1 of 18

Ciara Pimm (ciara.pimm@whoi.edu)¹, Michael Spall¹

¹Woods Hole Oceanographic Institution

Water mass transformation in an idealised model of the East Greenland Current

Introduction

Strand, E., Bagøien, E., Edwards, M., Broms, C. and Klevjer, T., 2020. Spatial distributions and seasonality of four Calanus species in the Northeast Atlantic. Progress in Oceanography, 185, p.102344.

Hi, I’m Ciara Pimm, I’m a postdoc in Physical Oceanography and I’ve been here for about 7 months. So today I am going to talk about the idealised modelling I have been doing since I started here. First, I am going to introduce the Nordic sea region, its currents and watermasses, then I will focus on the East Greenland current and why it is important. Then, I will explain the model setup, and how it is initialised and forced. Then we will go into some preliminary results. So, firstly let’s just set the scene of the Nordic Sea. The Nordic Sea is made up of the Greenland Sea, the Norwegian Sea, and the Iceland Sea. Fram strait to the north connects the Nordic Sea to the Arctic and cold water and ice flows into the Nordic Sea through this passage. Denmark Strait to the south is a region for outflow into the Arctic.

2 of 18

Water mass transformation in an idealised model of the East Greenland Current

Introduction: Water masses

Latarius, K. and Quadfasel, D., 2016. Water mass transformation in the deep basins of the Nordic Seas: Analyses of heat and freshwater budgets. Deep Sea Research Part I: Oceanographic Research Papers, 114, pp.23-42.

3 of 18

Water mass transformation in an idealised model of the East Greenland Current

Introduction: Sea Ice Concentration

Våge, K., Papritz, L., Håvik, L., Spall, M.A. and Moore, G.W.K., 2018. Ocean convection linked to the recent ice edge retreat along east Greenland. Nature communications, 9(1), p.1287.

As we have seen the Nordic Seas are a key region for the global-scale thermohaline overturning circulation. And they are also an export pathway for large amounts of freshwater. In a warming climate ice melt and river runoff at high latitudes will also increase, with the Arctic and Nordic regions warming more than the global average. Sea ice along the east coast of Greenland has been in dramatic decline for at least 50 years. Here we can see that ice edge has been retreating over time. The dashed lines along the Greenland shelf represent the mean 50% sea ice concentrationcontours from winter (Jan–Mar) 2016 (white) and decadal means from 1980–1989 (red), 1990–1999 (orange), and 2000–2009 (yellow). The ice edge retreat has been shown to alter air-sea exchange and extent of deep convection in the basin interiors, which influences water mass transformation. So this is why we are interested in studying this topic and understanding how this region may change in the future.

4 of 18

Water mass transformation in an idealised model of the East Greenland Current

Model Setup: Grid

Boundary

Shelfbreak

Interior

5 of 18

Water mass transformation in an idealised model of the East Greenland Current

Model Setup: Initial Conditions

Potential Temperature

Salinity

Sea Surface Height

Meridional

Velocity

6 of 18

Water mass transformation in an idealised model of the East Greenland Current

Model Setup: Forcing

Air Temperature

Radiation

Winds

Black - north, Red – south

Dashed – ERA5, Solid - Idealised

7 of 18

Water mass transformation in an idealised model of the East Greenland Current

Results: Transformation of density layers

Density layers entering region from north

Density layers exiting region from south

Density layers entering/exiting region at edge of boundary

8 of 18

Water mass transformation in an idealised model of the East Greenland Current

Results: Transformation of density layers

Water mass transformation is calculated using import from north and east, and export from south and east.
Dense water is produced over the shelf.
This is compensated for by a loss of lighter water masses.

9 of 18

Next Steps: More realistic East Greenland Current model

Topography

Water mass transformation in an idealised model of the East Greenland Current

Idealised

‘Realistic’

10 of 18

(North of domain, in January)

Next Steps: More realistic East Greenland Current model

Water mass transformation in an idealised model of the East Greenland Current

Initial Conditions: Potential Temperature

Idealised

‘Realistic’

11 of 18

Next Steps: More realistic East Greenland Current model

Water mass transformation in an idealised model of the East Greenland Current

Initial Conditions: Salinity

Idealised

‘Realistic’

(North of domain, in January)

12 of 18

Next Steps: More realistic East Greenland Current model

Water mass transformation in an idealised model of the East Greenland Current

Initial Conditions: Zonal Velocity

No zonal velocities

Idealised

‘Realistic’

(North of domain, in January)

13 of 18

Next Steps: More realistic East Greenland Current model

Water mass transformation in an idealised model of the East Greenland Current

Initial Conditions: Meridional Velocity

Idealised

‘Realistic’

(North of domain, in January)

14 of 18

Next Steps: More realistic East Greenland Current model

Water mass transformation in an idealised model of the East Greenland Current

Initial Conditions: Sea Surface Height

Idealised

‘Realistic’

(In January)

15 of 18

Next Steps: More realistic East Greenland Current model

Water mass transformation in an idealised model of the East Greenland Current

Forcing: Air Temperature

Idealised

‘Realistic’

16 of 18

Next Steps: More realistic East Greenland Current model

Water mass transformation in an idealised model of the East Greenland Current

Forcing: Radiation

Idealised

‘Realistic’

shortwave

longwave

17 of 18

Next Steps: More realistic East Greenland Current model

Water mass transformation in an idealised model of the East Greenland Current

Forcing: Winds

Idealised

‘Realistic’

zonal

No zonal velocities

meridional

18 of 18

We will use this model setup to find where water mass transformation is taking place, i.e., over the shelf, over open ocean, in ice covered, or ice free regions.
Identify hotspots of this water mass transformation and exchange.
Look at how these processes change over different climate forcing scenarios, i.e., warming air temperature, less ice input, etc.

Water mass transformation in an idealised model of the East Greenland Current

Further Work

Questions?