Climatological-scale science Climatological-scale science from sparse datafrom sparse data

Michael Steele & Wendy ErmoldPolar Science Center / Applied Physics Laboratory / University of Washington,

Seattle WA USA

Kara Sea

# of

pro

files

Michael SteelePolar Science Center / APLUniversity of Washington

http://psc.apl.washington.edu

Septembersea ice cover

1979

2003

N. PoleN. Pole

N. PoleN. Pole

N. AmericaN. America

RussiaRussia

RussiaRussia

N. AmericaN. America

Example: A study of Arctic Ocean surface warming over the past 100 years

How much ocean warming?

WOD’05WOD’05data distribution,data distribution,

colored by: colored by:

Temperature (ºC)

Years

TemperatureTemperature

Earliest YearEarliest Year

50N – 90N0-10 m

July, Aug, Sept

Temperature (ºC)

TemperatureTemperatureData Handling details:

1. ACQUIRE THE DATAThe data were downloaded off the web as “wrapped” ascii files:

World Ocean Database, 2005http://www.nodc.noaa.gov/OC5/WOD05/pr_wod05.html

2. REFORMATINGData were reformatted into the following ascii columns:

Profile_ID# latitude longitude depth temperature salinity month year

Instrument Counts for some Arctic shelves

Drifting Buoy Data mechanical bathythermograph data

ocean station data: bottle, low res CTD eXpendable bathythermograph data

Raw data histograms

Temporal BiasTemporal Bias

SPATIAL BIASSPATIAL BIAS

Mean SST = 2.2 C Mean SST = 1.9 C

Example: East Siberian + eastern Laptev Seas

Temperature (ºC)

Raw Data 50km bin averaged

dense dense WARMWARM profiles profiles

sparse sparse COLDCOLD profiles profiles

Fake trendsFake trends

cold

warmer

hot

Year 1 Year 2 Year 3

datadata

Steady state ocean + spatially biased sampling fake warming trend!

The solution: Multiple Regression

T = a + bx + cy + dPHC(x,y) + eyear

spatial fieldspatial field

Anomalies are defined relative to the mean spatial field over a given time period.

…no “intra-year” predictor

^

Long-term N/AO trendsLong-term N/AO trends

Are these trends reflected in the SST data?Are these trends reflected in the SST data?

°C per decade

(a)SST:1930-1965

(b) SST:1965-1995

(c) SST:1930-1995

(d) OHC:1965-1995

MJ/m2 per decade

-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5

-100 -80 -60 -40 -20 0 20 40 60 80 100

SST trend

OHC trend

No M.R. here:just smoothed, 300 km binned trends

(a) Beaufort-E (b) Beaufort-W

(c) Bering (d) ESS+Laptev

(e) Kara (f) Barents

SST anomalies using M.R.SST anomalies using M.R.Ice thickness (m

)