)

- RAFOS Displacements

- CLIPPER simulation

*Hogg and Owens, 1999: DSRII*

*Treguier et al, 2002: JPO*

## MAR influence?

*Treguier et al, 2002: JPO*

*Vanicek and Siedler, 2002:JPO*

- MAR influence?

_*Possible Explanations*_
*Fracture Zones: Pedlosky (JPO,31)*
*Variable mixing along MAR*
*Wind forced: Nakano and Suginohara (JPO, 32)*

## Wind forced mid-depth zonal flows

**South Atlantic**
*Clipper 1/6 degree*
*Treguier et al, 2002: JPO*

**Pacific**
*COCO 1 degree*
*Nakano and Suginahara, 2002: JPO*

**Nelson Hogg:**
- See posters

## Annual signal in South Pacific

*Davis, 1998: JGR*

## Annual signal in Brazil Basin: Least squares fit @ 2500m

- RMS residual

- U

- V

*Hogg, in prep.*

- U

- V

## Annual signal in Brazil Basin:Phase

*Hogg, in prep.*

## Annual signal in Brazil Basin:Amplitude

*Hogg, in prep.*

## Annual Signal from Clipper:Zonal Velocity

*Thierry and Teguier, pers. Comm.*

- Amplitude (cm/s)

- Phase (months)

## Beta dispersion

*Hogg, in prep.*

## Application to inverse calculations

- Pacifiic: 32S

*Wijffels et al, 2001: JPO*

## Total: 1784 floats, 4300 float years

## Nelson Hogg:

**Nelson Hogg:**
- 3650 = 1 float continuous for 10 yr

## Summary

- Float/drifter program has been a remarkable success and should be considered one of WOCE's crown jewels
- Much of the information is only semi-quantitative at best: *more drifters of longer duration needed*
- Use in constraining inverse models still in infancy: *should be encouraged*

**Nelson Hogg:**
- Davis poster