Monthly Kachemak Bay report, January 2026

Authors

Affiliations

Martin Renner

CSS, under contract to NOAA/NCCOS Kasitsna Bay Lab

Kris Holderied

NOAA/NCCOS Kasitsna Bay Lab

Paul Cziko

NOAA/NCCOS Kasitsna Bay Lab

Summary

The first half of January 2026 was cold in Kachemak Bay. Homer airport recorded its lowest air temperatures this century. Water temperatures were the coldest recorded in any January since our ocean surveys started in February 2012 (bested only that month). Outer bay temperatures and salinities showed the connection to inflows of warmer ocean water from the Gulf of Alaska, which was also colder than normal. Salinity values in Kachemak Bay were near normal after being fresher than normal for most of 2025. A complete set of up-to-date graphs can be found on this Google Drive: section plots and time sections.

Conditions

The month leading up to this survey was unusually cold. Average air temperatures at Homer airport in late December to early January were about 7 °C below the long-term mean and over 2 °C below the 10th percentile for that month (Figure 1). The low on 8 January 2026 (-24.4 °C / -12 °F) was the lowest air temperature recorded since the turn of the century, but warmed up approaching the seasonal mean in the second half of the month. Prior to the survey, strong winds and high tides had driven substantial amounts of ice out of Mud Bay. Hans, Kris, and Paul conducted the KBL monthly survey on 20 January, covering the AlongBay and mid-bay T9 transects in sea states relatively calm sea states.

Figure 1: Recent temperature at the Homer Airport, compared to the seasonal mean.

Physical oceanography

Temperature

Water temperatures during this survey ranged from a minimum of 0.6 °C at station 9-10 (2 m depth), off Homer Spit, to a maximum of 4.2 °C at station AlongBay-4 (15 m depth) in the outer bay. As expected for this month, the inner bay was colder than the outer bay, with the main transition near the Homer Spit (as indicated by the densely spaced contour lines in Figure 2 (a), top-left panel).

T9 is situated around km 30 of the AlongBay transect, cross-sectioning the inner/outer bay transition zone. Sloping salinity and temperature contour lines showed influx of warmer, more saline water at depth, especially on the south side, and an outflow of colder, fresher water on the surface at the north side of T9 (Figure 2 (b)). While the entire water column was colder than normal, the strong surface water cold anomalies found near the Spit were likely caused by melting pack ice from Mud Bay (also note the dip in salinity at the same location).

(a) AlongBay Transect from Kachemak Bay entrance (left) to Bear Cove (right).

(b) T9 Transect, across bay from Homer Spit (left) to China Poot Bay (right).

Figure 2: Along bay and cross-sections of main parameters from the current cruise (left column) and their respective anomalies, i.e. the difference between the current measurements and the long-term monthly mean (2012-current) at the respective place and depth.

On a larger scale, satellite sea surface temperature data showed how Kachemak Bay temperatures were driven by an interplay of warm waters from the Gulf of Alaska and gradual cooling as they moved into the increasingly shallow waters (Figure 3).

Figure 3: Sea surface temperature in the Gulf of Alaska, based on satellite remote sensing

Everywhere in the bay, and at all depths, water temperatures were below the long-term mean, with some parts reaching over 2 standard deviations (SD) or 3 °C below normal (top-right of Figure 2, Figure 6), making this the coldest January for water temperatures in Kachemak Bay since the beginning of our records (we do not have measurements for January 2012; only February 2012 was even colder, Figure 7). Satellite measurements indicated that sea surface temperatures in the Gulf of Alaska were also colder than normal (global SST anomaly). Globally, the Gulf of Alaska stood out as one of the few areas currently colder than normal, with most of the North Pacific remaining warmer than normal. For three years (2022-2024) temperatures in Kachemak Bay stayed remarkably close to normal, were about 1 SD above normal for most of 2025, but swung over to the cooler side in January 2026 (Figure 4, Figure 5).

Figure 4: Water temperature at the Homer Harbor SWMP station, operated by the KBNERR, at approximately 7 m depth (This is the deeper of two sensors, but is still located in the surface layer).

Figure 5: Bottom-water temperature at mid-bay CTD station T9-6 compared to the seasonal long-term mean.

Figure 6: Bottom water temperature at the outer Kachemak Bay (station AlongBay-5).

Figure 7: Long-term temperature and salinity profiles at mid-bay (T9-6).

Salinity

Salinity values ranged from 28.1 PSU at 9-9 (1m depth) near Homer Spit to 31.6 at 9-6 (92m depth) in the mid-bay. Inner bay waters were fresher than outer bay waters. The outer bay was more saline than the inner bay, but in contrast to many other years, much of the water column was still stratified. Signs of a fully mixed water column were evident in the western outer bay (Figure 2 (a)). Since this fall, salinity swung from being fresher than normal for the first two-thirds of 2025 to being saltier last fall, but returned to close to normal in January 2026 (Figure 8).

Figure 8: Variability of deep-water salinity at T9-6 compared to the seasonal long-term mean.

Turbidity

No major spatial differences in turbidity levels were noted, nor were turbidity levels consistently away from expected values (Figure 2).

Biological conditions

Phytoplankton

Chlorophyll concentrations were close to zero throughout Kachemak Bay, showing no areas of concentrated activity, as may be expected during January, and especially with temperatures this cold (Figure 2, Figure 9).

Figure 9: Trends and seasonal anomaly of Chlorophyll concentrations at T9-6 (mean from surface to 85 m depth)

Mailing list

Please email Martin at martin.renner@noaa.gov if you would like to be added to or removed from this mailing list.