1 of 51

Upstream pathways of the Faroe Overflow (UFO)

A collaborative program to study the dense water pathways feeding the Faroe Bank Channel overflow

Robert S. Pickart

Woods Hole Oceanographic Institution

2 of 51

​

1. Motivation for the UFO program

​

2. Overview of the 2024 cruises; some initial findings/questions

​

3. Tentative plans for the 2025 field season

​

Outline

3 of 51

The North Atlantic Meridional Overturning Circulation (AMOC)

4 of 51

The North Atlantic Meridional Overturning Circulation (AMOC)

​

Region of warm to

cold conversion

​

Denmark

Strait

Faroe Bank

Channel

5 of 51

The North Atlantic Meridional Overturning Circulation (AMOC)

EGC

6 of 51

The North Atlantic Meridional Overturning Circulation (AMOC)

EGC

NIJ

7 of 51

The North Atlantic Meridional Overturning Circulation (AMOC)

EGC

NIJ

IFSJ

8 of 51

Iceland-Faroe Slope Jet (IFSJ)

Semper et al. (2020)

Transport of dense water: two branches

vertical structure of IFSJ: bottom intensified

9 of 51

Huang et al. (2020)

Map of comparing upstream water properties to the two overflows

DS

FBC

600-650m layer

Arctic-origin water

10 of 51

Circulation schematic of the Nordic Seas

From the UFO proposal

11 of 51

Main Hypothesis of UFO

The Iceland-Faroe Slope Jet (IFSJ) is the dominant contributor to the Faroe Bank Channel Overflow, carrying dense water

mainly formed in the Greenland Sea and brought southward by topographically steered pathways that connect to the IFSJ.

Collaborative approach:

Fieldwork + Modeling

WHOI, FAMRI, UIB, MFRI

12 of 51

2024 fieldwork

R/V Armstrong

Photo by Hannah

13 of 51

UFO Mooring array

WHOI

UIB

FAMRI

UIB glider line

Photo by Marina

14 of 51

  • Seaglider sg563 deployed Aug 2024

​

​

  • 2 occupations of UFO1-UFO8 transect

​

  • 31 occupations of UFO8-Sta25 transect

​

​

  • 2 out of 31 occurred after 15 Feb 2025

​

  • Reduced sampling since 15 Feb to conserve energy. Large roll (and corrections) has used more energy than normal

​

  • Planned recovery mid-May 2025 on

R/V Jákup Sverri cruise

​

  • Sg563 will then be replaced by a new glider (Slocum w/ rechargeable batteries) that will operate along the transect until the next UFO cruise (Aug 2025)

UFO glider

from A. Brackstad

UFO glider

UFO1

STA 25

UFO10

UFO8

UFO9

15 of 51

UFO mooring array

color = temperature (∘C)

contours = density (kg m-3)

16 of 51

color = temperature

contours = density

color = velocity

contours = density

Section FR

1

2

3

Faroe

Current

Three deep branches

17 of 51

Section FR

Section FRR

color = temperature

contours = density

color = velocity

contours = density

1

2

3

1

2

3

Faroe

Current

Faroe

Current

Three deep branches

Three deep branches

18 of 51

UFO three-ship survey

14 August – 26 September 2024

19 of 51

What did we learn about

the upstream pathways?

Photo by Tyler

20 of 51

Section KR

Section LE

21 of 51

Section KR

Section LE

color = temperature

contours = density

color = velocity

contours = density

1

2

3

22 of 51

Section KR

Section LE

color = temperature

contours = density

color = velocity

contours = density

1

2

3

1

2

3

23 of 51

Section SFZ

24 of 51

Section SFZ

color = temperature

contours = density

color = velocity

contours = density

1

EIC

25 of 51

Section SFZ

color = temperature

contours = density

1

EIC

1

EIC

Occupation from 2011

26 of 51

Section SFZ

color = temperature

contours = density

color = velocity

contours = density

1

EIC

27 of 51

Section IS

28 of 51

Section IS

color = temperature

contours = density

color = velocity

contours = density

2

1

29 of 51

Section GSS

30 of 51

Section GSS

2

2

3

Norwegian Atl

Current

31 of 51

Section JMW

Section JME

32 of 51

Section JMW

2

3

33 of 51

Section JME

Section JMW

2

3

3

34 of 51

Section JMR

35 of 51

3

Section JMR

Norwegian Atl

Current

36 of 51

What did we learn about

the upstream pathways?

37 of 51

What did we learn about

the upstream pathways?

3

2

1

38 of 51

3

2

1

Some outstanding questions:

  • Can the flow stemming from the Mohn Ridge jump the O(20km) gap

of the Jan Mayen Channel, or does it enter the channel and recirculate?

​

39 of 51

3

2

1

Some outstanding questions:

  • Can the flow stemming from the Mohn Ridge jump the O(20km) gap

of the Jan Mayen Channel, or does it enter the channel and recirculate?

​

  • Does flow from the Jan Mayen Channel (or western side of the Mohn Ridge)

get to the Kolbeinsey Ridge?

​

40 of 51

3

2

1

Some outstanding questions:

  • Can the flow stemming from the Mohn Ridge jump the O(20km) gap

of the Jan Mayen Channel, or does it enter the channel and recirculate?

​

  • Does flow from the Jan Mayen Channel (or western side of the Mohn Ridge)

get to the Kolbeinsey Ridge?

​

  • What is the origin of the dense flow entering the Spar Fracture Zone?

Does it get pulled off the east Greenland slope along with the EIC, or does

it recirculate at Denmark Strait to flow northward before entering

the fracture zone?

​

41 of 51

3

2

1

Some outstanding questions:

  • Can the flow stemming from the Mohn Ridge jump the O(20km) gap

of the Jan Mayen Channel, or does it enter the channel and recirculate?

​

  • Does flow from the Jan Mayen Channel (or western side of the Mohn Ridge)

get to the Kolbeinsey Ridge?

​

  • What is the origin of the dense flow entering the Spar Fracture Zone?

Does it get pulled off the east Greenland slope along with the EIC, or does

it recirculate at Denmark Strait to flow northward before entering

the fracture zone?

​

  • How can the dense water from the two deepest branches contribute to

the FBCO which has a sill depth of 800 m?

​

42 of 51

What’s happening to the dense water?

43 of 51

Section SFZ 2024

color = temperature

contours = density

Spar Fracture Zone section 2024

44 of 51

Section SFZ 2024

Section SFZ 2011

color = temperature

contours = density

Spar Fracture Zone section 2024

Spar Fracture Zone section 2011

45 of 51

color = temperature

contours = density

Section KR 2024

Krossanes section 2024

46 of 51

color = temperature

contours = density

Section KR 2024

Section KR 2011

Krossanes section 2024

Krossanes section 2011

47 of 51

Time history of water in the Greenland Sea over the past 70 years

From Anna-Marie Strehl

48 of 51

Time history of water in the Greenland Sea over the past 70 years

Outstanding question:

  • Can we track the propagation of this density signal southward

using the historical data and/or reanalysis fields?

From Anna-Marie Strehl

49 of 51

R/V Revelle

2025 UFO fieldwork

50 of 51

Leg 1: 15 Aug – 25 Aug

51 of 51

Leg 2: 25 Aug – 18 Sep