LDEOColumbia University Martinson 12 years of Palmer LTER
LDEO/Columbia University Martinson 12 years of Palmer LTER: Physical Oceanography, Spatiotemporal Variability & Ventilation of Ocean Heat Along the Western Antarctic Peninsula Douglas G. Martinson Lamont-Doherty Earth Observatory Columbia University dgm@ldeo. columbia. edu mstecker. com/pages/antsatmap. htm Photo: Dr. R. C. Smith, Sep. 2001 Martinson, 5/15/05; APCV Workshop
LDEO/Columbia University Martinson Sample region Location Map & Grid An. B. -60 A. R. COAST L. SHELF Bellingshausen Sea Ad. SLOPE Martinson, 5/15/05; APCV Workshop M. B.
LDEO/Columbia University Martinson Background SLOPE COAST SHELF SLOPE COAST Bathymetric Shading: White ≥ 750 m 750 > light-grey ≥ 450 m Dark-grey < 450 m Martinson, 5/15/05; APCV Workshop
LDEO/Columbia University Martinson Motivation Western Antarctic Peninsula § Most rapid recent regional winter warming on Earth § Major loss of perennial sea ice § 87% of glaciers are in retreat 0. 107˚ C/year Significant at 0. 05 ~5. 4 x global average Vaughan et al. , 2003 Perennial Ice Stammerjohn et al. , 2006 Martinson, 5/15/05; APCV Workshop Cook et al. , 2005
LDEO/Columbia University Martinson Source of Winter Heat 2. 13˚ 1. 70˚ ACC-core UCDW 34. 75 34. 54 PAL LTER Grid (1992 -2004) WOCE SP 04: WAP ACC (February 1992) NBP 94 -04: Bellingshausen Slope (March 1994) Source of heat Major global volumetric modes #31 #33 #51 #55 #59 ANTARCTIC (summer) SURFACE WATERS (AASW) 3. 5– 4˚C WW Martinson, 5/15/05; APCV Workshop
LDEO/Columbia University Martinson Proximity of ACC PAL LTER Sampling Grid Bellingshausen Sea Antarctic Circumpolar Current Weddell gyre SLOPE Bellingshausen Sea Amundsen Sea Ross gyre SHELF COAST Martinson, 5/15/05; APCV Workshop w. AP is unique as only location with ACC directly adjacent to shelf
LDEO/Columbia University Martinson Delivery of UCDW 1993 -2004 climatology r[z( max), Dynamic Topo] r NC – SC – OA + MA + Individual years consistent with drifter data (our only absolute velocity obs) Martinson, 5/15/05; APCV Workshop UCDW pulled onto shelf by upwelling dynamics (likely wind-driven)
LDEO/Columbia University Martinson Shelf heat flux Seasonal Cycle Fw CO 2 Uptake r, Ssummer Tsummer Biology Tf, S, rwinter CO 2, PO, etc. CO 2 Venting TD, SD, r. D CO 2 D, POD, etc. Martinson and Takahashi, in prep Martinson, 5/15/05; APCV Workshop
LDEO/Columbia University Martinson Shelf heat flux FT: Bulk Parameter vs Measured (Anz. Flux, 1994) <FTBP>W = 29. 67 Wm 2 <FTObs>W = 27. 7 Wm 2 Martinson, 5/15/05; APCV Workshop (Martinson & Iannuzzi, 1998) (Mc. Phee et al. , 1999)
LDEO/Columbia University Martinson Bulk heat flux and Entrainment/diffusive heat flux ratio W/m 2 FT Martinson, 5/15/05; APCV Workshop FET/FDT Shelf heat flux
LDEO/Columbia University Martinson 2000 Depth (db) 2001 2002 2003 Grid line Martinson, 5/15/05; APCV Workshop slope Temperature (˚C) Temperature section Depth (db) Slope (~20 km off-shelf) Temperature Q Shelf heat flux Grid line
LDEO/Columbia University Martinson 1998 Grid-wide Regime Shift (ubiquitous across physical properties) Temperature of max Equivalent ice thickness (m) Martinson, 5/15/05; APCV Workshop SDw FT variability
LDEO/Columbia University Martinson Modes of ocean heat flux Martinson, 5/15/05; APCV Workshop FT variability
Martinson Contribution to sea level rise and peninsula warming: Ocean heat flux (FT) to atmosphere over WAP shelf shows considerable change in latter part of 1900 s (coinciding with increased Tair and glacial melt): § Large step increase in 1990 (+4 Wm-2) § Qshelf & Qslope are proxies for FT § FT shows jump in 1998 by 3 Wm-2 followed by same jump each year thereafter Martinson, 5/15/05; APCV Workshop LDEO/Columbia University ocean heat flux FT variability
Conclusions: Martinson § LDEO/Columbia University WAP region dominated by circumpolar water masses o ACC/UCDW water along slope delivering heat and nutrients to WAP continental shelf o UCDW floods shelf from dynamical forcing (likely wind driven upwelling) o Slope waters enter via canyons in shelf, eventually flood onto shelf floor § WAP bathymetry controls property distributions and stratification o T–S plot shapes reflect sub-regions and indication of time since renewal § Extreme El Niño of 1998 introduced grid-wise regime shift o Apparent in all physical variables § Ocean heat flux temporal increases on shelf are consistent with strong atmospheric warming and dramatic glacial melt on WAP o Can continue increasing to what level before internal adjustments regulate? Future: § Determine WAP glacial melt and commensurate freshwater input § Secure funding for moorings to evaluate UCDW flooding episodes o Monitor excess heat supply from eddies, or other episodic flooding events and tie these events to large scale (satellite observable) mechanistic causes Martinson, 5/15/05; APCV Workshop
Martinson LDEO/Columbia University Backup slides & More Exciting PO Martinson, 5/15/05; APCV Workshop
LDEO/Columbia University Martinson Shelf heat flux m 2/s x 10 -4 ^ Grid Line (km) <Kz> Grid Station (km) Martinson, 5/15/05; APCV Workshop Grid Station (km) m 2/s x 10 -4
Martinson Salinity LDEO/Columbia University Shelf heat flux Salt Deficit (SDw) Thermal Barrier (TBw) FDT = kz cp T = TBw + SDw FET = (TBw/ )FL FL = (Fair - FDT) FT = FDT + FET (diffusive heat flux) (bulk stability) (entrainment heat flux) (latent heat flux) (total heat flux) Temperature (˚C) Martinson and Iannuzzi, JGR, 1998 Martinson, 5/15/05; APCV Workshop
LDEO/Columbia University Martinson Delivery to shelf 1993 -2004 climatology NC – SC – OA + Martinson, 5/15/05; APCV Workshop MA + r[z( max), Dynamic Topo] r
Martinson Note: water enters shelf through canyons, consistent with dynamic topo. C. Martinson, 5/15/05; APCV Workshop LDEO/Columbia University Delivery to shelf
LDEO/Columbia University Martinson Cross-shelf T-anomalies Martinson, 5/15/05; APCV Workshop Delivery to shelf
LDEO/Columbia University Martinson Lines 150 -650 (average Q-shelf) Qshelf (x 109 J/m 2) r = 0. 75 FT Wm-2 Martinson, 5/15/05; APCV Workshop FT variability
LDEO/Columbia University Martinson FT variability Qslope (x 109 J/m 2) 1990– 2004 Average Qslope = (3. 83 ± 0. 07 )x 109 ~0. 7˚ C warming of 300 m column of water below winter mixed layer (+4 W/m 2 increased FT for same Qshelf) 1930– 1989 Mean Qslope = (2. 98 ± 0. 16)x 109 rms about NUMBER OF PROFILES PER AVERAGE YEAR Martinson, 5/15/05; APCV Workshop
LDEO/Columbia University Martinson FT variability Qshelf (x 109 J/m 2) Lines 150 -650 (full shelf and coast stations) All shelf stations Year Martinson, 5/15/05; APCV Workshop
Martinson LDEO/Columbia University 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 highpressure 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. Martinson, 5/15/05; APCV Workshop
- Slides: 25