Monthly Kachemak Bay Report, July 2026
Summary
It has been cold. Throughout the water column, temperatures were colder than normal, by over 2.5 standard deviations in some places. Chlorophyll concentrations were high in some locations near the surface, but were below normal overall.High levels of surface turbidity were encountered at several inner bay sites, reflecting heavy rainfall during the week of the survey. However near-surface, inner-bay salinities were still close to the seasonal mean, indicating that recent rain runoff had not yet mixed deeper than 1 meter in the water column.
A complete set of up-to-date graphs can be found on this Google Drive: section plots and time sections (request access from martin.renner@noaa.gov).
Conditions
Air temperatures leading up to this survey cooler than normal, but within one standard deviation of the long-term mean (Figure 1). After a dry June, mid July was wet, with major precipitation falling between the first and last day of this survey.
Results are shown for the Kasitsna Bay Lab oceanographic survey conducted on 17, and 22 July 2026 by Jen, Kris and Martin in calm conditions.
Physical oceanography
Temperature
Water temperatures during the July survey ranged from a minimum of 6.0 °C at station AlongBay-12 (65 m depth), in the inner bay, to a maximum of 11.1 °C at station AlongBay-9 (1 m depth) in the inner bay. Strong vertical stratification was observed throughout the bay, with a shallow layer of warmer, fresher surface water over cooler, more saline waters below (Figure 2 (a), top-left panel). Stratification was less pronounced in the outer bay. Surface waters were warmer and bottom waters were colder in the inner than in the outer bay. Satellite sea surface temperature data with a cooler pool of 8-9 °C waters in lower Cook Inlet (Figure 3).
Throughout the bay, and at all depth, waters were colder than normal, in some areas by over 2.5 standard deviations (Figure 2, top-right panel, Figure 6, Figure 8). Most of Kachemak Bay was about 1 °C colder than normal. Surface waters in mid-bay of Homer Spit and in Homer Harbor were near or slightly cooler than normal (Figure 4, Figure 5). Deep waters, however, remained substantially colder than normal (one standard deviation and more), a pattern that has persisted since last December (Figure 6). Surface waters of the Gulf of Alaska and Bering Sea also remained colder than normal in July 2026, as shown by satellite sea temperature anomaly data, in contrast to the extremely warm conditions in the central North Pacific (Figure 7).
Salinity
Salinity values during the July survey ranged from 18.3 PSU at station AlongBay-11 (1m depth) in the inner bay to 31.6 PSU at station AlongBay-3 (69m depth) in the outer bay. The water column was strongly stratified, especially in the inner bay, with fresher waters in a 10-20 m surface layer (Figure 2).
Most Kachemak Bay near-surface waters were close to or slightly saltier than normal (Figure 2, Figure 8). We could see the effects of heavy rainfall runoff in the high surface turbidity in the inner bay (@turb). However, since the CTD sensors only start measuring at 1 meter depth and seas were calm, we likely did not capture the freshest inner bay surface water during this survey. At depth, outer bay waters were near the long-term mean and continued to be fresher than normal in the inner bay (Figure 2, Figure 8, Figure 9).
Turbidity
High surface turbidity was encountered at several stations from mid-bay to Bear Cove (Figure 10). Inner bay waters were more turbid than outer bay waters, with highest levels found in the thin rain-driven fresher surface layer of the inner bay (Figure 2 (a)). In contrast, outer bay waters were unusually clear for this time of year.
Biological conditions
Phytoplankton
Elevated chlorophyll concentrations were found in the upper 20 meters throughout Kachemak Bay, with the highest values near the seaward extent of the fresher surface layer in the outer bay (Figure 2 (a)). Integrated over the entire water column, chlorophyll concentrations were expected to drop slightly from June to July, but decreased from near the long-term mean in June to almost a full standard deviation below the mean in July (Figure 11). Our partners from the Kachemak Bay National Estuarine Research Reserve detected potentially toxic Pseudo-nitschia spp. as “present” in most samples, apart from T9-6 in the mid-bay, which was recorded as “bloom” and AlongBay-10, where it was “abundant”. Also potentially toxic Alexandrium spp. cells were detected as “present” in mid-bay, at the head of the bay, and near the mouth of the bay (Kim Schuster, Kachemak Bay NERR, The Phyto Times, 23 July 2026).
Wildlife
A humpback whale and a pod of seven orcas were in the outer bay (Figure 12). Sooty shearwaters and fork-tailed storm-petrels were seen in the bay for the first time this year, with small numbers in the outer bay. Other birds of note in the outer bay were a northern fulmar and a horned puffin, and over a hundred red-necked phalaropes.
Mailing list
Please email Martin at martin.renner@noaa.gov if you would like to be added to or removed from this mailing list.
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