Marine Physics at SOC and BAS A look at SOC present activities and plans for the future, and avenues for possible future collaboration Sheldon Bacon, BAS, 11 March 2005 Note: from 1 May 2005, SOC becomes NOCS

Library exchanges Start sending stuff to each other!

SOC Activities and Plans Northern Polar –ARCICE project (Hawker, PhD) just finished, on Nordic Seas circulation and Fluxes –Rapid AO2 project ARTHER (Bacon PI, with Stevens, UEA, Laxon, CPOM plus international collabs.) to use tracers in OGM to determine time-varying sources of Denmark Strait Overflow Water –Next Core Strategic contains plan for Arctic Gateway hydro + carbon section, Scotland – Greenland – Canada (with Watson, UEA) Southern Polar –Drake Passage annual repeat hydro section (Williams, PhD) –Next Core Strategic contains plan for Atlantic sector Southern Ocean hydro + carbon box (with Watson, UEA)

Circulation and Fluxes in the Nordic Seas (Hawker & Bacon) Most data 1999 (Aug-Sep) Main result: most water mass conversion occurs in South box Also cruise in March 2000: led to winter flux estimate

ARTHER Objectives To determine the mechanisms responsible for generating DSOW, and to determine the variability of those mechanisms on decadal timescales, in order to better constrain its future evolution. In order to achieve this objective, we aim to determine: The degree to which high-frequency and small-scale ocean variability is under-represented in current models. The importance of sea ice mass and freshwater fluxes in the current and future evolution of DSOW. The extent to which mean and time-variant sea ice and ocean fluxes and circulation are properly represented in current models. The accuracy of current global climate model predictions of DSOW formation in the next century, and hence the evolution of the MOC.

Cruises to ? ˚N hydro (Core present + new) 24˚N moorings (RAPID + NSF) 36˚N consortium Cape Farewell (Rapid) Arctic Gateway (Core new) Southern Ocean box (Core new)

Drake Passage LCDW Salinity constant over last century Lack of variability both sides of continent Suggests Gille (2002) upper-ocean warming signal forced by atmosphere Williams, Bacon & Cunningham (2005), TBS

Collaboration Remember CPOM–UCL (tripartite collaboration in the future?) Initial (short-term) principles: –Mutually beneficial and interesting –No-cost (eg model output), low-cost (eg CASE PhDs), independently resourced (eg IPY, AFI, responsive mode proposals), in both time and money –Doable (individuals on both sides willing to sign up) Longer-term: –New SOC Core?

OCCAM at present (1) 1, 1/4 and 1/12 degree horizontal resolution 66 levels in the vertical (14 < 100 m, 29 < 500 m) KPP mixing Partial bottom boxes to resolve topography Fully interactive sea-ice model High-frequency (6-hourly) forcing Diurnal radiation cycle Also 1˚ biogeochem model North Atlantic MOC

OCCAM at present (2) Surface forcing (1985–present): –NCEP: surface air temperature, winds, sea level pressure and humidity –radiation, clouds & precip. merged from satellite products –simplified 1-D atmospheric boundary layer model plus OCCAM SST plus standard bulk formulae determine air-sea fluxes –weak relaxation in salinity currently applied to parameterise the effect of river runoff –In the presence of sea ice: use an over-ice bulk formulation –different albedos for different types of underlying surface: ocean, ice, snow, and melting ice and snow –total air-sea flux is combined from fluxes over open water and sea ice in proportion to ice concentration in model cell

Drake Passage & Scotia Sea, OCCAM 1/12˚ 2 years starting with spin-up Day-counter bottom left

OCCAM 1/4˚ Surface u-vel 2003 Annual mean

OCCAM 1/12˚ instantaneous, from December 1986

Simulated and Observed Total Ice Extent and Area

Simulated and Observed Regional Ice Extent

Simulated Ice Concentration Feb 1992Sep 2001

Observed Ice Concentration (SSMI/R) Feb 1992Sep 2001

Sea ice thickness (cm)

OCCAM Sea Ice 1985

Model Improvements Include river runoff explicitly (funded through RAPID – ARTHER, to fix Arctic) Include sub-ice-shelf circulation models (nested?) for Filchner-Ronne & Ross (+?) – Jenkins? – ‘fix’ AABW production Include seasonal land-ice melt runoff & iceberg calving Bottom boundary layer (eg Killworth) Improved bathymetry

OCCAM Scientific Projects (1) Aksenov Impact of sea ice and its variability on Southern Ocean circulation Ice–ocean interaction (eg PIG) Role of shelf boundary currents in Southern Ocean circulation variability Sea ice as a niche for Southern Ocean biological community

OCCAM Scientific Projects (2) Marsh Impact of regional climate variability on: –interbasin exchange –AAIW, AABW, Mode Water formation –and hence Southern Ocean CO 2 uptake? Is the poleward oceanic heat transport at high southern latitudes anti-correlated with the N. Atlantic MOC? –“bipolar seesaw” (Greenland cooling  West Antarctica warming)

Other stuff Ocean circulation around South Georgia –hydro data + Bernoulli inverse model + OCCAM + Argo floats Southern Ocean bathymetry Underway marine measurements –Met (cf SOC surface flux climatology), VM-ADCP, TSG etc CHIME (New, Megann) –HadCM3 atmosphere + hybrid-coordinate ocean model –Sea ice is Semtner thermodynamics + free drift

Number of Ship Reports with Sufficient Information to Estimate Latent Heat Flux per 1x1˚ Square (Climatological Monthly Average, ). Source: SOC Climatology (Josey, Kent and Taylor, 1999, J. Climate, )

CHIME: Global sea ice cover and thickness from year 100

Surface temperature errors CHIME: years mean SST error from SOC climatology HadCM3: years mean SST error from GISST climatology

Annual mean ice extent. HadCM3SSM/ICHIME year 100

Summary SOC has interests and resources in Southern Ocean and Antarctic science: BAS could help BAS has a science strategy to 2010 called Global Science in the Antarctic Context: SOC could help