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Use of radium isotopes to estimate mixing rates and trace sediment inputs to surface waters in northern Marguerite Bay, Antarctic Peninsula

Use of radium isotopes to estimate mixing rates and trace sediment inputs to surface waters in northern Marguerite Bay, Antarctic Peninsula
Use of radium isotopes to estimate mixing rates and trace sediment inputs to surface waters in northern Marguerite Bay, Antarctic Peninsula

In the western Antarctic Peninsula region, micronutrient injection facilitates strong plankton blooms that support productive food webs, unlike large areas of the low-productivity Southern Ocean. We use naturally occurring radioisotopes of radium to constrain rates of chemical fluxes into Ryder Bay (a small coastal embayment in northern Marguerite Bay), and hence to evaluate possible sources of sediment-derived micronutrients and estimate sediment-ocean mixing rates. We present the first coupled, short-lived radium isotope ( 223Ra and 224Ra) measurements from Antarctic waters, both present at very low activities (mean 0.155 and 3.21 dpm m-3, respectively), indicating much lower radium inputs than in other coastal environments. Longer-lived 228Ra activity was also lower than existing nearshore values, but higher than open ocean waters, indicating some degree of coastal radium input on timescales exceeding the week-to-month range reflected by 223Ra and 224Ra. Using a simple diffusion model along a shore to mid-bay transect, effective horizontal eddy diffusivity estimates ranged from 0.22-0.83 m2 s-1 from 223Ra and 224Ra, respectively, much lower than already-low mixing estimates for the Southern Ocean. Significant radium enrichment and much faster mixing (18 m2 s-1) was found near a marine-terminating glacier and consequently any sediment-derived micronutrient inputs in this location are more probably dominated by glacial processes than groundwater, land runoff, or marine sediment sources.

actinium-227, glacial inputs, horizontal eddy diffusivity, land-ocean interface, Radium Delayed Coincidence Counter (RaDeCC), Ryder Bay
0954-1020
445-456
Annett, Amber L.
de404d72-7e90-4dbd-884a-1df813808276
Henley, Sian F.
cd7c7f77-8494-46ad-98a9-08907fa6e06b
Van Beek, Pieter
1a0b89c0-4695-4268-9cc0-31a1d322b063
Souhaut, Marc
ec8988b8-8b4f-440c-aa6d-2ee86ef80b74
Ganeshram, Raja
108fdc69-5502-4b6f-922f-dd12b398e267
Venables, Hugh J.
ed72170e-cf1b-4b38-b5e8-d3eed65cdb06
Meredith, Michael P.
25fd5f1c-f3ed-40a2-af59-5a7074a25fcd
Geibert, Walter
c3679aba-8aab-40ec-ae0e-2112a4c6d471
Annett, Amber L.
de404d72-7e90-4dbd-884a-1df813808276
Henley, Sian F.
cd7c7f77-8494-46ad-98a9-08907fa6e06b
Van Beek, Pieter
1a0b89c0-4695-4268-9cc0-31a1d322b063
Souhaut, Marc
ec8988b8-8b4f-440c-aa6d-2ee86ef80b74
Ganeshram, Raja
108fdc69-5502-4b6f-922f-dd12b398e267
Venables, Hugh J.
ed72170e-cf1b-4b38-b5e8-d3eed65cdb06
Meredith, Michael P.
25fd5f1c-f3ed-40a2-af59-5a7074a25fcd
Geibert, Walter
c3679aba-8aab-40ec-ae0e-2112a4c6d471

Annett, Amber L., Henley, Sian F., Van Beek, Pieter, Souhaut, Marc, Ganeshram, Raja, Venables, Hugh J., Meredith, Michael P. and Geibert, Walter (2013) Use of radium isotopes to estimate mixing rates and trace sediment inputs to surface waters in northern Marguerite Bay, Antarctic Peninsula. Antarctic Science, 25 (3), 445-456. (doi:10.1017/S0954102012000892).

Record type: Article

Abstract

In the western Antarctic Peninsula region, micronutrient injection facilitates strong plankton blooms that support productive food webs, unlike large areas of the low-productivity Southern Ocean. We use naturally occurring radioisotopes of radium to constrain rates of chemical fluxes into Ryder Bay (a small coastal embayment in northern Marguerite Bay), and hence to evaluate possible sources of sediment-derived micronutrients and estimate sediment-ocean mixing rates. We present the first coupled, short-lived radium isotope ( 223Ra and 224Ra) measurements from Antarctic waters, both present at very low activities (mean 0.155 and 3.21 dpm m-3, respectively), indicating much lower radium inputs than in other coastal environments. Longer-lived 228Ra activity was also lower than existing nearshore values, but higher than open ocean waters, indicating some degree of coastal radium input on timescales exceeding the week-to-month range reflected by 223Ra and 224Ra. Using a simple diffusion model along a shore to mid-bay transect, effective horizontal eddy diffusivity estimates ranged from 0.22-0.83 m2 s-1 from 223Ra and 224Ra, respectively, much lower than already-low mixing estimates for the Southern Ocean. Significant radium enrichment and much faster mixing (18 m2 s-1) was found near a marine-terminating glacier and consequently any sediment-derived micronutrient inputs in this location are more probably dominated by glacial processes than groundwater, land runoff, or marine sediment sources.

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More information

e-pub ahead of print date: 29 October 2012
Published date: June 2013
Keywords: actinium-227, glacial inputs, horizontal eddy diffusivity, land-ocean interface, Radium Delayed Coincidence Counter (RaDeCC), Ryder Bay

Identifiers

Local EPrints ID: 418606
URI: https://eprints.soton.ac.uk/id/eprint/418606
ISSN: 0954-1020
PURE UUID: b170837a-904b-4c3d-9c7b-a276b0fb8f5d
ORCID for Amber L. Annett: ORCID iD orcid.org/0000-0002-3730-2438

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Date deposited: 12 Mar 2018 17:30
Last modified: 14 Mar 2019 01:25

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Contributors

Author: Amber L. Annett ORCID iD
Author: Sian F. Henley
Author: Pieter Van Beek
Author: Marc Souhaut
Author: Raja Ganeshram
Author: Hugh J. Venables
Author: Michael P. Meredith
Author: Walter Geibert

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