The Response of Ocean Skin Temperature to Rain: Observations and Implications for Parameterization of Rain-Induced Fluxes

Rainfall alters the physical and chemical properties of the surface ocean, and its effect on ocean skin temperature and surface heat fluxes is poorly represented in many air-sea interaction models. We present radiometric observations of ocean skin temperature, near-surface (5 cm) temperature from a towed thermistor, and bulk atmospheric and oceanic variables, for 69 rain events observed over the course of 4 months in the Indian Ocean as part of the DYNAMO project. We test a state-of-the-art prognostic model developed by Bellenger et al. (2017, https://doi.org/10.1002/2016JC012429) to predict ocean skin temperature in the presence of rain, and demonstrate a physically motivated modification to the model that improves its performance with increasing rain rate. We characterize the vertical skin-bulk temperature gradient induced by rain and find that it levels off at high rain rates, suggestive of a transition in skin-layer physics that has been previously hypothesized in the literature. We also quantify the small bias that will be present in turbulent sensible heat fluxes parameterized from ocean temperature measurements made at typical “bulk” depths during a rain event. Finally, a wind threshold is observed above which the surface ocean remains well-mixed during a rain event; however, the skin temperature is observed to decrease at all wind speeds in the presence of rain. Keywords: Precipitation, Ocean Skin Temperature, Sea Surface Temperature, Rain Layers, Rain Heat Flux, Flux Parameterizatio

Thin ice, deep snow and surface flooding in Kotzebue Sound: landfast ice mass balance during two anomalously warm winters and implications for marine mammals and subsistence hunting

The inaugural data from the first systematic program of sea ice observations in Kotzebue Sound, Alaska, in 2018 coincided with the first winter in living memory when the Sound was not choked with ice. The following winter of 2018-19 was even warmer and characterized by even less ice. Here we discuss the mass balance of landfast ice near Kotzebue (Qikiktagruk) during these two anomalously warm winters. We use in-situ observations and a 1-D thermodynamic model to address three research questions developed in partnership with an Indigenous Advisory Council. In doing so, we improve our understanding of connections between landfast ice mass balance, marine mammals, and subsistence hunting. Specifically, we show: i) Ice growth stopped unusually early due to strong vertical ocean heat flux, which also likely contributed to early start to bearded seal hunting; ii) Unusually thin ice contributed to widespread surface flooding. The associated snow ice formation partly offset the reduced ice growth, but the flooding likely had a negative impact on ringed seal habitat; iii) Sea ice near Kotzebue during the winters of 2017-18 and 2018-19 was likely the thinnest since at least 1945, driven by a combination of warm air temperatures and a persistent ocean heat flux.

Data for: The Response of Ocean Skin Temperature to Rain: Observations and Implications for Parameterization of Rain-Induced Fluxes

Observations of surface atmosphere and ocean variables during 68 rain events observed over the course of September-December 2011 on R/V Revelle in the Indian Ocean as part of the DYNAMO experiment. Also included are infrared and polarimetric images of a rain event observed in 2016 in the Timor Sea from R/V Falkor. This data is used in the submitted manuscript of the same name in Geophysical Research Letters

LDEO Longwave and Shortwave Downwelling Radiation on R/V Falkor cruise FK191120

Measurements of longwave (LW; Kipp & Zonen CGR4) and shortwave (SW; Kipp & Zonen CMP22) downwelling radiation were made from the top of R/V Falkor’s main mast throughout cruise FK191120 (https://schmidtocean.org/cruise/studying-the-sea-surface-microlayer-2/), from Nov 20, 2019 to Dec 20, 2019 in Pacific waters near Fiji. Data is provided at 1Hz in a netcdf file that includes LW, SW, Time (UTC), Latitude, Longitude, Ship Heading, and units information. Keywords: Air-Sea Fluxes, Radiation, Solar Radiation, Back Radiation, Tropical Ocean Heat Flux, Insolation, Infrared Emissio

LDEO Surface Processes Instrument Platform v2 (SPIP-2) Data from R/V Falkor cruise FK191120

SPIP-2 is a drifting surface buoy that was deployed daily on cruise FK191120 (https://schmidtocean.org/cruise/studying-the-sea-surface-microlayer-2/) for a total of 26 deployments. The primary data package from SPIP-2 is provided at 1Hz in a netcdf file and includes: Latitude, Longitude, 2-D Winds, Air Pressure, Relative & Absolute Humidity, Precipitation, SW Radiation, and Tilt measurements (Maximet GMX-541); Temperature and Salinity at 10cm depth, 190cm depth, and along a vertical profiling track spanning 30-130cm depth (NBOSI CT Sensors, profiling instrument depth is also provided as a time-dependent variable). Also included in the netcdf file on separate timestamps are high-accuracy Temperature, Salinity, Pressure, and Dissolved Oxygen measurements at 65cm depth (Seabird SBE37SMP/ODO, 45s sampling interval); Significant Wave Height, Peak Wave Period, Maximum Wave Height, Wave Direction, and Wave Spread (XEOS BRIZO-DL Wavelogger, 20-minute statistics); and 3-D current profile in 95 valid 3cm vertical bins spanning 48-330cm depth (2MHz Aquadopp Current Profiler, 15-minute sampling interval, only deployed on final 11 stations of the cruise). Units are included within the netcdf file for each variable. Finally, a separate zip file contains amplitude (.a), correlation (.c) , velocity (.v), header (.hdr), and auxiliary sensor (.sen) files for each deployment of the upward-looking 2MHz Pulse-Coherent Aquadopp HR, which made along-beam velocity measurements at 20° from vertical in 25mm bins spanning 0.5-1.06m depth, used to calculate TKE dissipation. Keywords: diurnal warm layers, upper ocean stratification, ocean surface processes, upper ocean profiles, TKE dissipatio

LDEO Longwave and Shortwave Downwelling Radiation in Kotzebue, Alaska from Oct 2017 - May 2019

Measurements of longwave (Kipp & Zonen CGR4) and shortwave (Kipp & Zonen CMP22) downwelling radiation were made from a tower above the Fish & Wildlife Service building in Kotzebue, Alaska from 5 October 2017 through 18 May 2019. Location: 66.894806N, 162.601310W. The data include a timestamp (MM/DD/YYYY HH:MM), Record Number (RecordNum), Downwelling Solar radiation (Rs), CMP22 Instrument Temperature (T_cmp22), Downwelling Longwave radiation (Rl_corr), CGR4 Instrument Temperature (T_cgr4), Datalogger Temperature (panel_temp), Datalogger Input Battery Voltage (batt_volt). Units are provided in the data file. Data is provided at a sampling interval of 10 min

LDEO Ice-Tethered Observatory Data from Kotzebue Sound, Jan - Apr 2019.

Measurements of net LW and SW fluxes (Kipp & Zonen CNR2); air temperature, humidity, pressure, wind speed, and solar insolation (Gill Maximet GMX-541); under-ice water temperature, conductivity, and pressure (Seabird SBE39 and RBR Concerto); and under-ice 3D current profiles (Nortek Aquadopp HR). Location: 66.8969N, 162.6170W. Duration: January 2019 - April 2019. Data are provided in one file for each instrument, with clear headings. Sampling interval is 10 minutes for all instruments, except for the Nortek Aquadopp HR which has a sampling interval of 15 minutes

LDEO Ocean-Bottom Tripod CTD measurements from Kotzebue Sound, Sep 2017 - Jun 2019

Measurements of Conductivity, Temperature, and Pressure from a Seabird SBE37-SMP deployed at 20m depth from September 2017 - June 2019. Location: 67.0598N, 163.7957W. The data include a timestamp (MM/DD/YYYY HH:MM:SS), Conductivity (cond), Temperature (temp), Density (density), Pressure (pres), Day-of-year (yearday), QC flag (flag), Salinity (sal), and Depth (dep). Sampling interval is 30 minutes

Data For: An Improved Bio-Physical Parameterization for Radiant Heating in the Surface Ocean

All observations used in the manuscript of the same name submitted to Journal of Geophysical Research: Oceans. These include: (1) shipboard observations of atmospheric and oceanic variables from R/V Falkor in November 2019 north of Fiji; (2) floating hyperspectral surface radiometer observations made during the same November 2019 cruise; (3) processed UAV data from 2 flights on the same November 2019 cruise, with up- and down-looking pyranometers corrected for platform motion to yield albedo; (4) 140 multi-spectral depth casts with coincident Pyranometer and HPLC Chlorophyll measurements, spanning 2 cruises in the tropical Atlantic (September 2015 and August 2016 onboard R/V Meteor), 3 cruises in the Gulf of Mexico (June 2015, August 2018 and July 2019 onboard R/V Endeavour), and one cruise in the Tropical Pacific (November 2019 onboard R/V Falkor)

The Ocean's Skin Layer in the Tropics

We provide a large data set on salinity anomalies in the ocean's skin layer together with temperature anomalies and meteorological forcing. We observed an average salinity anomaly of 0.40 ± 0.41 practical salinity unity (n = 23,743), and in 83% of the observations the salinity anomaly was positive; that is, the skin layer was more saline. Temperature anomalies determined by an infrared camera were −0.23 ± 0.28 °C (upper 20-μm layer in reference to nominal 1-mm depth) and slightly warmer with −0.19 ± 0.25 °C in an upper 80-μm layer in reference to 1-m depth. In 75% of the observations, our data confirmed the presence of a cooler skin layer. Light rain rates (<4 mm/hr) induced an immediate freshening by 0.25 practical salinity unit in the skin layer without any effect in the mixed layer at 1-m depth. Vertical mixing by strong winds (12 m/s) masked freshening during a heavy rain fall (47 mm/hr) by the intrusion of saltier deeper waters, but a freshening was observed after the wind and rain calmed down. We computed density anomalies, which suggest that denser skin layers can remain afloat up to a density anomaly of 1.3 g/L, likely due to the interfacial tension between the skin layer and underlying bulk water. It implies that salinization by evaporation regulates buoyancy fluxes, a key process for the exchange of climate-relevant gases and heat between the ocean and atmosphere