Research Projects
We study the natural variations that occurred in Earth's climate in the pre-industrial age, with a focus on the tropics, the heat engine of the climate system. This provides a baseline against which more recent changes caused by human activities can be assessed. Because satellites, thermometers, rain gauges and and the like did not exist or were not widely used prior to the start of the Industrial Age about 150 years ago we must develop indirect means to reconstruct the climate of that time.
Our lab specializes in developing a relatively new class of climate proxies based on the hydrogen and carbon isotope ratios of molecular fossils left behind by microalgae and mangroves. We put much effort into testing and calibrating these new measures of rainfall and salinity by growing phytoplankton cultures and mangrove trees under controlled conditions in our lab so that we can estimate these parameters in the past with precision.
- Tropical Climate & Hydrology
Since the Last Glacial Maximum
- Tropical Pacific climate
changes during the last 2,000 years
- Holocene changes in the
Intertropical Convergence Zone (ITCZ)
- Paleohydrologic reconstructions
from molecular & isotopic changes in tropical Pacific lake, bog
& ocean sediments
- El Ni_o-Southern Oscillation
variations since the last glacial maximum
- SST reconstructions from
alkenones in Eastern Equatorial Pacific sediments
- Galapagos
2004 - El Junco Lake, San Cristobal Island
- Galapagos 2008 -
Isabela & Floreana Lakes & Lagoons
- Christmas
(Kiritimati) & Washington (Teraina) Islands 2005
- Palau 2004
- Panama Basin 2005
- Clipperton
Atoll 2008
- Marshall
Islands 2009
- Kosrae, FSM 2009
- Nauru
2010
- Brisbane
River 2010
- Kosrae 2010
- Wallis
& Futuna 2011
- Fiji 2011
- Solomon Islands 2011
- Kosrae 2011
- Yap, Chuuk, Pohnpei
& Guam 2012
- Palau 2013
- Hainan Island, China 2016
- Galapagos 2016
- Palau 2016
- Carré, Sachs, Purca, Schauer, Braconnot, Falcón, Julien, Lavallée (2014) "“Holocene history of ENSO variance and asymmetry in the eastern tropical Pacific”. Science. Published online Aug. 7, 2014.
- Zhang, Leduc, Sachs (2014) "“El Niño evolution during the Holocene revealed by a biomarker rain gauge in the Galápagos Islands”. Earth & Planetary Science Letters In press.
- Atwood & Sachs (2014) "“Separating ITCZ- and ENSO-related rainfall changes in the Galápagos over the last 3 kyr using D/H ratios of multiple lipid biomarkers”. Earth & Planetary Science Letters In press.
- Timmermann, Sachs, Timm (2014) "“Assessing divergent SST behavior during the last 21 ka derived from alkenones and G. ruber-Mg/Ca in the equatorial Pacific”. Paleoceanography Vol. 29: 680-696.
- Sichrowsky, Schabetsberger, Sonntag, Stoyneva, Maloney, Nelson, Richey, Sachs (2014) "“Limnological characterization of volcanic crater lakes on Uvea Island (Wallis and Futuna, South Pacific)”. Pacific Science Vol. 68: 333-343.
- Myhrvold, Janny, Nelson, Ladd, Atwood, Sachs (2014) "Holocene Closure of Lib Pond, Marshall Islands." PLoS ONE Vol. 9(3): e90939.
- Collins, Bush, Sachs (2013) "Microrefugia and species persistence in the Galápagos highlands: a 26,000-year paleoecological perspective." Frontiers in Genetics Vol. 4.
- Leduc, Sachs, Kawka, Schneider (2013) "Holocene changes in eastern equatorial Atlantic salinity as estimated
by water isotopologues." Earth and Planetary Science Letters Vol. 362: 151-162.
- Carre, Azzoug, Bentaleb, Chase, Fontugne, Jackson,
Ledru, Maldonado, Sachs, Schauer (2012) Mid-Holocene mean
climate in the south eastern Pacific and its influence on South
America. Quaternary International Vol. 253: 55-66.
- Smittenberg, Saenger, Dawson, Sachs (2011) "Compound-specific D/H ratios of the marine lakes of Palau as proxies for West Pacific
Warm Pool hydrologic variability." Quaternary
Science Reviews Vol. 30: 921-933.
- Sachs & Myhrvold (2011) "A shifting band of
rain." Scientific American Vol. 304:
60-65.
- Zhang, Metzger, Sachs (2011) "Co-occurrence
of long chain diols, keto-ols, hydroxy acids and keto acids in recent
sediments of Lake El Junco, Galapagos Islands." Organic
Geochemistry Vol. 42: 823-837.
- Sachs & Ladd (2010) "Climate
and oceanography of the Galapagos in the 21st century: expected
changes and research needs." Galapagos Research Vol.
67: 50-54.
- Sachs, Sachse, Smittenberg, Zhang, Battisti,
Golubic (2009) "Southward
movement of the Pacific intertropical convergence zone AD 1400-1850."
Nature Geoscience, 2(7): 519-525.
- Koutavas & Sachs (2008) Northern
timing of deglaciation in the eastern equatorial Pacific from alkenone
paleothermometry, Paleoceanography Vol. 23: PA4205,
doi:10.1029/2008PA001593.
- Sachse & Sachs (2008) Inverse
relationship between D/H fractionation in cyanobacterial lipids and salinity
in Christmas Island saline ponds. Geochimica
et Cosmochimica Acta Vol.72: 793-806.
- Pahnke,
Sachs, Keigwin, Timmermann, Xie (2007) Eastern
tropical Pacific hydrologic changes during the past 27,000 years from
D/H ratios in alkenones, Paleoceanography Vol. 22, PA4214,
doi:10.1029/2007PA001468.
- Smittenberg & Sachs (2007) Purification
of dinosterol for hydrogen isotopic analysis using high-performance
liquid chromatography–mass spectrometry Journal of
Chromatography A Vol. 1169: 70-76.
- Zhang, Metzger & Sachs (2007) Biomarker
evidence for the co-occurrence of three races (A, B and L) of
Botryococcus braunii in El Junco Lake, Gal_pagos, Organic
Geochemistry Vol. 38: 1459-1478.
- Saenger, Smittenberg, Miller, Sachs (2006) A Physico-chemical
survey of inland lakes and saline ponds: Christmas Island (Kiritimati)
and Washington (Teraina) Islands, Republic of Kiribati Saline
Systems Vol. 2(1): 8
- Sachs
& Smittenberg (2005) Reconstructing the History of El Ni_o
from Galapagos Lakes EAPSpeaks, MIT-EAPS Newsletter Vol.
1(1).
- Koutavas, Lynch-Stieglitz,
Marchitto, Sachs (2002) "El
Ni_o–like pattern in Ice Age tropical Pacific sea surface temperature."
Science Vol. 297: 226-230.
- Hydrogen and carbon isotopes in
algal & plant lipids and their application to paleoclimatology
- Phytoplankton Continuous cultures
We are growing mangroves in order to quantify the hydrogen and carbon isotope
fractionation during lipid synthesis across a range of salinities. This
research was motivated by graduate student Nemiah Ladd's observation that hydrogen isotope ratios in
lipids from the leaves of the gray mangrove, Avicennia marina,
decreased as salinity increased in the Brisbane River
(SE Queensland, Australia). This is opposite the fractionation response
observed in phytoplankton, whose lipids are characterized by an increase in
their deuterium-to-hydrogen ratio as salinity increases (see our studies from
Christmas Island
and the Chesapeake Bay).
We would like to quantify this response with controlled experiments
with a variety of mangrove species so that we can calibrate a paleosalinity
proxy from mangrove lipids in sediment cores. These experiments are
being performed by graduate student Nemiah Ladd with assistance from UW
Biology undergraduate June Landenburger.
Our first mangroves were planted
in our lab in July, 2011 with propagules of Rhizophera apiculata that
we collected in Pohnpei, Micronesia. The figure on the left
shows the outside of 3 of the growing tanks, covered with plastic to maintain
high humidity. There is a mock tidal cycle with two high and two low
tides per day. The figure on the right shows the inside of the
15 PSU salinity tank on October 3, 2011. The largest plants are Rhizophera
apiculata. There are also Rhizophera mangle and Laguncularia
racemosa plants growing in this tank, from propagules and seeds from
Florida. If you look closely you can also see some Xylocarpus
granatum seeds that have roots, but no shoots yet. These were
collected in Kosrae, Micronesia in September, 2011.
In
order to expand the number of plants and salinities we could maintain, and
better control temperature and humidity, we moved our mangrove experiments to
the University of
Washington Botany Greenhouse in mid-2012. As of December, 2012 we
have 6 species of mangroves growing at 6 different salinities (see below
images).
The large number of species are required in order to evaluate the mechanisms
responsible for hydrogen isotope fractionation in mangrove lipids as a
function of salinity since three different strategies for managing salt are
employed by mangroves, alone or in combination. The images below are
from October 11, 2012. Below left you can see tall shoots of Heritiera
littoralis (from Honolulu, HI) and young Rhizophera apiculata (from
Pohnpei, FSM) plants. Below right you can see shoots of Xylocarpus
granatum amongst young Rhizophera apiculata plants, both of which
were collected in Pohnpei, Micronesia in August 2012.
 
- Field Studies: Yap, Chuuk, Pohnpei
& Guam (2012), Station ALOHA Cruise, R/V
Thomas G. Thompson (2012), NE Pacific Cruise, R/V Point Sur
(2012), Brisbane River
(2010), Saline Lakes of
Canada's Western Great Plains & Utah's Great Salt Lake (2007),
Cargill-Newark Salt
Works (2008), Christmas Island
(2005), Chesapeake Bay (2006)
- Publications:
- Zhang, Nelson, Sachs (2014). Hydrogen isotope fractionation in algae: III. Theoretical interpretations. Organic Geochemistry Vol. 75: 1-7.
- Nelson & Sachs (2014). The influence of salinity on D/H fractionation in dinosterol and brassicasterol from globally distributed saline and hypersaline lakes. Geochimica et Cosmochimica Acta Vol. 133: 325-339.
- Zhang, Metzger, Sachs (2014). Bound lipid biomarkers in sediments from El Junco Lake, Galápagos Islands. Organic Geochemistry Vol. 75: 122-128.
- Nelson & Sachs (2014). The influence of salinity on D/H fractionation in alkenones from saline and hypersaline lakes in continental North America. Organic Geochemistry Vol. 66: 38-47.
- Atwood, Volkman, Sachs (2014). Characterization of unusual sterols and long chain diols, triols, keto-ols and n-alkenols in El Junco Lake, Galápagos. Organic Geochemistry Vol. 66: 80-89.
- Sachs (2014). Hydrogen Isotope Signatures in the Lipids of Phytoplankton In: Falkowski, P, and Freeman, K. (Ed.), Treatise on Geochemistry, 2nd Edition Elsevier, Oxford: pp. 79-94.
- Ladd & Sachs (2013). Positive correlation between salinity and n-alkane δ13C values in the mangrove Avicennia marina. Organic Geochemistry Vol. 64: 1-8.
- Nelson, & Sachs (2013). Concurrent purification of sterols, triterpenols and alkenones from sediments for hydrogen isotope analysis using high performance liquid chromatography. Organic Geochemistry Vol. 64: 19-28.
- Zhang, Metzger, Sachs (2013). Unprecedented long-chain 1-chloroalkenes and 1-chloroalkanes in the Holocene sediments of Lake El Junco, Galapagos Islands. Organic Geochemistry Vol. 57:1-6.
- Ladd & Sachs (2012) Inverse
relationship between salinity and n-alkane δD values in the mangrove Avicennia
marina. Organic Geochemistry Vol. 48:
25-36.
- Atwood & Sachs (2012) Purification of
dinosterol from complex mixtures of sedimentary lipids for hydrogen
isotope analysis. Organic Geochemistry
Vol. 48: 37-46.
- Sachse et al. (2012). Molecular paleohydrology:
Interpreting the hydrogen-isotopic composition of lipid biomarkers
from photosynthesizing organisms. Annual
Review of Earth and Planetary Sciences, 40: 221-249
- Sachs & Schwab (2011) Hydrogen isotopes
in dinosterol from the Chesapeake Bay estuary.
Geochimica et Cosmochimica Acta Vol. 75(2): 444-459.
- Schwab & Sachs (2011) Hydrogen isotopes
in individual alkenones from the Chesapeake Bay estuary.
Geochimica et Cosmochimica Acta, 75(23): 7552–7565.
- Schwab & Sachs (2009) The
measurement of D/H ratios in alkenones and their isotopic
heterogeneity. Organic Geochemistry Vol. 40: 111-118.
- Zhang, Z., J.P. Sachs, A. Marchetti (2009) Hydrogen
isotope fractionation in freshwater and marine algae: II. Temperature
and nitrogen-limited-growth-rate effects. Organic Geochemistry
Vol. 40(3): 428-439.
- B_hring, S.I., R.H. Smittenberg, D. Sachse, J.S.
Lipp, S. Golubic, J.P. Sachs, K.-U. Hinrichs, R.E. Summons (2009)
"A
hypersaline microbial mat from the Pacific Atoll Kiritimati: insights
into composition and carbon fixation using biomarker analyses and a
13C-labeling approach." Geobiology 7: 1-16.
- Bowman & Sachs (2008) Chemical
and physical properties of some saline lakes in Alberta and
Saskatchewan, Saline Systems. Vol. 4:3.
- Sachse & Sachs (2008) Inverse
relationship between D/H fractionation in cyanobacterial lipids and
salinity in Christmas Island saline ponds, Geochimica
et Cosmochimica Acta Vol.72: 793-806.
- Zhang & Sachs (2007) Hydrogen
isotope fractionation in freshwater algae: I. Variations among
lipids and species, Organic Geochemistry Vol. 38: 582-608.
- Smittenberg & Sachs (2007) Purification
of dinosterol for hydrogen isotopic analysis using high-performance
liquid chromatography-mass spectrometry. Journal of
Chromatography A, 1169(1-2), 70-76.
- Englebrecht & Sachs (2005) Determination of sediment provenance at drift
sites using hydrogen isotopes and unsaturation ratios in alkenones, Geochimica et Cosmochimica Acta Vol. 69(17): 4253-4265
- El Niño & Peru Upwelling from
Mollusks
JISAO Postdoctoral Fellow, Matthieu Carré
(now CNRS Charg_s de Recherche at Univ. of Montpellier, France), is using
oxygen and carbon stable isotopes in mollusk shells from middens along the
coast of Peru to reconstruct the history of upwelling and El Ni_o during the
Holocene.
- Carré, Sachs, Purca, Schauer, Braconnot, Falcón, Julien, Lavallée (2014) "“Holocene history of ENSO variance and asymmetry in the eastern tropical Pacific”. Science. Published online Aug. 7, 2014.
- Carré, Sachs, Schauer, Rodriguez (2013).“Reconstructing El Niño-Southern Oscillation activity and ocean temperature seasonality from short-lived marine mollusk shells from Peru.” Palaeogeography, Palaeoclimatology, Palaeoecology. Vol. 371: 45-53.
- Carre, Azzoug, Bentaleb, Chase, Fontugne, Jackson,
Ledru, Maldonado, Sachs, Schauer (2012) Mid-Holocene mean
climate in the south eastern Pacific and its influence on South
America. Quaternary International Vol. 253: 55-66.
- Sadler, Carré, Azzoug, Schauer, Ledesma, Cardenas,
Chase, Bentaleb, Müller, Mandeng, Rohling, Sachs (2012). Reconstructing past
upwelling intensity and the seasonal dynamics of primary productivity
along the Peruvian coastline from mollusk shell stable isotopes.
Geochemistry, Geophysics, Geosystems, 13(1): Q01015.
doi:10.1029/2011GC003595.
- Carré, Sachs, Wallace, Favier (2012). Exploring errors in
paleoclimate proxy reconstructions using Monte Carlo simulations:
paleotemperature from mollusk and coral geochemistry.
Climate of the Past, 8: 433-450.
- Deep ocean oxygen, carbon
storage & the biological pump
- Anderson, Barker, Fleisher, Gersonde, Goldstein, Kuhn, Mortyn, Pahnke, Sachs (2014) "“Biological response to millennial variability of dust and nutrient supply in the Subantarctic South Atlantic Ocean”. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. Vol. 372: 20130054.
- Bradtmiller, Anderson, Sachs, Fleisher (2010)
"A
deeper respired carbon pool in the glacial equatorial Pacific Ocean."
Earth and Planetary Science Letters Vol. 299(3-4): 417-425.
- Anderson, Chase, Fleisher, Sachs (2002). "The
Southern Ocean's biological pump during the Last Glacial Maximum."
Deep-Sea Research, Part II Vol. 49: 1909-1938.
- Carré, Sachs, Purca, Schauer, Braconnot, Falcón, Julien, Lavallée (2014) "“Holocene history of ENSO variance and asymmetry in the eastern tropical Pacific”. Science. Published online Aug. 7, 2014.
- Leduc, Sachs, Kawka, Schneider (2013) "Holocene changes in eastern equatorial Atlantic salinity as estimated
by water isotopologues." Earth and Planetary Science Letters Vol. 362: 151-162.
- Carré, Azzoug, Bentaleb, Chase, Fontugne, Jackson,
Ledru, Maldonado, Sachs, Schauer (2011) Mid-Holocene
mean climate in the south eastern Pacific and its influence on South
America. Quaternary International In Press, Corrected
Proof.
- Koutavas & Sachs (2008) Northern
timing of deglaciation in the eastern equatorial Pacific from alkenone
paleothermometry, Paleoceanography Vol. 23: PA4205,
doi:10.1029/2008PA001593.
- Pahnke & Sachs (2006) "Sea
surface temperatures of southern middle-latitudes 0-160 ky BP."
Paleoceanography Vol. 21: PA2003, doi:10.1029/2005PA001191
- Sachs & Anderson (2003) "Fidelity
of alkenone paleotemperature reconstructions in southern Cape Basin
sediment drifts" Paleoceanography Vol. 18(4): 1082.
- Stenni et al. (2003) "A
late-glacial high resolution site and source temperature record
derived from the EPICA Dome C isotope records (East Antarctica)."
Earth and Planetary Science Letters Vol. 217: 183-195.
- Koutavas, Lynch-Stieglitz,
Marchitto, Sachs (2002) "El
Ni_o–like pattern in Ice Age tropical Pacific sea surface temperature."
Science Vol. 297: 226-230.
- Lehman, Sachs, Crotwell, Keigwin, Boyle (2002).
"Relation
of subtropical Atlantic temperature, high latitude ice rafting, deep
water formation, and European climate 135,000-60,000 years ago."
Quaternary Science Reviews 21: 1917-1924.
- Sachs, Anderson & Lehman (2001) "Glacial
surface temperatures of the southeast Atlantic Ocean." Science
Vol. 293: 2077-2079.
- Sachs & Lehman (1999) "Subtropical
North Atlantic temperatures 60,000 to 30,000 years ago." Science
Vol. 286: 756-759.
- Holocene cooling of the
Northwest Atlantic Ocean
- The origin of fine particles in
sediment drifts
o
- Eastern Mediterranean sapropels
- Nitrogen & carbon isotopes
in chlorophyll
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People
 Julian
Sachs
- Professor of Oceanography
 Matthew Wolhowe - NSF Postdoctoral Fellow
 Ashley Maloney - Graduate Student, UW Program on
Climate Change Fellow, Global Change IGERT Fellow
 Jiwoon Park - Graduate Student
Tess Clinkingbeard - Graduate Student
 Becci Danford - Undergraduate Student
 Polly Sobeck - Undergraduate Student
Amanda Witt - Undergraduate Student
Lab Alumni
 Josh Gregersen - Research Scientist/Engineer 3
 Lauren Brandkamp - Research Scientist/Engineer 1
 Alyssa Atwood - Graduate Student, NSF Graduate
Fellow, DOE Graduate Fellow (PhD 2015. Presently NOAA Postdoctoral Fellow at UC-Berkeley & Georgia Tech.)
 Nemiah Ladd - Graduate Student, NSF Graduate Fellow (PhD 2014. Presently NSF Postdoctoral Fellow at EAWAG, Switzerland)
 Tessa McGee - Graduate Student (MS 2016)
 Marta Wolfshorndl - Graduate Student (MS 2016)
 Dan Nelson - Graduate
Student (PhD 2014. Currently Postdoc at Univ. Basel, Switzerland)
Kathleen Hemeon - Research Aide I,
Phytoplankton Specialist
 Dr. Julie Richey - NOAA Postdoctoral Fellow
 Dr. Avery Cook Shinneman - Postdoctoral
Investigator
 Dr. Ines Mügler - Humboldt Postdoctoral Fellow
 Dr. Orest
Kawka - Lab Manager / Research Scientist II
 Amanda Chomos, Laboratory Assistant
 Dr. Juzhi Hou - UW PCC Postdoctoral Fellow
 Dr. Matthieu Carre
- JISAO Postdoctoral Fellow
 Brittany Demianew - Research Scientist I
 Dr. Valerie Schwab
- Swiss NSF Postdoctoral Fellow
 Dr.
Dirk Sachse
- Humboldt Postdoctoral Fellow
 Dr. Rienk Smittenberg
- Comer Postdoctoral Fellow
Dr. Katharina Pahnke
- Comer Postdoctoral Fellow
Dr.
Zhaohui Zhang - Comer Postdoctoral Fellow
Casey
Saenger - Graduate Student
Former Undergraduate Researchers
 Colton Skavicus - Undergraduate Student
 Kesley Price - Undergraduate Student
 Elise Baldwin - Undergraduate Student
Samantha Hing - Undergraduate Student
Cyrena Thibodeau - Undergraduate Student
 Johnny Huynh - UW Oceanography Undergraduate, Mary
Gates Scholar
Lauren Brandkamp - UW Oceanography Undergraduate
 Chris Paschall - UW Oceanography Undergraduate
 June Landenburger - UW Biology Undergraduate
Ryan D'Jay - UW Oceanography Undergraduate
 Conor Myhrvold - Princeton Undergrad., MIT
Science Writing Graduate Student
 Tory Johnson - UW Undergraduate
 Thien-Y, Le - UW Undergraduate
 Jake Zaragoza - JISAO Summer Intern / Gonzaga Univ.
Undergraduate
 Kyle Thomas - Texas Southern University
Undergraduate, NOAA/JISAO Intern
 Fran Janny - UW Undergraduate
 Jeff Bowman
- Levinson & Mary Gates Scholar
Jane Lee
Eric Battisti
Brittany Demianew
Carie Frantz
Evan Howard
Brittany Kimball
Daniel Luksic
Jen Nomura
Former High School Interns
 David Golub - Interlake High School Gifted
Student Intern
 Nathan Kato - Interlake High School Gifted Student
Intern
Lab Photos
(We like to snowboard & ski!)
 Koror, Palau -- October 2016
 Stevens Pass - March 19, 2014
L to R: Lei, Marta, Tessa, Ashley, Nemiah, Julian
 Mount Baker - March 25, 2012
L to R: Dan, Ashley, Julian, Josh
 Crystal Mountain - March 29, 2011
L to R: Julian, Dan, Avery, Julie, Mat, Ashley
 Ashley & Julie on SHENDA - Nov 2, 2010
 Crystal Mountain - March 15, 2010
L to R: Alyssa, Julian, Dan, Nemiah, Sarah, Jesse
 Crystal Mountain - April 5, 2009
L to R: Julian, Dan, Mt. Rainier, Alyssa, Orest
 Mt. Baker Powder Day - March 31, 2008
L to R: Alyssa, Julian, Dan
 Mt. Baker Powder
Day - April 11, 2007
L to R: Orest, Rienk, Valerie, Matthieu, Julian, Dirk
 Steven's Pass Powder Day - March 9, 2006
L to R: Luzzi, Valerie, Julian, Dirk, Rienk
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