11th Symposium on Lidar Atmospheric Applications Paper #: 5.6

Ocean subsurface study from ICESat-2 Mission

Xiaomei Lu (SSAI/NASA LaRC), Yongxiang Hu (NASA LaRC), Yuekui Yang (NASA Goddard)

Acknowledgments: • supported by CALIPSO/CloudSat science team and Dr. David Considine of NASA HQ • supported by Dr. Jack Kaye for the year-end support on the ICESat-2 ocean research

Jan. 12, 2021, 1:55PM-2:00PM (EST) Outline 1. Ocean research from ICESat-2 lidar § Ocean subsurface Profiles at very high vertical resolution § Antarctic spring ice-edge blooms § Seasonal cycles of Antarctic ocean biology § Ocean biology – atmosphere cloud interaction

2. Summary ICESat-2 Ocean subsurface vertical profiles ICESat-2 Ocean Results DepthDepth-resolved-resolved structure structurenot bypreviously ICESat -available2 from passive Depth-resolvedVertical profiles structure over Arabian by ICESat seasensor not-2 previously not previously available available from passive from passive sensor sensor Ocean subsurface attenuated backscatter profiles (m-1 sr-1)

Lu, et al. (2019). Ocean Subsurface Study from ICESat-2 Mission. In 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall)Lu, (pp.et al. 910(2019).–918). Ocean https:// Subsurfacedoi.org Study/10.1109/PIERS from ICESat-2 Mission.-Fall48861.2019.9021802 In 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) (pp. 910–918). Lu, https://et al.,doi.org 2020,/10.1109/PIERS ‘Antarctic spring-Fall48861.2019.9021802 ice-edge blooms observed from space by ICESat-2.’ of Environment, 194, p 248-263. https://Lu, etdoi.org al., 2020,/10.1016/j.rse.2020.111827 ‘Antarctic spring ice-edge blooms observed from space by ICESat-2.’ Remote Sensing of Environment, 194, p 248-263. https://doi.org/10.1016/j.rse.2020.111827 Antarctic spring ice-edge blooms (X. Lu, Y. Hu, et al. 2020) Antarctic spring ice-edge blooms (X. Lu, Y. Hu, et al. 2020) First observations of depth-resolved structure of ice-edge First observations ofblooms depth-resolved by ICESat structure-2 by ICESat-2 PhotonsICESAT altitude-2 signal on 2018-10-16 ltitude(m) A Ocean subsurface attenuated backscatter (m-1 sr-1)on 2018-10-16

Phytoplankton carbon biomass (mg/m3) on 2018-10-16

Phytoplankton blooms Altitude in water (m) water in Altitude observed below ocean surface near ice-edge Lu, et al, 2019, Science Lu, et al., 2020, ‘Antarctic spring ice-edge blooms observed from space by ICESat-2.’ Remote Sensing of Environment, 194, p 248-263. Lu, et al., 2020, ‘Antarctic spring ice-edge blooms observed from space by ICESat-2.’ Remote Sensing of Environment, 194, p 248-263. SeasonalSeasonal cycles cycles ofof Antarctic Antarctic ocean ocean biology biology

ICESatICESat-2 provide-2 provide ocean ocean biology biology results results throughout throughout thethe yearyear at highhigh latitudelatitude where where MODIS MODIS has limited observations. has limited observations. SeasonalSeasonal pattern pattern of of oceanic oceanic bbbpbpinin polarpolar regions

ICESat-2 results

MODIS results

The space lidar fills observation gap of ocean biology when obscured by optically thin cloud and sea ice. The space lidar fills observation gap of ocean biology when obscured by optically thin cloud and sea ice. Lu, et al., 2020, ‘Antarctic ocean biological activity response to sea ice changes and its impact on cloud microphysics.’ under revising, PNAS. Lu, et al., 2020, ‘Antarctic ocean biological activity response to sea ice changes and its impact on cloud microphysics.’ in prepare, PNAS. Investigations of sea ice, cloud and oceanic processes in the Southern Ocean from ICESat-2 mission (Kern et al., 2016). Figure 8 provides the spatial and seasonal patterns of CALIOP subsurface depolarization ratio during both daytime and nighttime estimated using the method in (Lu et al., 2014). The subsurface depolarization ratio is a key component of the CALIOP ocean data product which can be used for the phytoplankton particle’s shape studies (e.g. spherical or non-spherical particles). The sea ice contours in Fig. 7 and 8 are shown as solid white lines (50% concentration) and black dash lines (1% concentration). Figure 7 and 8 indicate that the marine biological activity is closely linked to the seasonal sea ice cycles. The ocean results from both ICESat-2 and CALIOP lidar will be used for the sea ice melting – ocean biology interaction study in proposed climate feedbacks shown in Fig. 6. The day and night differences of oceanic optical properties (e.g., Fig.8) can be used to measure the vast animal migration that happens daily from the countless small sea creatures in the Earth’s ocean (Behrenfeld et al., 2019). If funded, the marine biology results below sea ice during both day and night through all seasons will be analyzed over the entire ICESat-2/CALIOP missions, especially the austral wintertime when passive ocean color have very limited observations due to the sea ice coversSeasonal Seasonalas shown in lowe cycles cyclesr panels ofof Fig. Antarctic Antarctic 7. Compared ocean with ocean passive biology ocean biology color records, the Space lidar, ICESat-2 and CALIOP fill observation gap of marine biology obscured by optically thin cloudICESat andICESat- 2sea provide- 2ice. provide ocean ocean biology biology results resultsthroughout throughout the year theat high year latitude at high where latitude MODIS where has MODIS limited observations. has limited observations.Seasonal patternSeasonalSeasonal of pattern phytoplankton pattern of of oceanic oceanic bb bpinbpinin polar polarpolar regionsregions

ICESat-2 results

SeasonalSeasonal cycles cycles ofof Antarctic Antarctic ocean ocean biology biology MODIS results ICESatICESatICESat-2 provide-2 provide-2 oceanocean ocean biology biology biology results vs. resultsthroughoutCALIOP throughout the subsurface year theat high year latitude atdepolarization high where latitude MODIS where has MODIS limited observations. has limited observations. SeasonalSeasonal pattern pattern of of oceanic oceanic bbbpbpinin polarpolar regions

ICESatICESat-2 results-2 bbp FigureNighttimeThe 7. Upper space panels:lidar fills Seasonal observation results gap of of ICESat ocean biology-2 retriev whened integrated obscured bybbp optically(/m). The thin sea cloud ice contours and sea areice. The space lidar fills observation gap of ocean biology when obscured by optically thin cloud and sea ice. shownLu as, etsolid al., 2020, white ‘Antarctic lines ocean(50% biological) and black activity dashresponse lines to sea (1% ice changes). Spring: and itsSep., impact Oct., on cloud Nov.; microphysics.’ Summer: under Dec., revising, Jan.,PNAS Feb.;. Lu, et al., 2020, ‘Antarctic ocean biological activity response to sea ice changes and its impact on cloud microphysics.’ under revising, PNAS. Fall: Mar., Apr., May.; Winter: Jun., Jul., Aug. Lower panels: The corresponding MODIS bbp results. The color is value of bbp. Seasonal pattern of subsurface ! from space lidar, CALIOP

MODIS results CALIOP depo Nighttime

The space lidar fills observation gap of ocean biology when obscured by optically thin cloud and sea ice. The spaceCALIOP lidar fillsdepo observation gap of ocean biology when obscured by optically thin cloud and sea ice. Lu, Daytimeet al., 2020, ‘Antarctic ocean biological activity response to sea ice changes and its impact on cloud microphysics.’ under revising, PNAS. Lu, et al., 2020, ‘Antarctic ocean biological activity response to sea ice changes and its impact on cloud microphysics.’ under revising, PNAS.

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Ocean biology – cloud interaction over Antarctic ocean

ICESat-2 ocean

CALIOP Cloud

Cloud droplet number density

particle size

OceanOcean biology biology – –cloudAtmosphere interaction cloud over interaction Antarctic ocean

Two independent Space-lidar measurements Strong relation found between two independent Space-lidar measurements CALIOP cloud vs. ICESat-2 ocean bbp CALIOP cloud vs. ICESat-2 ocean bbp ) 3 - CALIOP Nd (cm Nd CALIOP

-1 size(um) particle CALIOP -1 ICESat-2 bbp (m ) ICESat-2 bbp (m ) ScienceFig. investigationsFig. 3. Biogenic 3. Biogenic influence influence to improve on oncloud cloud ourNd Nd and understanding and Re Re over over the the entire entire of Antarctic oceanAntarctic- atmosphereocean. ocean. (A) (A) CALIOP CALIOP interactions NdNd Science -(cminvestigations3 -3, y-axis) vs. ICESat to- 2improve ocean b (m-our1 -1, x understanding-axis). (B) CALIOP Re of (µm, ice y--oceanaxis) vs. -ICESatatmosphere-2 and their(cm impact, y-axis) on vs. theICESat climate.-2 ocean bbp (mbp , x-axis). (B) CALIOP Re (µm, y-axis) vs. ICESat-2 -1 interactionsocean andbbp- 1(m their, x-axis). impact The data on are the averaged global monthly climate. over 1° latitude ´ 1° longitude bins. The Hu, et al.,ocean 2007, Globalbbp (m statistics, x-axis). of liquid The water data content are averaged and effective monthly number concentrationover 1° latitude of water ´ 1clouds° longitude over ocean bins. The 5 colors represent the numbers of observations and R is the correlation coefficient with negative 5derived fromcolors combined represent CALIPSO the andnumbers MODIS ofmeasurements. observations Atmos. and Chem.R is thePhys. correlation7, 3353–3359 coefficient . with negative Lu, et al., 2020,value ‘Antarctic means ocean anticorrelation biological activity (or responsenegative to correlation). sea ice changes and its impact on cloud microphysics.’ in value means anticorrelation (or negative correlation). prepare, PNAS .

Clouds respond to sea ice melting/retreat Clouds respond to sea ice melting/retreat The Antarctic sea ice melting in spring and summer increases ocean biological activity The Antarctic sea ice melting in spring and summer increases ocean biological activity 10 (Fig. 1), leading to subsequent increases of Nd and decreases of Re (Fig. 3). Because clouds 10 (Fig.heavily 1), leading influence to subsequent the surface increases energy budget of Nd (and35), decreasesthe coupling of Rebetween (Fig. 3).sea Becauseice and clouds clouds is of heavilyparticular influence importance. the surface Figure energy 4 shows budget the (response35), the couplingof clouds betweenmicrophysics sea ice to andsea iceclouds melting is of particularover the importance. entire Antarctic Figure ocean 4 shows from the 2007 response to 2017. of Fi cloudsgure 4A microphysics shows the CALIOP to sea ice monthly melting Nd overanomaly the entire (cm Antarctic-3, y-axis) ocean vs. the from monthly 2007 seato 2017.ice area Fi gureanomaly 4A shows(%, x- axis);the CALIOP Fig. 4B showsmonthly the Nd -3 15 anomalyCALIOP (cm monthly, y-axis) Re vs. anomaly the monthly (µm, ysea-axis) ice vs.area the anomaly monthly (%, sea x ice-axis); area Fig.anomaly 4B shows (%, x -theaxis); 15 CALIOPand Fig. monthly 4C plots Re the anomaly monthly (µm, Re anomalyy-axis) vs. (y -theaxis) monthly vs. monthly sea ice Nd area anomaly anomaly (x-axis). (%, x The-axis); red and linesFig. 4Cin Fig. plots 4 arethe linearmonthly fittings Re anomaly of the paired (y-axis) anomalies vs. monthly (blue dots)Nd anomaly with R showing(x-axis). the The red linescorrelation in Fig. 4 are coefficients linear fittings. The figuresof the paired demonstrate anomalies the degree (blue dots)to which with sea R iceshowing melting the (negative x- correlationaxis values) coefficients is accompanied. The figures by increases demonstrate of cloud the Nddegree and decreasesto which seaof cloud ice melting Re. These (negative Nd and x - 20 axisRe values) variations is accompanied over the Antarctic by increases ocean canof cloud largely Nd be and attributed decreases to seasonalof cloud changes Re. These in oceanNd and 20 Re variationsbiological overactivity. the AntarcticAs described ocean above, can thelargely melting be attributed of sea ice toleads seasonal to greater changes expa nsesin ocean of the biologicalopen waters activity. that As provide described the stable above, environment the melting required of sea ice for leads the growth to greater of ocean expa phytoplankton.nses of the openFigure waters 3 thatshows provide that this the increase stable environment in phytoplankton required abundance for the leads growth to simultaneousof ocean phytoplankton. changes in Figurecloud 3 shows microphysics; that this i.e.,increase increases in phytoplankton in Nd and decrease abundances in Re leads. In addition, to simultaneous the high changes in 25 cloudconcentrations microphysics; of i.e.,algae increases found at inthe Nd bottom and decrease of ice floess in (Fig.Re. InS1) addition, can also the contribute high to changes 25 concentrationsin marine boundary of algae layerfound clouds at the during bottom melt of ice seasons. floes (Fig.Previous S1) researchcan also (contribute14) has established to changes that in marinechanges boundary in airborne layer sea clouds salt concentration during melt areseasons. insufficient Previous to explain research the ( 14spatiotemporal) has established variance that changesin Nd in and airborne Re. Based sea salton the concentration analyses presented are insufficient above, we to argue explain that the the spatiotemporal primary drivers variance of the in Ndobserved and Re .changes Based on in cloudthe analyses microphysical presented properties above, weare arguethe seasonal that the cycles primary of ocean drivers biological of the 30 observedactivity. changes in cloud microphysical properties are the seasonal cycles of ocean biological

30 activity.

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Summary

1. ICESat-2 ocean subsurface research at LaRC - augment existing ocean color records - provides both day and night ocean results at very high vertical resolutions - provide valuable ocean results over high latitude regions covered by sea ice. - ocean – aerosol – cloud interaction study.

Any questions? Welcome send me email at: xiaomei.lu@.gov