Douglas G. Martinson Lamont-Doherty Earth Observatory Columbia University 12 years of Palmer LTER: Physical Oceanography, Spatiotemporal Variability & Ventilation of Ocean Heat Along the Western Antarctic Peninsula Photo: Dr. R.C. Smith, Sep mstecker.com/pages/antsatmap.htm Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop

Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop Location Map & Grid Bellingshausen Sea An. Ad. B. A. R. L. M.B. SLOPE SHELF COAST Sample region

Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop SHELF SLOPE COAST SLOPE SHELF COAST Bathymetric Shading: White ≥ 750 m 750 > light-grey ≥450 m Dark-grey < 450 m Background

Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop Roadmap:  MOTIVATION: Antarctic Peninsula shows Earth's greatest rapid (winter) regional warming.  Evidence shows impact of most rapid regional winter warming on Earth — increased air temperature and dramatic loss of sea and glacial ice  What is source of heat to region?  Stammerjohn (2006) implicates changes in large scale climate patterns (ENSO and SAM) coincide to alter surface ice conditions, allowing more effective ventilation of ocean heat (only significant source of heat in winter)  I will focus solely on this ocean heat, which occurs in Upper Circumpolar Deep Water (UCDW)  What is proximity of heat to region?  Antarctic Circumpolar Current (ACC) delivers warm UCDW directly to wAP continental shelf (to the front door); unique to this region in the Antarctic  What is delivery of heat to continental shelf?  ACC floods shelf (uplifted to shelf depths by ACC dynamics), and then onto shelf by regional surface forcing driving upwelling  What is ocean heat flux and how has it changed through time?  Increases after 1980s, and makes another jump followed by trend in 1998

Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop 0.107˚ C/year Significant at 0.05 ~5.4x global average Perennial Ice Western Antarctic Peninsula  Most rapid recent regional winter warming on Earth  Major loss of perennial sea ice  87% of glaciers are in retreat Motivation Vaughan et al., 2003 Stammerjohn et al., 2006Cook et al., 2005

Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop 1.70˚ 2.13˚ Source of Winter Heat ACC-core UCDW ANTARCTIC (summer) SURFACE WATERS (AASW) WW PAL LTER Grid ( ) WOCE SP04: WAP ACC (February 1992) NBP94-04: Bellingshausen Slope (March 1994) Major global volumetric modes #31 #33 #51 #55 #59 Source of heat 3.5–4˚C

Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop Bellingshausen Sea Amundsen Sea Weddell gyre Ross gyre Bellingshausen Sea PAL LTER Sampling Grid Proximity of ACC wAP is unique as only location with ACC directly adjacent to shelf SLOPE SHELF COAST Antarctic Circumpolar Current

Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop r SC – MA + OA + NC – climatologyr[z(  max ), Dynamic Topo] Delivery of UCDW UCDW pulled onto shelf by upwelling dynamics (likely wind-driven) Individual years consistent with drifter data (our only absolute velocity obs)

Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop Seasonal Cycle Martinson and Takahashi, in prep CO2 D, PO D, etc. T D, S D,  D CO2 Venting CO2, PO, etc. T f, S,  winter Biology F CO2 D, PO D, etc. T D, S D,  D T summer CO2 Uptake S summer ,, w CO2, PO, etc. T f, S,  winter Shelf heat flux

Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop F T : Bulk Parameter vs Measured (AnzFlux, 1994) W = Wm 2 (Martinson & Iannuzzi, 1998) W = 27.7 Wm 2 (McPhee et al., 1999) Shelf heat flux

Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop Bulk heat flux and Entrainment/diffusive heat flux ratio F ET /F DT FTFT W/m 2 Shelf heat flux

Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop Slope (~20 km off-shelf) Temperature Grid line Depth (db) Temperature (˚C) Q slope Shelf heat flux Temperature section

Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop 1998 Grid-wide Regime Shift (ubiquitous across physical properties) Temperature of  max Equivalent ice thickness (m) SD w F T variability

Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop Modes of ocean heat flux F T variability

Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop Ocean heat flux (F T ) to atmosphere over WAP shelf shows considerable change in latter part of 1900s (coinciding with increased T air and glacial melt):  Large step increase in 1990 (+4 Wm -2 )  Q shelf & Q slope are proxies for F T  F T shows jump in 1998 by 3 Wm -2 followed by same jump each year thereafter Contribution to sea level rise and peninsula warming: ocean heat flux F T variability

Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop  WAP region dominated by circumpolar water masses oACC/UCDW water along slope delivering heat and nutrients to WAP continental shelf oUCDW floods shelf from dynamical forcing (likely wind driven upwelling) oSlope waters enter via canyons in shelf, eventually flood onto shelf floor  WAP bathymetry controls property distributions and stratification oT–S plot shapes reflect sub-regions and indication of time since renewal  Extreme El Niño of 1998 introduced grid-wise regime shift oApparent in all physical variables  Ocean heat flux temporal increases on shelf are consistent with strong atmospheric warming and dramatic glacial melt on WAP oCan continue increasing to what level before internal adjustments regulate? Conclusions: Future:  Determine WAP glacial melt and commensurate freshwater input  Secure funding for moorings to evaluate UCDW flooding episodes oMonitor excess heat supply from eddies, or other episodic flooding events and tie these events to large scale (satellite observable) mechanistic causes

Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop Backup slides & More Exciting PO

Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop m 2 /s x10 -4 Grid Line (km) Grid Station (km) m 2 /s x10 -4  ^ Shelf heat flux

Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop F DT = k z  c p  T(diffusive heat flux)  = TB w + SD w (bulk stability) F ET = (TB w /  F L (entrainment heat flux) F L = (F air - F DT  (latent heat flux) F T = F DT + F ET (total heat flux) Salinity Temperature (˚C) Thermal Barrier (TB w ) Salt Deficit (SD w ) Martinson and Iannuzzi, JGR, 1998 Shelf heat flux

Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop r SC – MA + OA + NC – climatologyr[z(  max ), Dynamic Topo] Delivery to shelf

Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop C. Delivery to shelf Note: water enters shelf through canyons, consistent with dynamic topo.

Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop Cross-shelf T-anomalies Delivery to shelf

Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop F T Wm -2 Q shelf (x10 9 J/m 2 ) Lines (average Q-shelf) r = 0.75 F T variability

Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop YEAR 1990–2004 Average Q slope = (3.83 ± 0.07 )x –1989 Mean Q slope = (2.98 ± 0.16)x10 9 ~0.7˚ C warming of 300 m column of water below winter mixed layer (+4 W/m 2 increased F T for same  Q shelf ) Q slope (x10 9 J/m 2 ) NUMBER OF PROFILES PER AVERAGE F T variability  rms about 

Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop Year Lines (full shelf and coast stations) Q shelf (x10 9 J/m 2 ) All shelf stations F T variability

Martinson LDEO/Columbia University Martinson, 5/15/05; APCV Workshop The Antarctic Dipole (of which Palmer Station lies at the node point), is the largest response to ENSO events outside of the tropics, displaying a strong tropical-polar teleconnection. It is a major Southern Ocean polar climate mode. It shows a dipole whereby during an El Niño the Weddell gyre is spun up, and becomes colder with more sea ice, while the Amundsen Sea shows the opposite. For La Niña, the opposite relationship is seen. Two mechanisms are responsible for the formation & maintenance of the Antarctic Dipole: (1) heat fluxes due to the mean meridional circulation of regional Ferrel Cell and (2) anomalous high- pressure center generated by stationary eddies. The changes in the Hadley Cell, the jet stream, and the Rossby Wave train, all associated with El Niño, link the tropical forcing to these high latitude processes.